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Patterns of induced microearthquakes at the Sullivan Mine, Kimberley, B.C. Coenraads, Robert Raymond 1982

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PATTERNS OF INDUCED MICROEARTHQUAKES AT THE SULLIVAN MINE, KIMBERLEY, B.C. by ROBERT RAYMOND COENRAADS A. Honours, Macquarie University, Sydney, 197 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTERS OF SCIENCE in THE FACULTY OF GRADUATE STUDIES (Department of Geophysics and Astronomy) We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA March 1982 © Robert Raymond Coenraads, 1982 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree that the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r reference and study. I f u r t h e r agree th a t permission f o r extensive copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the head of my department o r by h i s o r her r e p r e s e n t a t i v e s . I t i s understood th a t copying or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l gain s h a l l not be allowed without my w r i t t e n permission. Department of The U n i v e r s i t y of B r i t i s h Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 Date ra™ (Am m i DE-6 (3/81) ABSTRACT In June and J u l y of 1980 a 12 s t a t i o n microseismic d e t e c t i o n network was e s t a b l i s h e d over a 40 km2 area about the S u l l i v a n Mine, Kimberley, B.C. f o r the purpose of using hypocentre l o c a t i o n s of mining induced earthquakes to d e l i n e a t e the p o s i t i o n of f a u l t planes i n 3-dimensions. During the experiment 1551 microseismic events were recorded by 2 or more d i g i t a l seismographs, but only 366 events were lar g e enough to be recorded by 4 or more s t a t i o n s . A r e g i o n a l v e l o c i t y of 5.30 kms"1 was determined from c a l i b r a t i o n e xplosions and a 3-dimensional l e a s t squares type l o c a t i o n program was used. Based on explosions of known l o c a t i o n w i t h i n the mine a l o c a t i o n accuracy of 180 m i n e p i c e n t r a l p o s i t i o n and 500 m i n f o c a l depth was a t t a i n e d . Recorded microseismic a c t i v i t y occurred e n t i r e l y w i t h i n the mine bounds, centered on the a c t i v e working areas. An extremely c l o s e r e l a t i o n s h i p between l e v e l of microseismic a c t i v i t y and mining c y c l e s was observed. The seismic array at the S u l l i v a n Mine wa.s found to be u n s u i t a b l e f o r use as a geologic mapping t o o l , p a r t l y because of the lack of r e s o l u t i o n . However se v e r a l i n t e r e s t i n g features of the induced m i c r o s e i s m i c i t y have become apparent: ( i ) Influence of mining a c t i v i t y at the S u l l i v a n i s extremely l o c a l i z e d , with microearthquake a c t i v i t y confined to the working areas. ( i i ) The c o r r e l a t i o n between mine a c t i v i t y and recorded microseismic a c t i v i t y was extremely high; the m a j o r i t y of microearthquakes, i n p a r t i c u l a r the smaller events, occurred i n t h e f i r s t t e n m i n u t e s a f t e r l a r g e mine b l a s t s . T h e s e a p p e a r t o be c a v i t y r e l a x a t i o n e v e n t s . ( i i i ) T h e r e a p p e a r s t o be an a s s o c i a t i o n between t h e e p i c e n t r a l l o c a t i o n s and t h e edges o f c a v e a r e a s . The o n l y a c t i v i t y w h i c h may be a s s o c i a t e d w i t h f a u l t s o c c u r s when t h e y a r e q u i t e p r o x i m a l t o t h e c a v e e d g e s ; t h a t i s where t e n s i o n a l s t r e s s e s i n t h e h a n g i n g w a l l a r e l o c a l i z e d a l o n g t h e s e p r e - e x i s t i n g p l a n e s of weakness. ( i v ) I t i s b e l i e v e d t h a t r e g i o n a l s t r e s s c o n d i t i o n s a r e u n s u i t a b l e t o a l l o w f a u l t r e a c t i v a t i o n below t h e mine. G e o l o g i c e v i d e n c e s u g g e s t s ' t h a t t h e r e g i o n a l s t r e s s i n t h e v i c i n i t y of t h e S u l l i v a n i s e i t h e r n e u t r a l o r e x t e n s i o n a l , i n w h i c h c a s e f a u l t r e a c t i v a t i o n below t h e mine w i l l be s u p p r e s s e d by t h e l o a d r e m o v a l c a u s e d by m i n i n g . i v TABLE OF CONTENTS ABSTRACT . i i L I S T OF TABLES v i L I S T OF FIGURES ... . . . . v i i ACKNOWLEDGEMENTS X CHAPTER 1 1 1.1 I n t r o d u c t i o n 1 1.2 S e l e c t e d P r e v i o u s S t u d i e s Of M i n i n g I n d u c e d S e i s m i c i t y 4 1.3 I n t r o d u c t i o n To The 1980 S u l l i v a n Mine P r o j e c t ...... 8 1.4 P r e v i o u s S t u d i e s At The S u l l i v a n Mine 12 CHAPTER 2: The S u l l i v a n Mine ... 15 2.1 G e o l o g y And S t r u c t u r e Of Orebody 16 2.2 S t r u c t u r a l H i s t o r y 18 2.3 S e t t i n g In. The T e c t o n i c H i s t o r y Of W e s t e r n Canada , A P l a t e T e c t o n i c M odel . 19 2.4 A n a l y s i s Of C o n d i t i o n s N e c e s s a r y F o r F a u l t R e a c t i v a t i o n A t The S u l l i v a n 25 CHAPTER 3: The 1980 S u l l i v a n Mine S e i s m i c P r o j e c t 32 3.1 O b j e c t i v e s '. — . 32 3.2 The F i e l d E x p e r i m e n t .. 33 3.3 A r r a y I n s t a l l a t i o n And M a i n t e n a n c e .36 3.4 I n s t r u m e n t a t i o n 37 3.5 D a t a E d i t i n g ... '41 3.6 E r r o r s In E v e n t A r r i v a l Time Measurements 44 3.7 I n s t r u m e n t P o l a r i t i e s 45 CHAPTER 4: V e l o c i t y M o d e l F o r The S u l l i v a n Mine A r e a 4'6 V 4.1 Development Of A U n i f o r m Model 46 4.2 J u s t i f i c a t i o n F o r A U n i f o r m V e l o c i t y M o d e l : D i s c u s s i o n Of D e v i a t i o n s Due To G e o l o g i c S t r u c t u r e .. 52 4.3 The S t a t i o n W e i g h t i n g F a c t o r 57 4.4 E f f e c t Of The Mine W o r k i n g s On The Model 58. CHAPTER 5: D a t a S e t C h a r a c t e r i t i c s 59 5.1 E v e n t C l a s s i f i c a t i o n : 59 5.2 E x p l o s i o n - M i c r o e a r t h g u a k e D i s c r i m i n a t i o n P r o b l e m s ... 69 5.3 H y p o c e n t r e L o c a t i o n 74 5.4 N o n - L o c a t a b l e E v e n t s 76 5.5 I m p o r t a n c e Of C o n s t r a i n i n g C a l c u l a t e d H y p o c e n t r e s .. 76 5.6 H y p o c e n t r a l A c c u r a c y Based On E x p l o s i o n s 79 5.7 The E f f e c t Of Changes In The V e l o c i t y M o d e l ......... 85 CHAPTER 6: A n a l y s i s And I n t e r p r e t a t i o n . 90 6.1 E v e n t L o c a t i o n , An O v e r a l l P i c t u r e 90 6.2 The Emergent E v e n t s 93 6.3 E v e n t s W i t h i n The Mine A r e a , A D e t a i l e d P i c t u r e .... 96 6.4 E v e n t O r i g i n Time A n a l y s i s 106 CHAPTER 7: C o n c l u s i o n s , S p e c u l a t i o n s And Summary 117 7.1 F u t u r e Programs 122 REFERENCES 125 APPENDIX 1: C l o c k D r i f t E r r o r s , 130 APPENDIX 2: H y p o c e n t r e L o c a t i o n 133 v i L I S T OF T A B L E S 3 . 1 S e i s m o g r a p h L o c a t i o n s I n T e r m s Of The M i n e C o o r d i n a t e S y s t e m 34 4 . 1 D e p a r t u r e Of The P - w a v e A r r i v a l T i m e A t E a c h S t a t i o n F r o m The U n i f o r m V e l o c i t y C u r v e F o r E a c h T e s t E v e n t . . . . . 54 5 . 1 D i f f e r e n c e s B e t w e e n The C a l c u l a t e d E x p l o s i o n H y p o c e n t r e s A n d T h e i r T r u e P o s i t i o n s , F o r V e l o c i t i e s R a n g i n g F r o m 5 . 1 To 5 . 5 K m s " 1 83 v i i L I S T OF FIGURES 1.1 L o c a t i o n Of The S u l l i v a n Mine, K i m b e r l e y , B.C. 9 1.2 L o c a t i o n Of The S u l l i v a n Orebody I n R e l a t i o n To M a j o r F a u l t S u r f a c e T r a c e s In The R e g i o n 10 1.3 Geometry Of The S u l l i v a n Orebody 11 .2.1 F a u l t s W i t h i n The S u l l i v a n Mine, F o o t w a l l T r a c e .......... 17 2.2 S c h e m a t i c E v o l u t i o n Of The C a n a d i a n C o r d i l l e r a , 1500 To 230 Ma 21 2.3 S c h e m a t i c E v o l u t i o n Of The C a n a d i a n C o r d i l l e r a , 230 To 95 Ma 22 2.4 Mechanisms F o r F a u l t R e a c t i v a t i o n In The Mine E n v i r o n m e n t • • 25 2.5 S c h e m a t i c R e d i s t r i b u t i o n Of The .Overburden L o a d In An U n d e r g r o u n d Mine 28 2.6 R e g i o n a l S t r e s s C o n f i g u r a t i o n s N e c e s s a r y To A l l o w F a u l t R e a c t i v a t i o n Due To U n l o a d i n g 29 3.1 V e l o c i t y S e n s i t i v i t y Of U.B.C S e i s m o g r a p h S y s t e m s 38 3.2 C l o c k D r i f t C u r v e F o r D i g i t a l U n i t 008 At PMP 40 3.3 T y p i c a l E v e n t R e c o r d e d By 7 D i g i t a l And 3 A n a l o g S t a t i o n s . .. 43 4.1 T r a v e l - T i m e D i a g r a m F o r The June 20, 1980 Open P i t B l a s t 47 4.2 T r a v e l - T i m e D i a g r a m "For The J u l y 3, 1980 Open P i t B l a s t 48 4.3 T r a v e l - T i m e D i a g r a m F o r The J u l y 8, 1980 #10 P i t B l a s t s 49 4.4 L o c a t i o n Of The C a l i b r a t i o n E v e n t s , T1, T2, T3 & T4, v i i i And T h e i r C a l c u l a t e d E p i c e n t r e s 56 5.1 E v e n t C l a s s i f i c a t i o n 60 5.2 Example Of An Emergent E v e n t . . . - 61 5.3 Example Of A M u l t i p l e B l a s t 63 5.4 Example Of An E x p l o s i o n E v e n t 64 5.5 Example Of An E v e n t O u t s i d e Our R e g i o n Of I n t e r e s t .... 66 5.6 Example Of A T y p i c a l Weekend E v e n t 68 5.7 S t a t i o n E l e v a t i o n And R a d i a l D i s t a n c e W i t h R e s p e c t To The Open P i t B l a s t s .. 72 5.8 E v e n t E p i c e n t r e s C a l c u l a t e d W i t h o u t MRK 77 5.9 E v e n t E p i c e n t r e s C a l c u l a t e d I n c l u d i n g MRK 78 5.10 C a l c u l a t e d E x p l o s i o n E p i c e n t r e s 80 5.11 C a l c u l a t e d E x p l o s i o n H y p o c e n t r e s P r o j e c t e d Onto A N o r t h - S o u t h Mine C r o s s S e c t i o n . . . 81 5.12 C a l c u l a t e d E x p l o s i o n H y p o c e n t r e s P r o j e c t e d Onto An E a s t - W e s t Mine C r o s s S e c t i o n 82 5.13 E f f e c t Of V e l o c i t y Changes On E p i c e n t r a l L o c a t i o n ...... 86 5.14 E f f e c t Of V e l o c i t y Changes On H y p o c e n t r a l L o c a t i o n , N o r t h - S o u t h C r o s s S e c t i o n 87 5.15 E f f e c t Of V e l o c i t y Changes On H y p o c e n t r a l L o c a t i o n , E a s t - W e s t C r o s s S e c t i o n 88 6.1 E p i c e n t r a l Map Of A l l E v e n t s L o c a t e d A t The S u l l i v a n M i n e , June - J u l y , 1980 91 6.2 T h r e e D i m e n s i o n a l R e p r e s e n t a t i o n Of A l l E v e n t H y p o c e n t r e s At The S u l l i v a n Mine : 92 6.3 E p i c e n t r e s Of Emergent E v e n t s A t The S u l l i v a n Mine .... 94 6.4 H i s t o g r a m , Number Of Emergent E v e n t s Per Day 95 6.5 E v e n t H y p o c e n t r e s P r o j e c t e d O nto A N o r t h - S o u t h C r o s s i x S e c t i o n . . . 97 6.6 E v e n t H y p o c e n t r e s P r o j e c t e d Onto An E a s t - W e s t C r o s s S e c t i o n 98 6.7 E v e n t E p i c e n t r e s In The Mine A r e a . .. 102 6.8 F a u l t s In The Mine A r e a 101 6.9 A c t i v e B l o c k s , J u n e - J u l y , 1980 100 6.10 Cave A r e a s Above The S u l l i v a n Mine 105 6.11 E v e n t E p i c e n t r e s In The Mine A r e a 104 6.12 E p i c e n t r a l L o c a t i o n s Of The Weekend E v e n t s 107 6.13 H i s t o g r a m , Number Of E v e n t s P e r Day ' — . 109 6.14 H i s t o g r a m , Number Of E v e n t s Per 8 Hour S h i f t P e r i o d .. 110 6.15 H i s t o g r a m , Number Of E v e n t s Per Hour 112 6.16 H i s t o g r a m , Number Of E v e n t s Per 10 M i n u t e P e r i o d D u r i n g The J u l y 9, 1980 A f t e r n o o n S h i f t B l a s t 113 6.17 H i s t o g r a m , Number Of E v e n t s Per Hour F o l l o w i n g The J u l y 11, 1980 T h r e e S t a g e P i l l a r B l a s t 114 6.18 H i s t o g r a m , Number Of E v e n t s Per Hour F o r The Weekends Commencing 10:30 Pm On June 20, June 27 And J u l y 4, 1980 116 7.1 R e l a t i o n s h i p Between E v e n t E p i c e n t r e s , Cave A r e a s And F a u l t s 119 X ACKNOWLEDGEMENTS I t seems t h a t t h e a c k n o w l e d g e m e n t s a r e so many and v a r i e d t h a t i t w i l l r e a d more l i k e a l i s t o f movie c r e d i t s a t t h e H o l l y w o o d Cinema. Shot on l o c a t i o n a t t h e S u l l i v a n Mine under t h e d i r e c t i o n o f Cominco L i m i t e d , we have i n o r d e r o f a p p e a r a n c e : S u p e r v i s o r Bob E l l i s F i e l d w o r k Bob Meldrum, Bob E l l i s , Lynne B l e w e t t A s s i s t a n c e w i t h U n d e r g r o u n d S t a t i o n s Howard H o l l a n d s , G e o r g e Wanuck T e s t E x p l o s i o n s i n # 1 0 P i t B i l l R u s s e l l S u r v e y i n g o f S t a t i o n L o c a t i o n s Lynne B l e w e t t , A r t B u r r o w s Programming and D a t a P r o c e s s i n g Bob Meldrum, Ken W h i t t a l l , K e r r y S t i n s o n , B i l l S l a w s o n P e r s o n a l C o m m u n i c a t i o n s P a u l Ransom, John H a m i l t o n , Ken M c C l a y , Howie P e a r s o n W r i t i n g A s s i s t a n c e and Comments Bob E l l i s , Bob Meldrum, P a u l Ransom, J o h n H a m i l t o n T y p i n g on U.B.C. Computer and FMT Susan C l e g g , Ed W a d d i n g t o n E x t r a s p e c i a l t h a n k s must go t o t h e f o l l o w i n g p e o p l e : Bob Meldrum f o r b o t h h i s company and t e c h n i c a l s u p p o r t d u r i n g t h e many l o n g h o u r s s p e n t i n t h e f i e l d and i n t h e l a b ; Lynne B l e w e t t f o r h e r a s s i s t a n c e and company i n t h e f i e l d ; P a u l Ransom f o r h i s e f f o r t i n p r o v i d i n g maps, i n f o r m a t i o n and comments d u r i n g t h e d a t a a n a l y s i s s t a g e ; Susan C l e g g f o r p e r s e v e r i n g w i t h t h e t y p i n g a s w e l l as p r o v i d i n g " G e o p h y s i c s House" w i t h t h e o c c a s i o n a l d i n n e r and f i n a l l y Bob E l l i s f o r h i s s k i l l f u l l , a l l s e e i n g eye x i i n g u i d i n g t h e t h e s i s i n t o i t s f i n a l f o r m . Thanks a l s o t o Ian and Gemma J o n e s and S t e v e and S h e l l e y P e a r c e f o r t h e i r h o s p i t a l i t y i n t h e f i n a l month o f my t h e s i s f o l l o w i n g t h e d o w n f a l l of " G e o p h y s i c s House". P r i n c i p a l f i n a n c i a l s u p p o r t was p r o v i d e d by Cominco L i m i t e d w i t h s u b s i d i a r y s u p p o r t from t h e U.B.C. N a t u r a l , A p p l i e d and H e a l t h S c i e n c e s G r a n t Committee and t h e N a t u r a l S c i e n c e s and E n g i n e e r i n g R e s e a r c h C o u n c i l of Canada. 1 CHAPTER 1 1.1 INTRODUCTION E a r t h q u a k e a c t i v i t y o c c u r s i n r e s p o n s e t o c h a n g i n g s t r e s s c o n d i t i o n s i n t h e e a r t h ' s b r i t t l e l i t h o s p h e r e . One c l a s s o f e a r t h q u a k e s a r e t h o s e i n d u c e d by t h e a c t i v i t i e s of man. S e v e r a l t y p e s o f human a c t i v i t y have r e s u l t e d i n t h e s t i m u l a t i o n of e a r t h q u a k e s , some as l a r g e as m a g n i t u d e 6.5 (Simpson, 1976). T h e s e a c t i v i t i e s have been w e l l documented r e c e n t l y i n s e v e r a l m a j o r s y m p o s i a ( M i l n e , 1976; H a r d y and L e i g h t o n , 1977) The a c t i v i t i e s a r e as f o l l o w s : ( i ) D e t o n a t i o n of l a r g e u n d e r g r o u n d e x p l o s i o n s : K i s s l i n g e r (1976) d i s c u s s e s s e i s m i c a c t i v i t y f o l l o w i n g e x p l o s i o n s s u c h as t h o s e d e t o n a t e d a t t h e Nevada T e s t S i t e by t h e U.S. A t o m i c E n e r g y C o m m i s s i o n . The l a r g e number o f s m a l l e a r t h q u a k e s t h a t b e g i n a f t e r d e t o n a t i o n and c o n t i n u e f o r s e v e r a l weeks a r e a t t r i b u t e d t o c o l l a p s e o f t h e e x p l o s i o n - c r e a t e d c a v i t y ( K i s s l i n g e r , 1976). O b s e r v a b l e d i s p l a c e m e n t s on n e a r b y f a u l t s a r e r e p o r t e d i n o n l y a few c a s e s . K i s s l i n g e r (1976) s t a t e s t h a t e a r t h q u a k e s , o t h e r t h a n t h o s e a s s o c i a t e d w i t h t h e c a v i t y , w i l l o c c u r o n l y i f t h e medium i s a l r e a d y h i g h l y s t r e s s e d . I n s u c h a c a s e t h e e x p l o s i o n s e r v e s t o d e c r e a s e t h e e f f e c t i v e p r i n c i p a l s t r e s s e s e i t h e r by m o m e n t a r i l y i n c r e a s i n g t h e p o r e f l u i d p r e s s u r e o r by c r e a t i n g a t r a n s i e n t t e n s i l e s t r e s s t h a t r e d u c e s 2 t h e n o r m a l s t r e s s on t h e f a u l t p l a n e , t h u s a l l o w i n g s l i p t o o c c u r i n r e s p o n s e t o t h e p r e - e x i s t i n g s t r e s s . ( i i ) F l u i d I n j e c t i o n : T e c t o n i c movements have been i n d u c e d a t a number of s i t e s where f l u i d i n j e c t i o n i s t a k i n g p l a c e t h r o u g h . b o r e h o l e s , s u c h as t h e Rocky M o u n t a i n A r s e n a l w e l l n e a r D e n v e r , C o l o r a d o . In t h i s c a s e waste f l u i d s were b e i n g i n j e c t e d i n t o t h e s u b s u r f a c e f o r m a t i o n s a t f l o w r a t e s of m i l l i o n s o f g a l l o n s p e r month and a t p r e s s u r e s up t o 1000 p s i (7 x 10 6 Nm"2) g r e a t e r t h a n t h e o r i g i n a l f o r m a t i o n p o r e p r e s s u r e ( K i s s l i n g e r , 1976). E a r t h q u a k e s may o c c u r when i n j e c t i o n i s c a r r i e d out i n a r e a s w i t h a p r e - e x i s t i n g t e c t o n i c s t r e s s . I n c r e a s e d p o r e p r e s s u r e w i l l r e d u c e t h e e f f e c t i v e p r i n c i p a l s t r e s s e s t h u s a l l o w i n g p r e - s t r e s s e d f a u l t p l a n e s i n t h e r e g i o n t o become u n l o c k e d . ( i i i ) R e s e r v o i r Impoundment: E a r t h q u a k e s a r e r e c o r d e d d u r i n g i n i t i a l f i l l i n g o f a p p r o x i m a t e l y 10% of a l l l a r g e r e s e r v o i r s (dam h e i g h t ^ 100 m, volume > 1.23 x 10 9 m 3) and s u b s e q u e n t a c t i v i t y may o c c u r d u r i n g s e a s o n a l c h a n g e s i n water l e v e l (Simpson, 1976). I t i s g e n e r a l l y f e l t t h a t t h e r e must be a p r e - e x i s t i n g t e c t o n i c s t r e s s c l o s e t o t h e f a i l u r e s t r e n g t h o f t h e f a u l t s (Gough and Gough, 1970). T h i s i s c l e a r l y t h e c a s e when we see m a g n i t u d e 6 e a r t h q u a k e s i n d u c e d when t h e added water p r e s s u r e i s no more t h a n 10-15 b a r s ( K i s s l i n g e r , 1976). C o n s e n s u s now i s i n f a v o u r o f t h i s a c t i v i t y b e i n g p r i n c i p a l l y due t o c h a n g e s i n t h e p o r e 3 water p r e s s u r e w i t h t h e i n c r e a s e d s u r f a c e l o a d i t s e l f o n l y p l a y i n g a m i n o r r o l e (Snow, 1973). K i s s l i n g e r (1976) b e l i e v e s t h a t t h e e f f e c t o f s t r e s s c o r r o s i o n i n s i l i c a t e r o c k s may a l s o p l a y a r o l e i n w e a k e n i n g t h e medium. ( i v ) M i n i n g and Q u a r r y i n g : M i n i n g g i v e s r i s e t o s e i s m i c a c t i v i t y r a n g i n g from m i c r o s e i s m i c e v e n t s o f m a g n i t u d e -6 t o r a r e e v e n t s o f m a g n i t u d e 5 (Cook, 1976). Rock f a i l u r e s i n t h e mine e n v i r o n m e n t may be c l a s s i f i e d i n t o t h r e e m a j o r c a t e g o r i e s ( m o d i f i e d f r o m Cook, 1976). (a) R o c k f a l l s - l o o s e n e d r o c k f a l l s under i t s own w e i g h t , commonly c a l l e d r o o f o r h a n g i n g w a l l c o l l a p s e . When t h i s o c c u r s an a s s o c i a t e d a i r b l a s t i s g e n e r a l l y f e l t t h r o u g h o u t t h e i n t e r c o n n e c t e d mine t u n n e l s . (b) R o c k b u r s t s - v i o l e n t f a i l u r e s of r o c k t h a t t e n d t o o c c u r when t h e r o c k i s u n u s u a l l y s t r o n g o r u n f r a c t u r e d and t h u s c a p a b l e of s t o r i n g l a r g e amounts o f s t r a i n e n e r g y . T h e s e f a i l u r e s may c a u s e e x t e n s i v e damage t o t h e mine w o r k i n g s and a l s o have an a s s o c i a t e d a i r b l a s t . ( c ) O u t b u r s t s - more t y p i c a l t o c o a l m i n e s ; o c c u r when t h e r a p i d r e l e a s e o f gas c a u s e s r o c k t o be e j e c t e d i n t o t h e e x c a v a t i o n . D u r i n g u n d e r g r o u n d m i n i n g , l o c a l a r e a s o f h i g h s t r e s s d e v e l o p as t h e o v e r b u r d e n l o a d i s u n l o a d e d from a p a r t i c u l a r a r e a ( s t o p e ) and r e d i s t r i b u t e d o n t o t h e n e a r b y p i l l a r s and s u r r o u n d i n g w a l l s . The a r e a s of h i g h e s t s t r e s s a r e t h u s i n t h e v i c i n i t y o f t h e a d v a n c i n g mine f a c e s , and i t i s i n t h i s r e g i o n •4 t h a t m i c r o e a r t h q u a k . e s due t o r o c k f r a c t u r e w i l l o c c u r i n o r d e r t o r e l i e v e t h o s e s t r e s s e s (McGarr e t a l , 1975). In t h i s s t u d y we a r e i n t e r e s t e d i n a f o u r t h and s m a l l e r c a t e g o r y of m i n i n g i n d u c e d m i c r o e a r t h q u a k e s w h i c h o c c u r a t some d i s t a n c e f r o m t h e mine f a c e s a l o n g p l a n e s of weakness, s u c h a s f a u l t s , j o i n t s , b e d d i n g and f o l i a t i o n p l a n e s , e x i s t i n g i n t h e r o c k . 1.2 SELECTED PREVIOUS STUDIES OF MINING INDUCED SEISMICITY (a) E a s t Rand P r o p r i e t a r y M i n e , S o u t h A f r i c a A t t h e E a s t Rand P r o p r i e t a r y Mine i n t h e W i t w a t e r s r a n d , some of t h e o r e r e m o v a l i s t a k i n g p l a c e a t 3.2 km d e p t h , w h i c h c o r r e s p o n d s t o a c o n f i n i n g p r e s s u r e of 860 b a r s (McGarr e t a l , 1975). S e i s m i c a c t i v i t y i s g e n e r a l l y c o n f i n e d t o a r e g i o n between 100 m i n a d v a n c e o f t h e mine f a c e and 30 m b e h i n d i t a l t h o u g h o c c a s i o n a l e v e n t s do o c c u r f u r t h e r from t h e mine f a c e and a r e p o s s i b l y a s s o c i a t e d w i t h f a u l t s (N.G.W. Cook, p e r s o n a l c o m m u n i c a t i o n ) . Most o f t h e e v e n t s a r e o b s e r v e d t o o c c u r d u r i n g and i n t h e f i r s t few h o u r s i m m e d i a t e l y a f t e r b l a s t i n g . The g e n e r a l l e v e l of s e i s m i c a c t i v i t y i s h i g h e x c e p t on Sundays when no m i n i n g t a k e s p l a c e . M cGarr e t a l (1975) f o u n d t h a t t h e t o t a l c a l c u l a t e d s t r e s s f i e l d o n l y e x c e e d e d t h e f a i l u r e s t r e n g t h f o r q u a r t z i t e w i t h i n a v e r y s m a l l r e g i o n , a p p r o x i m a t e l y 10 m r a d i u s , a b o u t t h e mine f a c e w h i c h o n l y a c c o u n t s f o r a s m a l l number o f t h e t o t a l o b s e r v e d s e i s m i c e v e n t s . McGarr (1971a) o b s e r v e d f a i l u r e i n 5 t h i s r e g i o n a s two s e t s of e n - e c h e l o n f r a c t u r e s y s t e m s t h a t d e v e l o p a b o u t 10 m i n a d v a n c e o f t h e m i n i n g f a c e and t o some e x t e n t d e - s t r e s s t h e r o c k . T h e s e a r e u s u a l l y " n o n - v i o l e n t " f a i l u r e s b u t may o c c u r a s e x p l o s i v e " b u r s t s " i f t h e r o c k i s u n u s u a l l y s t r o n g o r u n f r a c t u r e d and t h u s c a p a b l e of s t o r i n g l a r g e r amounts o f s t r a i n e n e r g y b e f o r e g i v i n g way. McGarr e t a l (1975) s u g g e s t t h a t t h e r e m a i n d e r of t h e e v e n t s , t h o s e more t h a n 10-15 m away from t h e m i n i n g f a c e , a r e t h e r e s u l t o f d i f f e r e n t i a l s t r e s s e s due t o m i n i n g t r i g g e r i n g t h e r e l e a s e o f s t o r e d s t r a i n e n e r g y . S t r a i n - r e l i e f measurements i n b o r e h o l e s i n d i c a t e t h a t t h e r e a r e r e g i o n s o f " l o c k e d i i i " r e s i d u a l s t r e s s i n t h e W i t w a t e r s r a n d q u a r t z i t e s 600 t o 700 b a r s l a r g e r t h a n t h e amb i e n t v i r g i n s t r e s s . M c G arr e t a l (1975) u s e d a 3 - d i m e n s i o n a l , ten. s t a t i o n a r r a y c o n c e n t r a t e d a b o u t t h e a d v a n c i n g mine f a c e , w i t h t h e f u r t h e s t geophone a b o u t 2 km away. The s y s t e m f r e q u e n c y r e s p o n s e was from 15 t o 200 Hz and t i m i n g was on a common b a s e , t h u s a l l o w i n g an a r r i v a l t i m e a c c u r a c y of 0.001 t o 0.002 s. A P-wave v e l o c i t y o f 5.8 t o 6.1 kms" 1 was d e t e r m i n e d f r o m c a l i b r a t i o n b l a s t s w h i c h were a l s o u s e d t o d e t e r m i n e t h a t a l o c a t i o n a c c u r a c y of 20 m i n p l a n and 30 m i n d e p t h was p o s s i b l e . E v e n t l o c a t i o n s were c a l c u l a t e d u s i n g a 3 - d i m e n s i o n a l l e a s t s q u a r e s a p p r o a c h . (b) S u n n y s i d e C o a l M i n i n g D i s t r i c t o f U t a h I n a s e i s m i c s t u d y o f an a r e a o f t h e Geneva c o a l mine, w h i c h i s under 100 m o f o v e r b u r d e n , S m i t h e t a l (1974) f o u n d t h e p r i n c i p a l c o n c e n t r a t i o n o f f o c a l d e p t h s t o be 0.5 t o 1.5 km b e n e a t h a p o r t i o n o f t h e a c t i v e m i n i n g a r e a w h i c h e x h i b i t e d 6 f l o o r and r o o f f a i l u r e s . The c o m p o s i t e f a u l t p l a n e s o l u t i o n i n d i c a t e d a t h r u s t f a u l t i n g mechanism, and as t h e s o l u t i o n n e a r l y p a r a l l e l s t h e d i p of t h e f o o t w a l l s h a l e s , b e d d i n g p l a n e f a i l u r e was s u g g e s t e d . A d i s t i n c t c o r r e l a t i o n was o b s e r v e d between t h e number of e v e n t s a t t h i s s i t e and t h e w e e k l y w o r k i n g c y c l e . S m i t h e t a l (1974) n o t e t h a t t h e s o l u t i o n i s i n g e n e r a l agreement w i t h t h e r e g i o n a l s t r e s s p a t t e r n c r e a t e d by t h e t e c t o n i c d e v e l o p m e n t o f t h e n e a r b y San R a f a e l S w e l l . They s u g g e s t t h a t t h e main e a r t h q u a k e e n e r g y i s from r e g i o n a l t e c t o n i c s t r e s s . S m i t h e t a l (1974) u s e d a 6 s t a t i o n s u r f a c e a r r a y , d e p l o y e d i n a 10 km by 10 km a r e a . T h r e e o f t h e s t a t i o n s had WWVB r a d i o t i m e and t h e r e m a i n d e r had c r y s t a l c l o c k s . The t o t a l a r r i v a l t i m e e r r o r was e s t i m a t e d t o be i n t h e r a n g e f r o m 0.02 s t o 0.1 s. E v e n t l o c a t i o n was done u s i n g a two d i m e n s i o n a l p r o g r a m c a p a b l e o f t a k i n g i n t o a c c o u n t s t a t i o n e l e v a t i o n s and d i f f e r e n t s u r f a c e v e l o c i t y m o d e l s . A t h r e e l a y e r e d v e l o c i t y model was u s e d , b a s e d on g e o l o g i c s e c t i o n s o f t h e a r e a . ( c ) D o l o m i t e Q u a r r y , W a p p i n g e r s F a l l s , New York S t a t e F o l l o w i n g a m a g n i t u d e 3.3 e a r t h q u a k e a t W a p p i n g e r s F a l l s , Pomeroy e t a l (1976) f o u n d t h e f o c a l d e p t h s o f t h e a f t e r s h o c k s t o be a t 0.5 t o 1.2 km below a m a j o r d o l o m i t e q u a r r y i n t h e r e g i o n . The c o m p o s i t e f a u l t p l a n e s o l u t i o n f o r t h e main shock and t h e w e l l l o c a t e d a f t e r s h o c k s i n d i c a t e s a t h r u s t mechanism w h i c h s u p p o r t s t h e p r e s e n c e of a n o r t h - n o r t h e a s t t r e n d i n g maximum c o m p r e s s i v e s t r e s s i n e a s t e r n N o r t h A m e r i c a . They b e l i e v e t h a t 7 t h e e a r t h q u a k e s e q u e n c e , and p o s s i b l y p a s t e a r t h q u a k e s i n t h e a r e a , may have been t r i g g e r e d by c r u s t a l u n l o a d i n g due t o q u a r r y i n g , i n t h e p r e s e n c e of h i g h h o r i z o n t a l c o m p r e s s i v e s t r e s s . Pomeroy e t a l (1976) u s e d a s u r f a c e a r r a y o f f i v e S p r e n g n e t h e r MEQ-800 drum r e c o r d i n g s e i s m o g r a p h s i n a 5 km by 6 km a r e a a b o u t t h e q u a r r y . T i m i n g was done by c r y s t a l c l o c k s t h a t were c a l i b r a t e d o nce p e r d a y . A t i m i n g a c c u r a c y o f ± 0.020 s was e s t i m a t e d f o r i m p u l s i v e a r r i v a l s . H y p o c e n t r a l l o c a t i o n s were o b t a i n e d u s i n g a two d i m e n s i o n a l p r o g r a m , a m o d i f i e d v e r s i o n o f HYP071 (Lee and L a h r , 1972). A u n i f o r m v e l o c i t y model was u s e d , d e t e r m i n e d by u s i n g t h e v a l u e f o r d o l o m i t e from t a b l e s . In t h e l a t t e r two s t u d i e s d i s c u s s e d a b o v e , s o u r c e mechanisms were c o n s i s t e n t w i t h t h r u s t f a u l t i n g i n t h e r e g i o n ; however t h e l o c a t i o n s were n o t a t t r i b u t a b l e t o any s p e c i f i c f a u l t s . T h i s v o l u m e t r i c d i s t r i b u t i o n o f t h e f o c i may however be due, a t l e a s t i n p a r t , t o l i m i t a t i o n s i n t h e e x p e r i m e n t a l d e s i g n . In p a r t i c u l a r , l i m i t a t i o n s o f t h e t w o - d i m e n s i o n a l a r r a y g e o m e t r y u s e d , as w i l l be d i s c u s s e d l a t e r , s h e d s d o u b t on t h e c a l c u l a t e d f o c a l d e p t h s . I f t h e s e t y p e of i n d u c e d m i c r o e a r t h q u a k e s c a n be l o c a t e d w i t h s u f f i c i e n t a c c u r a c y , say w i t h i n 100 m, t h e n t h e i r l o c a t i o n w ould p r o v i d e a v a l u a b l e a i d t o g e o l o g i c a l i n t e r p r e t a t i o n i n t h e mine e n v i r o n m e n t . The l o c a t i o n , d i p and c u r v a t u r e o f p l a n e s o f weakness s u c h as f a u l t s , s h e a r s and f r a c t u r e s , p r e - e x i s t e n t i n t h e mine r e g i o n and c o n s e q u e n t l y r e a c t i v a t e d by o r e r e m o v a l would be c l e a r l y d e l i n e a t e d by z o n e s of c o n c e n t r a t e d s e i s m i c 8 a c t i v i t y . 1.3 INTRODUCTION TO THE 1980 SULLIVAN MINE PROJECT The b a s i c o b j e c t i v e of t h e 1980 S u l l i v a n Mine p r o j e c t i s t o d e t e r m i n e whether or n o t i t i s f e a s i b l e . t o d e l i n e a t e f a u l t p l a n e s u s i n g m i n i n g i n d u c e d e a r t h q u a k e s and any n a t u r a l e v e n t s i n t h e mine a r e a . The f i e l d e x p e r i m e n t was c a r r i e d o u t a t t h e S u l l i v a n Mine w h i c h i s l o c a t e d n e a r K i m b e r l e y , B r i t i s h C o l u m b i a ( F i g u r e 1.1). The S u l l i v a n o r e b o d y , o u t l i n e d i n F i g u r e 1.2, i s one o f t h e w o r l d ' s g r e a t e s t s t r a t i f o r m l e a d - z i n c s u l p h i d e d e p o s i t s w i t h an a r e a l e x t e n t o f 3 km 2 and a t h i c k n e s s r a n g i n g from a b o u t 30 t o 90 m. The o r e b o d y i s s u r r o u n d e d by major f a u l t s a n d c u t by numerous s m a l l e r f a u l t s . F i g u r e 1.2 shows t h e f o u r m a j o r f a u l t s - b o r d e r i n g .the o r e l e n s ; t h e y a r e t h e K i m b e r l e y , S u l l i v a n , H i d d e n Hand and L o i s C r e e k f a u l t s . In t h r e e d i m e n s i o n s t h e o r e body has t h e shape of an i n v e r t e d s a u c e r d i p p i n g t o t h e n o r t h - e a s t ( F i g u r e 1.3). The t y p e o f m i n i n g a c t i v i t y t a k i n g p l a c e a t t h e S u l l i v a n i s d e s c r i b e d by P. Ransom ( p e r s o n a l c o m m u n i c a t i o n , 1 9 8 2 ) : ) L i ) P r i m a r y b l a s t i n g - t h e i n i t i a l p i l l a r b l a s t i n v o l v i n g some t o n n e s o f e x p l o s i v e . T h e r e i s o n l y one b l a s t of t h i s t y p e p e r b l o c k . i i ) S e c o n d a r y b l a s t i n g - done w h i l e a b l o c k i s p r o d u c i n g , g e n e r a l l y d u r i n g t h e l a s t h a l f o f t h e b l o c k ' s p r o d u c t i o n l i f e . One o r s e v e r a l d r a w p o i n t s a r e b l a s t e d a t a t i m e , g e n e r a l l y i n v o l - v i n g 10' t o 50 pounds o f e x p l o s i v e p e r d r a w p o i n t . The o b j e c t i v e i s t o b r e a k up l a r g e c h u n k s o f r o c k b l o c k i n g t h e 6 f t by 6 f t o p e n i n g s . 9 : v • : •-" 1 Vt=: PACIFIC O C E A N \ ^ g g p ^ ^ trz.-^-z_-TL.-r_-i.-* 1 / C-Z-I-I-3 *3 C A N A D A \\ \ ^ VANCOUVER I • • "v' SUL SEATTLE /4*i->-->>i>^t LIVAN MINE MBERLEY B.C. A* U.S.A Rocky Mountain Belt Omineca Crystalline Belt Intermontane Belt Coast Plutonic Complex Insular Belt o k i l o m e t r e s 500 F i g u r e 1.1 L o c a t i o n o f t h e S u l l i v a n M i n e , K i m b e r l e y , B r i t i s h C o l u m b i a . K i m b e r l e y i s s i t u a t e d i n t h e Rocky M o u n t a i n B e l t o f t h e C a n a d i a n C o r d i l l e r a ( a d a p t e d f r o m Monger and P r i c e , 1979). o o a o a + BOG # SUL / A MRK 49'42.5'N 1 000 m MAT •1B0Q0 1 -] 2000 , * PMP w* « ) / > / .OREBODY / ' I I f / ^ * 039 •.SHF ^ ^ • ~ P 1 T + NRD ^ LOI *° / ~ 2~Jt HIDDEN^HAND S - NCN R * MOR <0 > 1 1 6 0 0 W -6000 000 6000 ! 2000 F i g u r e 1 . 2 L o c a t i o n of the S u l l i v a n Orebody i n r e l a t i o n t o the Surface Traces of Major F a u l t s i n the Region. -The U.B.C. seismograph network i s a l s o shown w i t h the s t a t i o n l o c a t i o n s i n d i c a t e d as diamonds, each w i t h a standard three l e t t e r t i t l e . For convenience the axes on t h i s , and a l l subsequent diagrams w i l l use the mine c o o r d i n a t e system i n f e e t . GEOMETRY OF THE SULLIVAN OREBODY MINE COORDINATES ( FEET ) F i g u r e 1.3 Geometry o f t h e S u l l i v a n O r e b o d y . The o r e b o d y i s r e p r e s e n t e d a s a s u r f a c e p r o j e c t i o n a n d two c r o s s s e c t i o n s , one n o r t h - s o u t h and t h e o t h e r e a s t -w est. S e i s m i c s t a t i o n s D39 and D27 a r e l o c a t e d w i t h i n t h e u n d e r g r o u n d w o r k i n g s . 1 2 i i i ) D e v e lopment b l a s t i n g - i n v o l v e s p r e p a r a t i o n of ramps and d r i f t s p r i o r t o o r e e x t r a c t i o n b l a s t i n g . i v ) C h u t e b l a s t i n g - i f c h u t e s become b l o c k e d and t r a i n s c a n n o t be l o a d e d , t h e hangups have t o be b l a s t e d down. About 10 pounds of e x p l o s i v e s m i g h t be u s e d i n s u c h c a s e s . E x p l o s i o n s of t h e above n a t u r e w i l l be c o n f i n e d t o w e l l - d e f i n e d p r o d u c i n g a r e a s . 1.4 PREVIOUS STUDIES AT THE SULLIVAN MINE Two p r e v i o u s s t u d i e s c o n d u c t e d a t t h e S u l l i v a n Mine i n d i c a t e d t h a t t h e r e were s u f f i c i e n t l o c a t a b l e m i c r o e a r t h q u a k e e v e n t s t o w a r r a n t a f u r t h e r 1 t o 2 month r e c o r d i n g p r o g ram t o examine t h e p o s s i b i l i t y o f f a u l t d e l i n e a t i o n by t h i s means. (a) S e n t u r i o n S c i e n c e s S t u d y In 1971, Cominco L i m i t e d engaged S e n t u r i o n S c i e n c e s I n c o r p o r a t e d t o c a r r y o u t two b r i e f m i c r o e a r t h q u a k e s t u d i e s n e a r K i m b e r l e y , B.C. w i t h one t e s t a r e a c e n t e r e d on t h e S u l l i v a n Mine and a n o t h e r on a w i d e r a r e a of t h e Rocky M o u n t a i n T r e n c h ( S e n t u r i o n S c i e n c e s I n c , 1971). In t h e S u l l i v a n p r o g r a m a 4 s e i s m o g r a p h s u r f a c e a r r a y of a p p r o x i m a t e l y 5 km by 5 km was o p e r a t e d f o r 8 1/2 d a y s . D u r i n g t h i s p e r i o d , a p i l l a r b l a s t was r e c o r d e d and a l t h o u g h d e t a i l s a r e n o t p r o v i d e d , t h e r e p o r t i m p l i e s t h a t t h e o r i g i n t i m e of t h e b l a s t was known as w e l l a s t h e s h o t c o o r d i n a t e s . C o m p r e s s i o n a l wave v e l o c i t i e s r a n g e d from 5.03 kms" 1 t o 5.89 kms" 1 w i t h a mean of 5.41 kms' 1. V e l o c i t i e s i n t h e i r h y p o c e n t r e p r o g r a m were t h e n v a r i e d and t h e minimum d e v i a t i o n o f t h e computed h y p o c e n t r e f r o m t h e b l a s t l o c a t i o n was 1 3 f o u n d f o r a v e l o c i t y o f 5.48 k m s - 1 . The e p i c e n t r a l e r r o r was 150 m and t h e d e p t h e r r o r 110 m. T h i s i s a r a t h e r m i s l e a d i n g e r r o r e s t i m a t e s i n c e t h e v e l o c i t y was a l l o w e d t o v a r y . In s u b s e q u e n t h y p o c e n t r a l c a l c u l a t i o n s , t h e 5.48 kms" 1 v e l o c i t y was u s e d and c o r r e c t i o n s a p p l i e d t o c a l c u l a t e d h y p o c e n t e r s b a s e d on t h e e r r o r s f o u n d i n t h e b l a s t c o o r d i n a t e s . From t h e d a t a c o l l e c t e d d u r i n g t h e S u l l i v a n program, 24 h y p o c e n t r e s and 32 e p i c e n t r e s were d e t e r m i n e d . I n t e r p r e t a t i o n o f t h e e a r t h q u a k e l o c a t i o n s i n terms of s t r u c t u r e d i d not a g r e e i n d e t a i l w i t h g e o l o g i c a l t h i n k i n g . However t h e r e s u l t s were s u f f i c i e n t l y i n t e r e s t i n g t o s u g g e s t t h a t f a u l t s c o u l d be mapped u s i n g m i c r o e a r t h q u a k e s , p r o v i d e d t h e m o n i t o r i n g p e r i o d was s u f f i c i e n t l y l o n g . (b) UBC 1976-77 Program D u r i n g t h e p e r i o d November 1976 - J a n u a r y 1977 a s i n g l e c h a r t r e c o r d i n g s e i s m o g r a p h was o p e r a t e d i n t h e M o r r i s o n s u b d i v i s i o n , a p p r o x i m a t e l y 4 km from t h e m i n i n g a c t i v i t y ( E l l i s , 1977). The o b j e c t i v e s o f t h i s p r o g r am were f i r s t l y t o d e t e r m i n e t h e r a t e of o c c u r r e n c e o f l o c a t a b l e s e i s m i c e v e n t s , and i f p o s s i b l e t h e s o u r c e - r e c e i v e r d i s t a n c e and R i c h t e r m a g n i t u d e s , and s e c o n d l y t o f u r t h e r examine t h e f e a s i b i l i t y o f u s i n g e a r t h q u a k e s t o l o c a t e f a u l t s a t t h i s s i t e . The p r i n c i p a l f i n d i n g s were t h a t t h e o c c u r r e n c e r a t e o f l o c a t a b l e e v e n t s was a b o u t 70 p e r month i n t h e range from R i c h t e r M a g n i t u d e 0.0 t o 1.4 i e . s i m i l a r t o t h e r a t e f o u n d by S e n t u r i o n ; t h a t t h e a c t i v i t y d r o p p e d v e r y s i g n i f i c a n t l y on weekends when t h e mine was n o t i n o p e r a t i o n ; and t h a t t h e 14 s e i s m i c i t y was n o t h i g h l y c o r r e l a t e d w i t h s h i f t end b l a s t i n g p e r i o d s . The upper s i z e l i m i t of most e v e n t s was a p p r o x i m a t e l y m a g n i t u d e 1.4, w h i c h i s l e s s t h a n t h e upper s i z e l i m i t o f 2.5 t o 3.0 o b s e r v e d by McGarr e t a l (1975) f o r e v e n t s a t t h e E a s t Rand P r o p r i e t a r y M i n e . A s t a n d a r d way o f p r e s e n t i n g t h e d a t a i s t o p l o t e v e n t m a g n i t u d e v e r s u s t h e l o g of t h e number of e v e n t s r e c o r d e d a t t h a t m a g n i t u d e ( l o g f r e q u e n c y ) . The s l o p e of t h e l i n e i s known a s t h e b - v a l u e , t h e h i g h e r t h e s l o p e t h e more e v e n t s r e c o r d e d a t t h e l o w e r m a g n i t u d e s v e r s u s t h e h i g h e r m a g n i t u d e s . A b - v a l u e of -1.0 was d e t e r m i n e d f o r t h e S u l l i v a n Mine a r e a w h i c h i s h i g h e r t h a n t h o s e f o u n d by McGarr and G r e e n (1978) i n t h e E a s t Rand P r o p r i e t a r y M i n e . S c h o l z (1968) shows t h a t t h e b - v a l u e i s s t r o n g l y d e p e n d e n t on t h e s t a t e of s t r e s s . As s t r e s s i s i n c r e a s e d t h e e v e n t s become s t a t i s t i c a l l y l a r g e r , t h a t i s t h e b - v a l u e s become l o w e r . A l t h o u g h s h a l l o w i t c o u l d n o t be d e t e r m i n e d whether t h e o b s e r v e d s e i s m i c i t y was c l o s e l y r e l a t e d t o t h e a c t i v e m i n i n g f a c e s o r more b r o a d s c a l e . From t h i s p r o g r a m i t was c l e a r t h a t a d d i t i o n a l s t u d i e s a t t h e S u l l i v a n Mine were r e q u i r e d t o d e t e r m i n e whether h y p o c e n t r e l o c a t i o n s a r e a v i a b l e way of f a u l t l o c a t i o n a t t h i s s i t e . The UBC 1980 S u l l i v a n Mine f i e l d e x p e r i m e n t , w h i c h i s t h e s u b j e c t o f t h i s t h e s i s , i s a s u b s e q u e n t t h o r o u g h i n v e s t i g a t i o n b a s e d on t h e f i n d i n g s of t h e 1976-77 p r o g r a m . 1 5 CHAPTER 2: THE SULLIVAN MINE The g e o l o g y o f t h e S u l l i v a n Mine w i l l be d e a l t w i t h f r o m t h r e e b a s i c a s p e c t s f o r t h e p u r p o s e s o f t h i s s t u d y , r a n g i n g f r o m t h e l o c a l s c a l e t o t h e r e g i o n a l s c a l e and c o n c e n t r a t i n g on t h e s t r u c t u r a l f e a t u r e s . The f i r s t s e c t i o n d i s c u s s e s b r i e f l y t h e l o c a l mine g e o l o g y and summarizes t h e i n f o r m a t i o n t o d a t e on t h e l o c a l f a u l t s i n and a r o u n d t h e mine a r e a ; t h e s e c o n d s e c t i o n i s a summary o f t h e s t r u c t u r a l h i s t o r y r e c o n s t r u c t e d f o r t h e mine r e g i o n ; and t h e t h i r d s e c t i o n d i s c u s s e s on a b r o a d s c a l e t h e s e t t i n g and d e v e l o p m e n t o f t h e S u l l i v a n o r e b o d y i n t h e t e c t o n i c h i s t o r y o f w e s t e r n Canada i n t e r m s of a p l a t e t e c t o n i c m o d e l . In o r d e r t o a s c e r t a i n t h e p r e s e n t b r o a d s c a l e s t r e s s p a t t e r n i n t h e S u l l i v a n Mine a r e a , i t i s p a r t i c u l a r l y i m p o r t a n t t o u n d e r s t a n d t h e d e v e l o p m e n t o f t h e r e g i o n a l s t r e s s r e g i m e t h r o u g h t o t h e l a s t e x t e n s i o n a l p hase i n t h e s o u t h e a s t e r n C o r d i l l e r a w h i c h t o o k p l a c e 55 t o 5 m i l l i o n y e a r s b e f o r e p r e s e n t (Ma) d u r i n g t h e Eocene t o M i o c e n e ( P r i c e , 1977). 16 2.1 GEOLOGY AND STRUCTURE OF OREBODY The S u l l i v a n o r e b o d y i s l o c a t e d i n l o w e r P u r c e l l s e d i m e n t s of H e l i k a n age (1500 t o 1000 Ma) a t t h e c o n t a c t between t h e Lower A l d r i d g e and M i d d l e A l d r i d g e f o r m a t i o n s (Ransom, 1977). The A l d r i d g e f o r m a t i o n i s a 4,500 m t h i c k s t a c k o f f l y s c h o i d s e d i m e n t s c o n s i s t i n g of a r g i l l i t e s , s i l t s and q u a r t z wackes r a n g i n g i n t h i c k n e s s f r o m f i n e l a m i n a e t o m a s s i v e u n i t s 12 m t h i c k (Ransom, 1977). The A l d r i d g e f o r m a t i o n i s metamorphosed t o m i d d l e t o upper G r e e n s c h i s t f a c i e s (Hoy e t a l , 1981). The o r e b o d y and s u r r o u n d i n g s e d i m e n t s a r e c u t by numerous f a u l t s . The major ones a r e shown i n F i g u r e 1.2 and F i g u r e 2.1 p r o v i d e s a more d e t a i l e d p i c t u r e o f t h e f a u l t s w i t h i n t h e mine a r e a . The f a u l t s a r e c l a s s i f i e d i n t o two major t y p e s by Ransom ( 1 9 7 7 ) : " ( i ) N o r t h d i p p i n g , e a s t - w e s t s t r i k i n g n o r m a l f a u l t s s u c h as t h e K i m b e r l e y and H i d d e n Hand f a u l t s . The K i m b e r l e y f a u l t d i p s 55°N w i t h an a p p a r e n t s t r a t i g r a p h i c d i s p l a c e m e n t o f 2000 m, n o r t h s i d e down. D r a g f o l d s i n t h e beds on e i t h e r s i d e o f , and c l o s e t o t h e f a u l t i n d i c a t e however t h a t t h e f a u l t was i n i t i a l l y a t h r u s t w i t h t h e n o r t h b l o c k r i d i n g o v e r t h e s o u t h . R i c e (1937) e x p l a i n s t h a t t h e f a u l t s t a r t e d as a t h r u s t , p r o b a b l y of no g r e a t d i s p l a c e m e n t , and l a t e r when f o r c e s c h a n g e d from c o m p r e s s i v e t o t e n s i l e t h e d i r e c t i o n o f movement r e v e r s e d and i t became a n o r m a l f a u l t o f much g r e a t e r d i s p l a c e m e n t . ( i i ) N o r t h e r l y t r e n d i n g n o r m a l f a u l t s t h a t d i p s t e e p l y west, s u c h as t h e S u l l i v a n , B u r c h e t t , S m i t h and E a s t f a u l t s ( F i g u r e 2 . 1 ) . The f a u l t s s t r i k e 10° t o 20° e a s t o f n o r t h and e x h i b i t west s i d e down d i s p l a c e m e n t s i n t h e o r e of up t o 25 m F i a u r e 2.1 F a u l t s w i t h i n t h e S u l l i v a n M i n e , F o o t w a l l T r a c e . The d a s h e d l i n e i n d i c a t e s t h e o r e b o d y edge and t h e d o t t e d l i n e shows t h e e x t e n t of t h e open p i t . Number a d j a c e n t t o t h e f a u l t t r a c e i n d i c a t e t h e d i p of t h e f a u l t p l a n e , ( m o d i f i e d f r o m H a m i l t o n e t a l , 1 9 8 2 ) . 18 w i t h l a r g e r d i s p l a c e m e n t s on s i m i l a r l y o r i e n t e d f a u l t s l o c a t e d e a s t o f t h e o r e b o d y (Hoy e t a l ,1981). The f a u l t s i n t h i s c l a s s a r e known as S u l l i v a n - S t y l e . 2.2 STRUCTURAL HISTORY The s t r u c t u r a l h i s t o r y o f t h e mine r e g i o n i s o f p a r t i c u l a r i n t e r e s t t o t h e p r e s e n t s t u d y and i s summarized f r o m v a r i o u s s t u d i e s as f o l l o w s : ( i ) N o r t h e a s t t r e n d i n g s y n d e p o s i t i o n a l basement f a u l t s a r e b e l i e v e d t o have l o c a l l y c o n t r o l l e d t h e i n i t i a l d e p o s i t i o n o f t h e P u r c e l l s e d i m e n t s (Hoy, 1979). E v i d e n c e s u g g e s t i n g t h i s i n c l u d e s l o c a l v a r i a t i o n s i n s e d i m e n t t h i c k n e s s e s , r a p i d l a t e r a l f a c i e s c h a n g e s and i n t r a f o r m a t i o n a l c o n g l o m e r a t e s (Hoy e t a l 1981, 1982) and t o u r m a l i n i z a t i o n n e a r t h e s e f a u l t s ( E t h i e r e t a l , 1976). ( i i ) The c u r r e n t and most w i d e l y h e l d model f o r S u l l i v a n o r e d e p o s i t i o n i s d e s c r i b e d i n d e t a i l by Ransom (1977) and Hoy e t a l ( 1 9 8 1 ) . The S u l l i v a n d e p o s i t formed as m e t a l - b e a r i n g s o l u t i o n s a s c e n d e d t h r o u g h a s y n s e d i m e n t a r y f a u l t and f r a c t u r e s y s t e m . D i s c r e t e s u l p h i d e c r y s t a l s were spewed o u t , a s w e l l as m e t a l i o n s w h i c h c o m b i n e d w i t h s e a w a t e r s u l p h a t e under r e d u c i n g c o n d i t i o n s t o p r e c i p i t a t e a s s u l p h i d e s on t h e ' A l d r i d g e s e a f l o o r . The m e t a l z o n a t i o n , c o n s i s t e n t w i t h t h e above model, i n d i c a t e s d e p o s i t i o n o f l e a d , s i l v e r and t i n c l o s e r t o t h e v e n t , t h o u g h t t o be r e p r e s e n t e d by a r e a s of c h a o t i c b r e c c i a , w i t h z i n c b e coming more c o n c e n t r a t e d t h a n l e a d f u r t h e r away from t h e v e n t (Hoy e t a l , 1981). 19 ( i i i ) M c C l a y (198 1) d e s c r i b e s t h r e e p h a s e s of f a u l t i n g and f o l d i n g t h a t o c c u r r e d f o l l o w i n g o r e d e p o s i t i o n ; t h e s e a r e Phase 1: i s o c l i n a l f o l d s w i t h a x i a l p l a n e s p a r a l l e l t o b e d d i n g p l a n e s and n o r t h t r e n d i n g f o l d a x e s . Phase 2: r e l a t i v e l y open f o l d s w i t h g e n t l e n o r t h o r s o u t h p l u n g e s w i t h w e s t e r l y d i p p i n g a x i a l p l a n e s and w e s t e r l y d i p p i n g t h r u s t s . The f i r s t two p h a s e s a r e of p r e e a r l y C r e t a c e o u s age and c o r r e l a t e w i t h t h e d e v e l o p m e n t o f t h e P u r c e l l A n t i c l i n o r i u m . Phase 3: f o l d s a r e a s s o c i a t e d w i t h e a s t e r l y d i p p i n g t h r u s t f a u l t s w h i c h d i s p l a c e E a r l y C r e t a c e o u s l a m p r o p h y r e d y k e s d a t e d a t 150 Ma. ( i v ) The S u l l i v a n - s t y l e n o r m a l f a u l t s shown i n F i g u r e 2.1 c u t a l l t h e e a r l i e r f e a t u r e s and a r e b e l i e v e d t o be due t o r e g i o n a l e x t e n s i o n d u r i n g t h e E o c e n e (K.McClay, p e r s o n a l c o m m u n i c a t i o n , 1981) 2.3 SETTING IN THE TECTONIC HISTORY OF WESTERN CANADA , A PLATE TECTONIC MODEL The C a n a d i a n C o r d i l l e r a c o n s i s t s o f f i v e d i s t i n c t g e o l o g i c a l and p h y s i o g r a p h i c p r o v i n c e s or b e l t s ( F i g u r e 1.1) w h i c h a r e , f r o m e a s t t o west; t h e Rocky M o u n t a i n B e l t , Omineca C r y s t a l l i n e B e l t , I n t e r m o n t a n e B e l t , C o a s t P l u t o n i c Complex and I n s u l a r B e l t . The b e l t s f o r m s u b - p a r a l l e l z o n e s o c c u p y i n g much of B r i t i s h C o l u m b i a from t h e edge o f t h e N o r t h A m e r i c a n c r a t o n , l o c a t e d r o u g h l y a t t h e B . C . - A l b e r t a b o r d e r , t o t h e p r e s e n t c o a s t l i n e . W i t h t h e e x c e p t i o n o f t h e Rocky M o u n t a i n B e l t , t h e p r e s e n t 20 c o n f i g u r a t i o n of t h e r e m a i n d e r of B r i t i s h C o l u m b i a i s b e l i e v e d t o be due t o t h e c o l l i s i o n and a c c r e t i o n of a l l o c t h o n o u s t e r r a n e s r a f t e d i n f r o m t h e s o u t h - w e s t (Monger and P r i c e , 1979) E v o l u t i o n of t h e C a n a d i a n C o r d i l l e r a began a p p r o x i m a t e l y 1500 Ma i n t h e m i d d l e P r o t e r o z o i c w i t h i n i t i a l A t l a n t i c - t y p e r i f t i n g o f an o l d e r P r e c a m b r i a n c o n t i n e n t a l l a n d mass i n t o t h e N o r t h A m e r i c a n c r a t o n and i t s c o u n t e r p a r t , t h e S i b e r i a n P l a t f o r m (Monger an d P r i c e , 1979) F i g u r e 2.2 s pans t h e t i m e p e r i o d from m i d d l e P r o t e r o z o i c (1500 Ma) t o mid T r i a s s i c (230 Ma) a n d summarizes, i n s i m p l i f i e d f o r m , t h e m a t e r i a l p r e s e n t e d by Monger e t a l ( 1 9 7 2 ) , Monger and P r i c e ( 1 9 7 9 ) , and o t h e r s . F i g u r e 2.2 shows s c h e m a t i c a l l y t h e i n i t i a l f o r m a t i o n of t e n s i o n a l r i f t b l o c k s ( i n p a r t s A and B) d u r i n g t h e m i d d l e P r o t e r o z o i c ; p r o g r a d a t i o n from t h e N o r t h A m e r i c a n c o n t i n e n t a l m a r g i n of a n o r t h - e a s t e r l y t a p e r i n g m i o g e o c l i n a l wedge of P u r c e l l s e d i m e n t s w h i c h d i s c o r d a n t l y o v e r l a p s e a r l i e r s t r u c t u r e s of t h e c r a t o n i c basement ( p a r t s B and C ) ; c o n t i n u e d p r o g r a d a t i o n o f t h e Windermere s e d i m e n t s d u r i n g t h e l a t e r P r o t e r o z o i c u n t i l t h e M i d d l e D e v o n i a n , 380 Ma ( p a r t D ) ; s u b s i d e n c e o f t h e c r a t o n edge d u r i n g t h e L a t e D e v o n i a n f o l l o w e d by t h e o n l a p o f c a r b o n a t e s h a l e a n d - c h e r t f a c i e s s t r a t i g r a p h i c a l l y on t o p o f t h e o l d e r m i o g e o c l i n a l s t r a t a ( p a r t E ) . I t i s i n t e r e s t i n g t o n o t e t h a t t h e d u r a t i o n s panned by F i g u r e 2.2 r e p r e s e n t s o v e r 4/5 of t h e t o t a l t i m e o f f o r m a t i o n o f t h e C o r d i l l e r a of w e s t e r n Canada as i t s t a n d s t o d a y . The o r i g i n o f a change from b a s i c a l l y e x t e n s i o n a l t o a c o m p r e s s i o n a l regime w i t h o v e r t h r u s t i n g and s u b d u c t i o n as shown 21 TT Domal u p l i f t , formation of A t l a n t i c - t y p e t e n s i o n a l r i f t blocks sometime before 1500 Ma. B. Development of a north-e a s t e r l y tapering wedge of P u r c e l l Sediment prograding from the North American craton (Modern analogue: East A f r i c a n r i f t system) c C A R B O N A F E B A N K T I D A L F L A T \ T U R B I D I T E Continued progradation of the P u r c e l l during the middle P r o t e r o z o i c ; development of sea f l o o r ; i n t r u s i o n of b a s i c v o l c a n i c s . (Modern analogue: Red Sea) D. Truncation of the P u r c e l l , continued d e p o s i t i o n of Windermere sediments west of the P u r c e l l from the l a t e r P r o t e r o z o i c u n t i l the Middle Devonican, (-380 Ma) . S I B E R I A N -P L A T F O R M N O R T H A M E R I C A N C R A T O N Subsidence of the craton p o s s i b l y due to movement away from the spreading r i d g e ; onlap of shale and carbonate f a c i e s of the Late Devonian to Middle T r i a s s i c (380 - 230 Ma). F i g u r e 2 . 2 Schematic E v o l u t i o n of the Canadian C o r d i l l e r a ( 1 5 0 0 - 230 Ma), based on the d e s c r i p t i o n s of Monger and P r i c e , 1979. 22 Development of westerly t h r u s t i n g , or subduction under the North American cra t o n ; p o s s i b l y i n response to i n i t i a l opening of the A t l a n t i c Ocean p r i o r to 165 Ma. 2. Emplacement of the S t i k i n e and associated terranes i n the p e r i o d from l a t e s t T r i a s s i c to Middle J u r a s s i c (230 - 165 Ma ). 3. Associated i n t r u s i o n o f g r a n i t i c rocks i n the Omineca C r y s t a l l i n e B e l t during the Middle to Late J u r a s s i c . 4. Emplacement of Wrangellia during the Middle J u r a s s i c to Middle Cretaceous (165 - 95 Ma ). 5. Associated i n t r u s i o n of g r a n i t i c rocks i n the Coast P l u t o n i c Complex during, and j u s t p r i o r t o , the Late Cretaceous to Paleocene i n t e r v a l (95 - 20 Ma ). 6. Associated f o l d i n g and t h r u s t i n g i n the Rocky Mountain B e l t . F i g u r e 2.3 S c h e m a t i c E v o l u t i o n of t h e C a n a d i a n C o r d i l l e r a (230 - 95 Ma). The p l a n map shows t h e p r e s e n t c o n f i g u r a t i o n and a r e a l e x t e n t of the' m a j o r a 1 l o c h t h o n o u s t e r a n e s , m o d i f i e d f r o m Monger e t a l , 1972; Monger and P r i c e , 1979. 23 i n F i g u r e 2.3 i s u n c e r t a i n . T h i s change o c c u r r e d sometime i n t h e p e r i o d from l a t e s t T r i a s s i c t o M i d d l e J u r a s s i c (230 Ma t o 165 Ma) w h i c h i s r o u g h l y c o i n c i d e n t w i t h t h e i n i t i a l major o p e n i n g o f t h e A t l a n t i c Ocean a t a b o u t 165 Ma (Monger and P r i c e , . 1979). Monger and P r i c e (1979) f e e l t h a t t h e s e c o m p r e s s i o n a l f e a t u r e s may r e f l e c t r e l a t i v e p l a t e m o t i o n c h a n g e s between t h e N o r t h A m e r i c a n P l a t e and o c e a n i c p l a t e s t o t h e west i n r e s p o n s e t o t h e o p e n i n g of t h e A t l a n t i c Ocean. They d e s c r i b e two major a c c r e t i o n e v e n t s , e a c h one f o l l o w e d by westward s t e p p i n g o f t h e s u b d u c t i o n z o n e . T h i s i s i d e a l i z e d i n F i g u r e 2.3. Emplacement of t h e f i r s t e x o t i c t e r r a n e , t h e S t i k i n e B l o c k ( l o c a t e d a l m o s t w h o l l y w i t h i n t h e p r e s e n t I n t e r m o n t a n e B e l t ) o c c u r r e d i n l a t e s t T r i a s s i c t o M i d d l e J u r a s s i c (230 t o 165 Ma) w i t h a s s o c i a t e d u p l i f t and i n t r u s i o n o f g r a n i t i c r o c k s i n t h e Omineca C r y s t a l l i n e B e l t i n t h e M i d d l e and L a t e J u r a s s i c (165 t o 140 Ma), ( F i g u r e 2.3 p a r t s 1,2,3) The s e c o n d e x o t i c t e r r a n e , W r a n g e l l i a ( l o c a t e d i n t h e I n s u l a r B e l t ) was e m p l a c e d d u r i n g t h e E a r l y C r e t a c e o u s (140 t o 100 Ma) a c c o m p a n i e d by u p l i f t and s u b d u c t i o n r e l a t e d magmatism i n t h e C o a s t P l u t o n i c Complex ( F i g u r e 2.3 p a r t s 4 , 5 ) . T h i s was a c c o m p a n i e d by m a j o r c r u s t a l s h o r t e n i n g i n t h e form o f i m b r i c a t e t h r u s t f a u l t i n g and f o l d i n g i n t h e Rocky M o u n t a i n B e l t ( F i g u r e 2.3 p a r t 6 ) . F i g u r e 2.3 s p a n s t h e p e r i o d f r o m L a t e T r i a s s i c t o L a t e C r e t a c e o u s (230 t o 95 Ma) a f t e r w h i c h t i m e " w i d e s p r e a d s u b d u c t i o n of o c e a n i c c r u s t c e a s e d and a t r a n s f o r m b o u n d a r y was e s t a b l i s h e d , now r e p r e s e n t e d by Queen C h a r l o t t e - F a i r w e a t h e r f a u l t s y s t e m " (Monger an d P r i c e , 1979). D u r i n g E o c e n e , O l i g o c e n e and M i o c e n e t i m e (55 t o 5 Ma) 24 r e g i o n a l e x t e n s i o n . , p o s s i b l y i n r e s p o n s e t o t h e c e s s a t i o n of s u b d u c t i o n , l e d t o t h e f o r m a t i o n of l i s t r i c n o r m a l f a u l t s , o f f s e t t i n g o l d e r s t r u c t u r e s i n t h e C o r d i l l e r a o f s o u t h e a s t e r n B r i t i s h C o l u m b i a ( P r i c e , 1977). Summary (a) The S u l l i v a n orebody' i s b e l i e v e d t o have been h o s t e d i n t h e d e e p w a t e r p o r t i o n o f t h e A t l a n t i c - t y p e c o n t i n e n t a l t e r r a c e wedge of P u r c e l l s e d i m e n t s p r o g r a d i n g f r o m t h e a n c i e n t N o r t h A m e r i c a n c r a t o n d u r i n g t h e p e r i o d r e p r e s e n t e d by F i g u r e 2.2 C (Ransom, 1977). (b) The p h a s e s of c o m p r e s s i o n a l d e f o r m a t i o n i n t h e S u l l i v a n f r o m p r e - E a r l y C r e t a c e o u s t o l a t e - E a r l y C r e t a c e o u s , d e s c r i b e d by M c C l a y ( 1 9 8 1 ) , a r e c o i n c i d e n t w i t h emplacement of W r a n g e l l i a d u r i n g t h e M i d d l e J u r a s s i c t o M i d d l e C r e t a c e o u s , and c o n s e q u e n t d e f o r m a t i o n i n t h e Rocky M o u n t a i n B e l t . ( c ) K. M c C l a y ( p e r s o n a l c o m m u n i c a t i o n , 1981) b e l i e v e s S u l l i v a n - s t y l e n o r m a l f a u l t i n g o c c u r r e d i n r e s p o n s e t o r e g i o n a l e x t e n s i o n i n t h e s o u t h - e a s t e r n C o r d i l l e r a d u r i n g t h e t i m e f r o m t h e E ocene t o M i o c e n e d e s c r i b e d by P r i c e ( 1 9 7 7 ) . I t i s p o s s i b l e t h a t t h e change from t h r u s t t o n o r m a l m o t i o n a l o n g t h e K i m b e r l e y f a u l t ,as d e s c r i b e d by R i c e ( 1 9 3 7 ) , was a l s o f a c i l i t a t e d a t t h i s t ime. 25 2.4 ANALYSIS OF CONDITIONS NECESSARY FOR FAULT REACTIVATION AT THE SULLIVAN L e t us now examine t h e p o s s i b l e mechanisms of f a u l t r e a c t i v a t i o n t h a t would g e n e r a t e m i c r o e a r t h q u a k e a c t i v i t y i n t h e mine e n v i r o n m e n t . F i g u r e 2.4 e x p l a i n s i n t u i t i v e l y how we w o u l d FIGURE 2.4 Mechanisms f o r F a u l t R e a c t i v a t i o n i n t h e M i n e E n v i r o n m e n t . R e a c t i v a t i o n o f p r e - e x i s t i n g p l a n e s o f weakness; h a n g i n g w a l l o r r o o f c o l l a p s e above t h e mine and " u n w e i g h t i n g " i n t h e f o o t w a l l o r f l o o r . e x p e c t m i c r o e a r t h q u a k e a c t i v i t y t o be i n d u c e d by m i n i n g . As t h e o r e i s removed, m a t e r i a l w i l l move i n t o t h e v o i d s p a c e from b o t h a b o v e and b e l o w . Above t h e o r e b o d y , c o l l a p s e w i l l o c c u r a l o n g n o r m a l f a u l t s w h i c h may be p r e - e x i s t i n g p l a n e s of weakness, a l t h o u g h t h e i r d i s t r i b u t i o n i s g e n e r a l l y c o n t r o l l e d by t h e s t o p e s b e l o w . The s u r f a c e e x p r e s s i o n s of t h e l a r g e r of s u c h o c c u r r e n c e s a r e o v a l s h a p e d d e p r e s s i o n s o f c o n c e n t r i c , 26 e n - e c h e l o n n o r m a l f a u l t s . Below t h e o r e b o d y , m a t e r i a l w i l l move upwards by r e v e r s e f a u l t i n g i n r e s p o n s e t o t h e d e c r e a s e d o v e r b u r d e n p r e s s u r e . The m i c r o e a r t h q u a k e s w i l l l o c a t e where s t r e s s r e l e a s e , i n t h e f o r m of r u p t u r e and s l i d i n g , o c c u r s ; and i t i s l o g i c a l t o assume t h a t t h i s movement w i l l o c c u r a l o n g p r e - e x i s t i n g p l a n e s of weakness. Note t h a t F i g u r e 2.4 i g n o r e s t h o s e f r a c t u r e - g e n e r a t e d e v e n t s , d i s c u s s e d e a r l i e r , t h a t o c c u r a t t h e i mmediate mine f a c e s i n r e s p o n s e t o t h e l o a d s t r e n g t h o f t h e r o c k b e i n g e x c e e d e d i n t h e s e h i g h l y s t r e s s e d r e g i o n s . A more d e t a i l e d l o o k a t t h e m a g n i t u d e of t h e s t r e s s c h a n g e s i n v o l v e d a t t h e S u l l i v a n Mine c a n be c o n s i d e r e d f i r s t l y by e s t i m a t i n g t h e d i s t r i b u t e d l o a d removed. T o t a l mass removed = 114,000,000 t o n n e s (1920-1980) = 1 1 .4 x IO" 1 0 kg A r e a of Mine = 3 x 10 6 m 2 F o r c e = mass x g r a v i t a t i o n a l (9.8 ms" 2) a c c e l e r a t i o n = 11.4 x 1 0 1 1 newtons (N) The f o r c e a c t i n g i n an upward d i r e c t i o n p e r p e n d i c u l a r t o t h e r o c k s u r f a c e o v e r an a r e a o f 3 x 10 s m 2 means a d i s t r i b u t e d l o a d removed of 4 x 10 5 Nm"2 o r 4 b a r s . T h i s f i g u r e i s o f t h e same o r d e r of m a g n i t u d e a s t h a t of 7 b a r s c a l c u l a t e d by Pomeroy e t . a l (1976) f o r t h e d i s t r i b u t e d l o a d removed f r o m W a p p i n g e r s F a l l s Q u a r r y i n a 20 y e a r p e r i o d ; and a l s o t h a t o f a b o u t 7 b a r s c a l c u l a t e d by Gough and Gough (1970) f o r t h e downward n o r m a l s t r e s s u nder t h e d e e p e s t p a r t of Lake K a r i b a f o r m e d by t h e damming o f t h e Zambezi R i v e r i n A f r i c a . T h e s e f i g u r e s , however, a r e s i g n i f i c a n t l y l e s s t h a n t h e l o a d a p p l i e d 27 by an a v e r a g e woman (mass 60 kg) w e a r i n g s t i l e t t o h e e l s ( e a c h of 1 cm 2 a r e a ) , t h a t i s 30 b a r s . T h i s i s as f a r as r e s e a r c h e r s l i k e Gough and Gough (1970) and Pomeroy e t a l ( 1 9 7 6 ) , d e a l i n g w i t h o n l y s u r f a c e l o a d i n g and u n l o a d i n g , c o u l d c a r r y t h e i r c a l c u l a t i o n s ; t h e i n d u c e d s t r e s s e s a l o n e a r e i n s u f f i c i e n t t o c a u s e f a i l u r e . The i m p l i c a t i o n s of t h e i r f i n d i n g s w i l l be d i s c u s s e d l a t e r . I n t h e c a s e o f an u n d e r g r o u n d mine t h e d i f f e r e n t i a l s t r e s s e s between v a r i o u s a r e a s w i l l be f a r h i g h e r . F o r example, a t a p a r t i c u l a r p o i n t i n , s a y , t h e f l o o r o f a l a r g e s t o p e , t h e p r e s s u r e r e m o v a l c o r r e s p o n d s n o t o n l y t o t h e r e m o v a l o f t h e column o f o r e but a l s o t h e u n s u p p o r t e d column of r o c k above t h a t p o i n t . An i n c r e a s e d s t r e s s i s of c o u r s e f e l t e l s e w h e r e i n n e a r b y p i l l a r s (.Figure 2 . 5 ) . In t h e d e e p e r p a r t s o f t h e S u l l i v a n a t 900 m d e p t h t h e w e i g h t o f a 1 m by 1 m column o f r o c k o f . d e n s i t y 2.5 gm cm" 3 i s 2.25 x 10 6 kg. The p r e s s u r e i t a p p l i e s i s 2.25 x 10 7 Nm"2 o r 225 b a r s . So f o r a s t o p e t o p i l l a r r a t i o of 1 t o 1 t h e r e c o u l d be a l o a d d i f f e r e n c e of up t o 500 b a r s between c e r t a i n p o i n t s . T h i s i s now w i t h i n t h e r a n g e o f t h e s h e a r f a i l u r e s t r e n g t h o f q u a r t z - i t e s ( J u m i k i s , 1979, p. 108) . I t seems t h a t s l i d i n g c o u l d o c c u r p a r t i c u l a r l y i f p r e - e x i s t i n g p l a n e s o f weakness do e x i s t . Pomeroy e t a l (1967) and Gough and Gough (1970) s u g g e s t t h a t t h e man-made a c t i v i t y i s m e r e l y a t r i g g e r f o r e a r t h q u a k e a c t i v i t y o b s e r v e d a t e a c h o f t h e i r s t u d y a r e a s . S m i t h e t a l (1974) and McGarr e t a l (1975) a r r i v e a t t h e same c o n c l u s i o n i n o r d e r t o e x p l a i n t h e s e i s m i c e v e n t s o b s e r v e d away from t h e m i n i n g f a c e s . A n e c e s s a r y c r i t e r i o n i s e i t h e r t h e p r e - e x i s t e n c e 28 FIGURE 2.5 S c h e m a t i c R e d i s t r i b u t i o n o f t h e O v e r b u r d e n L o a d i n an U n d e r g r o u n d M i n e . The d a s h e d l i n e s e p a r a t e s r e g i o n s of s h e a r and i n d u c e d t e n s i l e s t r e s s f o l l o w i n g M c Garr e t a l ( 1 9 7 5 ) . o f s t o r e d s t r a i n e n e r g y f r o m a p r e v i o u s s t r e s s , t e c t o n i c o r o t h e r w i s e , or a p r e s e n t l y a c t i v e s t r e s s p a t t e r n . F i g u r e 2.6 shows t h e c o n f i g u r a t i o n s o f t h e t e c t o n i c s t r e s s f i e l d t h a t would a l l o w f a u l t r e a c t i v a t i o n i n t h e c a s e of a l o a d r e m o v a l , s u c h as c a u s e d by m i n i n g o r s u r f a c e q u a r r y i n g . The d i a g r a m s show t h e N a v i e r - C o u l o m b f a i l u r e e n v e l o p e g i v e n by t h e e q u a t i o n ( J u m i k i s , 1979), OVERLEAF: FIGURE 2,6 R e g i o n a l S t r e s s C o n f i g u r a t i o n s n e c e s s a r y t o a l l o w F a u l t R e a c t i v a t i o n due t o U n l o a d i n g . The s t i p p l e d a r e a s r e p r e s e n t o r e b o d i e s and t h e n o n - s t i p p l e d a r e a s i n d i c a t e t h a t t h e ore- has been removed. The e f f e c t o f u n l o a d i n g on t h e d i f f e r e n t p o s s i b l e s t r e s s c o n f i g u r a t i o n s (A, B & C) i s i n d i c a t e d by t h e d a s h e d Mohr c i r c l e s . A . REGIONAL COMPRESSION B . REGIONAL COMPRESSION C . R E G I O N A L T E N S I O N ( CT, H O R I Z O N T A L ) ( (X, , CTj HORIZONTAL ) ( CT, V E R T I C A L ) WITH REMOVED LOAD WITH REMOVED LOAD WITH REMOVED LOAD THRUST F A U L T I N G S T R I K E S L I P NORMAL F A U L T I N G S U P P R E S S E D 30 T = T 0 + (iC where, T = t h e a p p l i e d s h e a r s t r e s s a = t h e a p p l i e d n o r m a l o r a x i a l s t r e s s and T 0 and ti a r e r o c k d e p e n d e n t p a r a m e t e r s d e t e r m i n e d from l o a d i n g e x p e r i m e n t s . The d i f f e r e n c e between t h e maximum and minimum p r i n c i p a l s t r e s s e s , (tf, - <r 3), i s a l s o i n d i c a t e d i n F i g u r e 2.6 a s t h e d i a m e t e r of t h e Mohr c i r c l e . T h r e e s i t u a t i o n s may o c c u r ( F i g u r e 2.6 p a r t s A,B & C ) : A. In t h e c a s e o f an i n i t i a l c o m p r e s s i v e r e g i o n a l s t r e s s (maximum p r i n c i p a l s t r e s s a y h o r i z o n t a l ) u n i f o r m u n l o a d i n g due t o m i n i n g a c t i v i t y w o u l d s e r v e t o d e c r e a s e t h e downward d i r e c t e d minimum p r i n c i p a l s t r e s s e3 e n l a r g i n g t h e d i a m e t e r of t h e Mohr c i r c l e u n t i l i t becomes t a n g e n t t o t h e N a v i e r - C o u l o m b e n v e l o p e a t w h i c h p o i n t f a i l u r e o c c u r s by t h r u s t f a u l t i n g . An i n c r e a s e d , l o a d i n t h i s c a s e would m e r e l y s e r v e t o s t a b i l i z e t h e s i t u a t i o n by i n c r e a s i n g « 3 and t h u s d e c r e a s i n g t h e r a d i u s of t h e Mohr C i r c l e . B. I n t h e c a s e o f b o t h a, and <*3 b e i n g i n t h e h o r i z o n t a l p l a n e w i t h a2 a c t i n g downwards, a l o a d r e m o v a l , o r d e c r e a s e i n th e e f f e c t i v e o v e r b u r d e n p r e s s u r e , has t h e same e f f e c t a s l o w e r i n g t h e c o n f i n i n g p r e s s u r e . <r, - <r3 r e m a i n s t h e same but th e Mohr c i r c l e i s d i s p l a c e d t o w a r d s f a i l u r e w h i c h would o c c u r by s t r i k e s i i p f a u l t i n g . C. F o r an a r e a u n d e r r e g i o n a l t e n s i o n , t h a t i s a c t i n g v e r t i c a l l y , a d e c r e a s e d l o a d w i l l c a u s e an e f f e c t i v e d e c r e a s e i n w i t h r e s p e c t t o * 3 r e d u c i n g t h e r a d i u s of Mohr's c i r c l e and d r i v i n g t h e s y s t e m t o w a r d s s t a b i l i t y . Normal f a u l t i n g w i l l be s u p p r e s s e d , r a t h e r t h a n t r i g g e r e d by t h i s s i t u a t i o n . An 31 i n c r e a s e d l o a d would be n e c e s s a r y t o p e r m i t n o r m a l f a u l t i n g i n t h i s c a s e . U n l o a d i n g t h u s w i l l a l l o w t r i g g e r i n g of t h r u s t t y p e e v e n t s , as seen by Pomeroy e t a l (1976) and S m i t h e t a l ( 1 9 7 4 ) , or s t r i k e s l i p ; whereas i t w i l l i n h i b i t f a i l u r e by n o r m a l f a u l t i n g . I t i s i m p o r t a n t t o remember t h a t i n t h e c a s e of r e s e r v o i r s , t h e e f f e c t of t h e l o a d i n g i s c o n s i d e r e d s e c o n d a r y t o t h a t o f p o r e w a t e r p r e s s u r e (Snow, 1973). In p e r m e a b l e r o c k s t h e r e may be an i n c r e a s e i n p o r e water p r e s s u r e w h i c h c a u s e s t h e e f f e c t i v e p r i n c i p a l s t r e s s e s t o be r e d u c e d . B o t h n o r m a l and s t r i k e - s l i p f a u l t i n g may be t r i g g e r e d d u r i n g r e s e r v o i r f i l l i n g . Summary . In summary, f a u l t r e a c t i v a t i o n may o c c u r a t t h e S u l l i v a n Mine due t o d i f f e r e n t i a l s h e a r s t r e s s e s a l o n g p l a n e s o f weakness c l o s e t o t h e mine f a c e s . F a i l u r e by t h r u s t f a u l t i n g below t h e mine w i l l o n l y o c c u r i f r e g i o n a l s t r e s s i s p r e s e n t and i f i t i s c o m p r e s s i v e , t h a t i s w i t h t h e maximum p r i n c i p a l s t r e s s b e i n g h o r i z o n t a l . I f r e g i o n a l s t r e s s i s n o t p r e s e n t , t h e u n l o a d i n g due t o m i n i n g a c t i v i t y a l o n e i s i n s u f f i c i e n t t o r e a c t i v a t e t h r u s t f a u l t i n g . 32 CHAPTER 3: THE 1980 SULLIVAN MINE SEISMIC PROJECT 3.1 OBJECTIVES B a s e d on p r e v i o u s s t u d i e s and d i s c u s s i o n w i t h Cominco p e r s o n n e l , t h e 1980 f i e l d e x p e r i m e n t was d e s i g n e d w i t h t h e f o l l o w i n g s p e c i f i c o b j e c t i v e s i n mind: ( i ) t o d e t e r m i n e h y p o c e n t r e l o c a t i o n c a p a b i l i t y u s i n g known e x p l o s i o n s ; ( i i ) t o examine t h e d i s t r i b u t i o n of e v e n t s w i t h r e s p e c t t o the" a c t i v e mine a r e a s ; ( i i i ) t o d e t e r m i n e t h e r e l a t i o n s h i p between t h e l e v e l of m i c r o s e i s m i c a c t i v i t y and p e r i o d s of mine a c t i v i t y ; ( i v ) t o a c c u r a t e l y l o c a t e t h o s e e v e n t s away from t h e immediate mine f a c e s and d e t e r m i n e i f f a u l t s c an be d e l i n e a t e d . (v) To examine f o c a l mechanisms and d e t e r m i n e whether t h e y i n d i c a t e t h e p r e s e n c e o f a p r e - e x i s t i n g r e g i o n a l s t r e s s p a t t e r n as w e l l as m i n i n g i n d u c e d s t r e s s . 33 3.2 THE F I E L D EXPERIMENT The f i e l d p r o g r a m a t t h e S u l l i v a n Mine was c o n d u c t e d i n t h e p e r i o d f r o m June 2 t o J u l y 17, 1980. S i t e i n s p e c t i o n s were c a r r i e d out on t h e f i r s t day and t h e s e i s m o g r a p h a r r a y , c o n s i s t i n g of 7 d i g i t a l and 5 a n a l o g s t a t i o n s was e s t a b l i s h e d i n a 9 km by 6 km a r e a a b o u t t h e mine w i t h i n t h e f o l l o w i n g s i x d a y s . By .June 10 t h e network was o p e r a t i n g s m o o t h l y and d a t a was c o l l e c t e d a t a h i g h r a t e i n t h e f o l l o w i n g 4 weeks. The a r e a l d i s t r i b u t i o n o f t h e s e i s m o g r a p h s i s shown i n F i g u r e 1.2. The geophone l o c a t i o n a t e a c h s i t e was s u r v e y e d i n t o a known c o n t r o l p o i n t i n t h e mine r e f e r e n c e g r i d so t h a t t h e e r r o r i n s t a t i o n l o c a t i o n i s no more t h a n a b o u t 6 m (20 f e e t ) . S t a t i o n c o - o r d i n a t e s i n t e r m s o f t h e S u l l i v a n Mine g r i d and d e s c r i p t i v e l o c a t i o n s a r e g i v e n i n T a b l e 3.1. The immediate mine a r e a was w e l l s u r r o u n d e d by a 3 km by 3 km i n n e r n e t of s t a t i o n s (D39, D27, PMP, NAD, LOI, and PIT, shown i n F i g u r e 1.2) a s i t was a n t i c i p a t e d t h a t many of t h e e v e n t s w o u l d o c c u r i n t h a t r e g i o n . S e i s m o g r a p h s D39 and D27 were l o c a t e d i n t h e mine w o r k i n g s ( F i g u r e 1.3) w i t h D27 b e i n g a s deep a s p o s s i b l e , some 600 m below t h e s u r f a c e . The u n d e r g r o u n d s t a t i o n s were n e c e s s a r y t o i m p rove t h e f o c a l d e p t h r e s o l u t i o n s i n c e 2 - d i m e n s i o n a l s u r f a c e a r r a y s o n l y p r o v i d e weak c o n s t r a i n t s on t h e c a l c u l a t e d f o c a l d e p t h s . An o u t e r n e t of s t a t i o n s (SUL, MOR, NCN, MAT and BOG) i n c r e a s e d t h e r e g i o n o f c o v e r a g e a r o u n d t h e mine and e x t e n d e d i t a s y m m e t r i c a l l y westward. T h i s was f e l t t o be i m p o r t a n t as t h e K i m b e r l e y F a u l t i s a m a j o r r e g i o n a l f a u l t t h a t e x t e n d s t o t h e west i n t h i s a r e a ( F i g u r e 1.1) and i t s d e l i n e a t i o n c o u l d be o f e c o n o m i c i n t e r e s t . M i n i n g i n d u c e d s t r e s s would n o t be g r e a t TABLE 3.1 STATION LOCATION INSTRUMENTATION* REGION X ( f t ) Y (f) z ( f t ) SHF 3940 9020 3900 D S h i f t e r s s t a t i o n 3920 D39 4068 9705 3900 D 3958 d r i f t north D27 5710 13000 2700 D 2710 d r i f t north NCN 1515 3905 4385 D NCN plant PMP 2455 13810 5343 D Northeast of pump MOR 11145 3945 3715 D Morrison Subdivision NAD 5840 7482 4287 D East of new administration b u i l d i n g LOI 8637 12706 4346 D Lois Creek DDH s i t e SUL 8133 16860 5482 A S u l l i v a n H i l l Road MAT -15990 -850 4190 A Matthew Creek Road MRK -5060 12185 4630 A Mark Creek Road BOG -14250 16427 5457 A H i l l s i d e near DDH 409 Mark Creek PIT 2908 " 7690 4638 A West of Open P i t * D - D i g i t a l Geotech MCR 600 Seismograph A - Analog FM Tape Recording Seismograph T a b l e 3.1 Seismograph L o c a t i o n s i n terms of the Mine C o o r d i n a t e System. 35 enough t o a l l o w f a u l t r e a c t i v a t i o n a t t h i s d i s t a n c e f r o m t h e mine, as i n d i c a t e d by t h e s e l e c t e d s t u d i e s i n o t h e r m i n i n g a r e a s . However i f t h e r e i s any n a t u r a l movement a t p r e s e n t on any f a u l t away f r o m t h e i n f l u e n c e o f t h e mine, we would l i k e t o be a b l e t o l o c a t e t h e a s s o c i a t e d s e i s m i c a c t i v i t y as a c c u r a t e l y as p o s s i b l e . C a l c u l a t i o n s b a s e d on t h e " c o n t i n e n t a l a r e a " ( V a n c o u v e r I s l a n d , Puget Sound and Lower M a i n l a n d as d e f i n e d by M i l n e e t a l , 1978), i n d i c a t e t h e u n l i k e l i h o o d of r e c o r d i n g a n y s u c h n a t u r a l e v e n t s d u r i n g t h e p e r i o d o f t h e e x p e r i m e n t . F o r a 9 km by 6 km a r e a ( t h e s i z e of t h e s t u d y a r e a ) we would e x p e c t o n l y 1 e v e n t of m a g n i t u d e z e r o or g r e a t e r p e r 10 y e a r s . A S p r e n g n e t h e r MEQ-800 drum r e c o r d e r was m a i n t a i n e d a t s t a t i o n NCN f o r t h e d u r a t i o n of t h e e x p e r i m e n t so t h a t r a p i d v i s u a l o b s e r v a t i o n s of e v e n t s c o u l d be made. - I n p a r t i c u l a r , t h e i r c h a r a c t e r , r e l a t i v e s i z e and t i m i n g w i t h r e s p e c t t o t h e b a c k g r o u n d mine a c t i v i t y l e v e l s , c o u l d be seen a t a g l a n c e . F o r example s h i f t b r e a k b l a s t s o c c u r r e d a t s c h e d u l e d t i m e s , were l a r g e r t h a n t h e o t h e r e v e n t s and t h e i r a r r i v a l s t y p i c a l l y showed a maximum a m p l i t u d e w i t h i n t h e f i r s t few c y c l e s ( f r o n t end l o a d e d ) . 36 3.3 ARRAY INSTALLATION AND MAINTENANCE The a r e a s f o r e a c h s i t e were c a r e f u l l y s e l e c t e d -with t h e l o w e s t p o s s i b l e c u l t u r a l and b a c k g r o u n d n o i s e . E a c h s e i s m o m e t e r was i n s t a l l e d on b e d r o c k , t h u s m i n i m i z i n g l o c a l n a t u r a l n o i s e and e n s u r i n g t h e b e s t c o u p l i n g t o t h e g r o u n d . F o r t h e s t a t i o n s i n t h e mine, s i t e s were c h o s e n i n a r e a s away from m i n i n g a c t i v i t y . A t one s t a g e r e o c c u p a t i o n of t h e 3920 s h i f t e r s s t a t i o n by mine w o r k e r s r e q u i r e d t e m p o r a r y r e s i t i n g of SHF t o D39. Where p o s s i b l e , t h e s e i s m o m e t e r c a b l e was r a i s e d o f f t h e g r o u n d and r u n t h r o u g h t h e t r e e s a f t e r s e v e r a l d i s c o n n e c t i o n s a s a r e s u l t o f a n i m a l s gnawing t h e w i r e s . The r e c o r d i n g s y s t e m and power s u p p l y , two 12 v o l t c a r b a t t e r i e s , had t o be r o p e d t o g e t h e r , as b e a r s were c a u s i n g d i s t u r b a n c e s and t e r m i n a t i n g r e c o r d i n g by moving or o v e r t u r n i n g t h e equipment a t a l l but t h e two u n d e r g r o u n d s i t e s . F u r t h e r , r e p e l l e n t was s p r a y e d on t h e e quipment c a s i n g s f o l l o w i n g r e p e a t e d a t t e m p t s by p o r c u p i n e s t o e a t t h e wooden b a t t e r y and a m p l i f i e r boxes a t one s i t e . The s t a t i o n s were c o v e r e d w i t h p l a s t i c s h e e t i n g t o keep out m o i s t u r e and a i d c a m o u f l a g i n g . The a n a l o g s i t e s r e q u i r e d s e r v i c i n g e v e r y 5 d a y s t o change t a p e s and b a t t e r i e s . The d i g i t a l s y s t e m s however r e q u i r e d more c o n s t a n t m a i n t e n a n c e as s u f f i c i e n t e v e n t s were r e c o r d e d t o f i l l up t h e t a p e s e v e r y 2 t o 3 d a y s . A l s o t h e c r y s t a l c l o c k s had a s i g n i f i c a n t d r i f t r a t e ( A p p e n d i x 1) s u c h t h a t i t was d e s i r a b l e t o v i s i t t h e s i t e s a s o f t e n as p o s s i b l e , and a t most 2 d a y s a p a r t , t o c a l i b r a t e t h e c l o c k s w i t h WWV r a d i o t i m e . The d i g i t a l s y s t e m s i n t h e mine were v i s i t e d t w i c e a week. As r a d i o r e c e p t i o n was i m p o s s i b l e u n d e r g r o u n d , t h e i r c l o c k s were s e t by 37 c a r r y i n g i n a n o t h e r s y s t e m t h a t was c a l i b r a t e d t o WWV i m m e d i a t e l y p r i o r t o , and f o l l o w i n g t h e u n d e r g r o u n d v i s i t . The drum r e c o r d e r r e q u i r e d a d a i l y c h a r t p a p e r c h a n g e . 3.4 INSTRUMENTATION ( i ) A n a l o g S y s t e m s : The o u t p u t o f a 1 Hz s e i s m o m e t e r i s a m p l i f i e d and p r e s e n t e d t o a 7 - c h a n n e l FM t a p e r e c o r d e r a t 4 g a i n l e v e l s s e p a r a t e d by 12 db t o e x t e n d t h e b a s i c 35 db dynamic r a n g e o f t h e r e c o r d i n g s y s t e m . The maximum g a i n s e t t i n g was c h o s e n t o b r i n g t h e s e i s m i c b a c k g r o u n d n o i s e w e l l above t h e t a p e n o i s e l e v e l . P r i m a r y t i m i n g i s by r e c o r d i n g o f WWVB s i g n a l w i t h s e c o n d a r y t i m i n g p r o v i d e d by a c r y s t a l c o n t r o l l e d c l o c k i n c a s e o f t h e r a d i o s i g n a l f a d i n g . The f r e q u e n c y r e s p o n s e o f t h i s s y s t e m i s shown i n F i g u r e 3.1 A. One d i s a d v a n t a g e o f t h i s s y s t e m i s t h e e x t e n d e d low f r e q u e n c y r e s p o n s e . The s h a r p h i g h f r e q u e n c y o n s e t s t h e r e f o r e r i d e on t o p of t h e l o n g e r p e r i o d e n e r g y . ( i i ) D i g i t a l S y s t e m s : The d i g i t a l s e i s m o g r a p h s a r e G e o t e c h MCR-600 d i g i t a l e v e n t r e c o r d i n g s e i s m o g r a p h s w i t h 72 db dynamic r a n g e f o r w h i c h i n p u t was p r o v i d e d by 1 Hz s e i s m o m e t e r s . The s a m p l i n g r a t e was s e t a t 150 Hz and p a s s b a n d s e i t h e r 5 t o 25 Hz or 10 t o 25 Hz. The f r e q u e n c y r e s p o n s e o f t h i s s y s t e m i s shown i n F i g u r e 3.1 B. T y p i c a l l y t h e c r i t e r i o n u s e d f o r e v e n t d e t e c t i o n was t h a t t h e s h o r t t e r m (0.213 s) a v e r a g e t o l o n g t e r m (6.83 s) s i g n a l r a t i o was g r e a t e r t h a n o r e q u a l t o 6. T h i s p r o v i d e d h i g h q u a l i t y r e c o r d s and f i l l e d d i g i t a l t a p e s a t a m a x i m a l l y s e r v i c e a b l e r a t e ( i . e . e v e r y 2 t o 3 d a y s ) . T h i s was our f i r s t f i e l d d e p l o y m e n t o f t h e s e new d i g i t a l i n s t r u m e n t s and UBC FM SYSTEM AT FULL GflJN (Hh]2 DB) 10-' 3 5 7 10° 3 5 7 ] 0 l 3 5 7 10* FREQUENCY (HZ) A V e l o c i t y s e n s i t i v i t y o f UBC FM System a t a m p l i f i e r g a i n o f 106 db ( i . e . HI = 94 db). FREQUENCY (HZ) B V e l o c i t y s e n s i t i v i t y o f UBC GEOTECH MCR 600 system a t 90 db g a i n f o r l o w - c u t f r e q u e n c i e s o f 5 Hz and 10 Hz as used i n the e x p e r i m e n t . F i g u r e 3 .1 V e l o c i t y S e n s i t i v i t y of UBC S e i s m o g r a p h S y s t e m s . co 39 i n d e e d one of the e a r l i e s t a p p l i c a t i o n s of MCR-600's. As e x p e c t e d , some time was spent d e f i n i n g the a p p r o p r i a t e parameters f o r t r i g g e r i n g and s e v e r a l t e c h n i c a l problems a r o s e , t y p i c a l of e a r l y model equipment (our l o w e s t s e r i a l number was 006).. In a m i c r o s e i s m i c i t y experiment f/ the weakest p a r t of the system i s the c r y s t a l c l o c k which s y s t e m a t i c a l l y d r i f t s due t o t e m p e r a t u r e v a r i a t i o n and a g i n g of the c r y s t a l . The d r i f t measurements made on U n i t 008 a r e shown by the symbols i n F i g u r e 3.2. A t y p i c a l d r i f t r a t e of about 0.050 s per day i s o b s e r v e d w i t h s i g n i f i c a n t v a r i a t i o n s from l i n e a r i t y . D u r i n g the d a t a p r o c e s s i n g , the o b s e r v e d time of each f i r s t a r r i v a l was c o r r e c t e d assuming l i n e a r d r i f t between time c h e c k s . Appendix 1 shows t h a t t h i s assumption i s adequate w i t h r e s p e c t t o c r y s t a l a g i n g and a l s o l i n e a r d r i f t due t o d e p a r t u r e of the mean tem p e r a t u r e from the c r y s t a l c a l i b r a t i o n t e m p e r a t u r e . The problems a r i s e due t o the d i u r n a l temperature c y c l e which i s undersampled and not o b v i o u s l y v i s i b l e i n F i g u r e 3.2. For example the c l i m a t o l o g i c a l d a t a f o r K i m b e r l e y suggest a d a i l y s i n u s o i d a l - l i k e v a r i a t i o n w i t h an a m p l i t u d e of 0.013 s. V a r i a t i o n s of the mean d a i l y temperature cause e r r o r s of s i m i l a r s i z e . Thus the c l o c k d r i f t c u r v e s of F i g u r e 3.2 a r e e x p l a i n a b l e i n terms of t h e r m a l d r i f t p l u s a g i n g . The e r r o r s i n t r o d u c e d by t h e s e v a r i a t i o n s a r e of the same o r d e r as measurement e r r o r s f o r the d i g i t a l systems ( d i s c u s s e d i n S e c t i o n 3.6). Clock Drift 180 185 - 190 Time (days) 195 200 F i g u r e 3.2 Clock D r i f t Curve f o r D i g i t a l U n i t 008 at PMP. Symbols i n d i c a t e times at which the d r i f t was monitored using WWV r a d i o time. The l i n e s are l i n e a r i n t e r p o l a t i o n s of the d r i f t r a t e from which a r r i v a l time c o r r e c t i o n s were made. o 41 3.5 DATA EDITING The d a t a r e c o r d e d d u r i n g t h e f i e l d e x p e r i m e n t was c o n t a i n e d on 83 d i g i t a l c a s s e t t e s and 38 a n a l o g t a p e s i . e . a b o u t 13,600 s t a t i o n r e c o r d s i n d i g i t a l form and 190 s t a t i o n d a y s of c o n t i n u o u s a n a l o g r e c o r d i n g . T h i s p r e s e n t e d a f o r m i d a b l e d a t a h a n d l i n g p r o b l e m and r e q u i r e d s i g n i f i c a n t programming, p a r t i c u l a r l y s i n c e i t was t h e f i r s t e x p e r i m e n t w i t h t h e d i g i t a l s y s t e m s . As t h e i n n e r network c o n s i s t e d l a r g e l y o f MCR-600 u n i t s and due t o t h e r e l a t i v e e a s e i n d a t a h a n d l i n g , t h e d i g i t a l d a t a was p r o c e s s e d f i r s t . The c a s s e t t e s f o r e a c h s t a t i o n were s e q u e n t i a l l y t r a n s f e r r e d o n t o s t a n d a r d 9 t r a c k d i g i t a l t a p e . The 21 b y t e r e c o r d h e a d e r s w h i c h c o n t a i n t h e r e c o r d s t a r t t i m e s were t h e n s t r i p p e d i n t o a computer w o r k i n g f i l e . T h i s a l l o w e d a s e a r c h between s i t e s f o r c o i n c i d e n t e v e n t s ( i . e . t h o s e whose r e c o r d s t a r t t i m e s were w i t h i n 5 s e c o n d s of e a c h o t h e r ) and s u b s e q u e n t r e g r o u p i n g o f t h e r e c o r d s o n t o a t a p e by e v e n t r a t h e r t h a n s t a t i o n , w i t h o n l y t h e f i r s t 8 s e c o n d r e c o r d o f e a c h e v e n t r e t a i n e d . S i n c e 4 o b s e r v a t i o n s a r e needed t o l o c a t e an e v e n t and t h e a n a l o g s t a t i o n s were g e n e r a l l y on t h e p e r i p h e r y of t h e a r r a y , o n l y t h e 366 e v e n t s r e c o r d e d on 4 o r more d i g i t a l s e i s m o g r a p h s were u s e d i n t h e a n a l y s i s . T h e s e e v e n t s have been d i g i t a l l y p l o t t e d . The e s t i m a t e d t i m e t o f i n d and t h e n p l a y back t h e s e e v e n t s from t h e a n a l o g t a p e s i s a b o u t 200 h o u r s w i t h c o m p a r a b l e t i m e r e q u i r e d f o r b a s i c a n a l y s i s . T h e r e f o r e , o n l y c r i t i c a l l y l o c a t e d a n a l o g s t a t i o n s have been p l a y e d o n t o c h a r t r e c o r d s . S t a t i o n P I T ( s e e F i g u r e 1.2 p 10.) was i n i t i a l l y p l a y e d back due t o i t s 42 c r i t i c a l l o c a t i o n a t t h e s o u t h e r n end o f t h e i n n e r n e t . I t was a p a r t i c u l a r l y i m p o r t a n t s o u t h e r l y c o n s t r a i n t as t h e NCN d i g i t a l s t a t i o n was m a l f u n c t i o n i n g f o r most o f t h e e x p e r i m e n t . S t a t i o n MRK was r e q u i r e d as a w e s t e r l y c o n s t r a i n t , t h e n SUL was a l s o p l a y e d back f o r a b o u t a t h i r d o f t h e e v e n t s i n o r d e r t o show t h a t h y p o c e n t r e l o c a t i o n s would n o t be moved s i g n i f i c a n t l y by a d d i t i o n of a f u r t h e r a r r i v a l t i m e . I t a l s o p r o v i d e d a n o r t h e r l y c o n s t r a i n t f o r t h o s e e v e n t s l o c a t i n g i n t h e v i c i n i t y o f , and b e y o n d , D27. The e f f e c t o f s t a t i o n c o n s t r a i n t on e v e n t l o c a t i o n s w i l l be f u r t h e r d i s c u s s e d i n l a t e r c h a p t e r s . F i g u r e 3.3 i s an example of t h e d a t a a v a i l a b l e f o r one e v e n t w h i c h shows 7 d i g i t a l and 3 a n a l o g r e c o r d s . As e x p e c t e d , a r r i v a l s r e c o r d e d on t h e a n a l o g s y stems c o n t a i n l o w e r f r e q u e n c e s . P r e l i m i n a r y a n a l y s i s o f t h e d a t a i n v o l v e d ( i ) p i c k i n g and r e a d i n g P-wave a r r i v a l t i m e s , and S where p o s s i b l e ( i i ) m a king c l o c k d r i f t c o r r e c t i o n s t o t h o s e a r r i v a l t i m e s a t d i g i t a l s t a t i o n s ( i i i ) d e t e r m i n i n g t h e f i r s t m o t i o n o f t h e P-waves. EVENT(7) : 2 SITE 1 169 19:07:34.65 DY=800 10 S O 35.0 37.0 30.0 30.0 4O.0 41.0 42.0 O.O 44.0 • 1 1 1 ' 1 1—-> 1 1 1 ' 1 1 1 1 J  SITE 3 169 19:07:34.08 DY=400 1.0 33.0 3S.0 37.0 30.0 30.0 40.0 41.0 42.0 43.0 44.0 I I I I I I I 1 1 1 1 1 1 1 1 SITE 4 169 19:07:33.80 DY=800 1.8 34,0 39.0 98.0 97.0 90.0 30.0 4D.0 41.0 43.0 49.0 I I I t 1 1 I 1 1 1 1 1 1 1 1 1 1 1 1 1 PMP SITE 5 169 19:07:34.07 0T=800 1.0 35.0 30.0 37.0 30.0 30.0 40.0 41.0 42.0 43.0 44.0 I I I 1 1 1 1 1 i I 1 I I • • I I I I I SITE 6 169 19:07:32.88 DY=500 X2.0 33.0 34.0 35.0 36.0 37.0 30.0 30.0 40.0 41.0 42 I ' 1 1 J 1 1 1 1 ' ' 1 1 1 1 S I T E 8 4p SUL i »•< . S I T E 10 40 F i g u r e 3.3 T y p i c a l Event recorded by 7 d i g i t a l and 3 analog s t a t i o n s . The time s c a l e i s in seconds, note that the analog r e c o r d i n g s (SUL, MRK and PIT) c o n s i s t of lower f requenc i e s . 44 3 . 6 ERRORS IN EVENT ARRIVAL TIME MEASUREMENTS D i g i t a l r e c o r d s a r e p l o t t e d a t . a s c a l e of 1" = 1 s and w i t h a 0 . 0 2 " measuring s c a l e sharp o n s e t s can be p i c k e d t o 0 .01 s or b e t t e r i . e . a p p r o a c h i n g the sample i n t e r v a l of At = 0 . 0 0 6 6 s. In the case of l e s s s h a r p , but s t i l l good, a r r i v a l s the e r r o r band c o u l d be as l a r g e as 0 . 0 2 0 t o 0 . 0 3 0 s, t h a t . i s ± U .015 s. Another s o u r c e of e r r o r a r o s e from a paper s t r e t c h of 0 . 3 % and as most e v e n t s occur i n the f i r s t 3 seconds of the p l o t t h e r e i s an e r r o r of 0 . 0 0 t o 0 . 0 1 s or ± 0 . 0 0 5 s. Coupled w i t h the e r r o r due t o the n a t u r e of the c r y s t a l c l o c k s as d i s c u s s e d e a r l i e r , the t o t a l e r r o r i n a r r i v a l time f o r good d i g i t a l r e c o r d s i s ± 0 . 0 3 s. Analog r e c o r d s a r e p l a y e d back a t 4 mm = 1 s and u s i n g the 0 . 0 1 6 " s c a l e and a m a g n i f y i n g g l a s s on the a n a l o g r e c o r d s , the r e a d i n g e r r o r , or h a l f the s m a l l e s t measuring u n i t i s , ± 0 . 0 1 s. C h a r t pen t h i c k n e s s of 0.0-1 s made i t i m p o s s i b l e t o p i c k sharp a r r i v a l s and time c h a n n e l d e f l e c t i o n s t o b e t t e r than t h i s . Another s o u r c e of e r r o r was due t o p o s s i b l e pen m i s a l i g n m e n t , between c h a n n e l s . These f a c t o r s l e a d t o a t o t a l a r r i v a l time e r r o r of about ± 0 . 0 3 s which i s s i m i l a r t o t h a t f o r the d i g i t a l a r r i v a l s . We note t h a t 0 . 0 3 s c o r r e s p o n d s t o a P-wave p r o p a g a t i o n d i s t a n c e of 160 m ( 5 0 0 ' ) assuming a v e l o c i t y of 5 . 3 kms - 1. E r r o r s i n the a r r i v a l t i m e s f o r S-waves tended t o be h i g h e r due t o the d i f f i c u l t y i n s e e i n g t h e i r f i r s t a r r i v a l , o f t e n b u r i e d i n the P-waves coda. 45 3.7 INSTRUMENT POLARITIES Instrument p o l a r i t i e s were cal i b r a t e d using the test blasts and other large mine explosions. As expected, a positive p o l a r i t y or compressional f i r s t a r r i v a l was generally observed at each station with the exception of the two underground stations, D39 and D27. They recorded negative p o l a r i t i e s in the cases when they were located below the l e v e l of the explosion; that i s since the cavity containing the seismometer i s small with respect to the P-wavelength (discussed in Chapter 5) the whole cavity and seismometer have an i n i t i a l displacement downwards. 46 CHAPTER 4: VELOCITY MODEL FOR THE SULLIVAN MINE AREA In t h i s c h a p t e r t h e b a s i s o f a u n i f o r m v e l o c i t y model f o r th e S u l l i v a n Mine a r e a i s a n a l y s e d and t h e s u i t a b i l i t y o f t h e model f o r use i n t h e h y p o c e n t r e l o c a t i o n p r o g r a m i s j u s t i f i e d . A s a f e g u a r d a g a i n s t e r r o r t h a t may be i n t r o d u c e d due t o g e o l o g i c s t r u c t u r e i s d i s c u s s e d i n t e r m s o f a s t a t i o n w e i g h t i n g f a c t o r ; and t h e p o s s i b l e e f f e c t o f mine w o r k i n g s on s e i s m i c wave p r o p a g a t i o n i s e x a m i n e d . 4.1 DEVELOPMENT OF A UNIFORM MODEL D u r i n g t h e . p e r i o d of t h e e x p e r i m e n t , f o u r t e s t e x p l o s i o n s were u s e d t o o b t a i n a v e l o c i t y model f o r t h e S u l l i v a n M i n e a r e a . T1: June 20, 1980 Open P i t b l a s t (4475, 8120, 4485) 1 r e c o r d e d a t 9 s t a t i o n s ( F i g u r e 4 . 1 ) . T2: J u l y 3, 1980 Open P i t b l a s t (4360, 8140, 4485) r e c o r d e d a t 8 s t a t i o n s ( F i g u r e 4 . 2 ) . T3 & T4: J u l y 8, 1980 Two t i m e d b l a s t s a t #10 p i t (-3550, 9900, 4587), t h e f i r s t b e i n g r e c o r d e d by 9 s t a t i o n s and t h e s e c o n d by 8. As t h e l o c a t i o n was t h e same f o r b o t h #10 p i t b l a s t s , and t h e o r i g i n t i m e known, b o t h were p l o t t e d on t h e same t r a v e l t i m e d i a g r a m ( F i g u r e 4 . 3 ) . O n l y t h e l o c a t i o n , and not t h e o r i g i n t i m e , i s known a c c u r a t e l y f o r t h e open p i t b l a s t s . Distance (km) F i g u r e 4.1 T r a v e l - T i m e D i a g r a m f o r t h e J u n e 20, 1980 Open P i t B l a s t . The t i m e i n t e r c e p t i s unknown but was a r b i t r a r i l y s e t t o z e r o a s t h e ^ e x p l o s i o n was i n s o l i d r o c k . The h e i g h t of t h e s y m b o l s i n d i c a t e t h e - j p r o b a b l e e r r o r o r u n c e r t a i n t y i n t h e a r r i v a l t i m e . Distance (km) F i g u r e 4.2 T r a v e l - T i m e D i a g r a m f o r t h e J u l y 3, 1980 Open P i t B l a s t . ^ The t i m e i n t e r c e p t i s unknown but was a r b i t r a r i l y s e t t o z e r o as t h e co e x p l o s i o n was i n s o l i d r o c k . The h e i g h t o f t h e s y m b o l s i n d i c a t e t h e p r o b a b l e e r r o r o r u n c e r t a i n t y i n t h e a r r i v a l t i m e d a t a . T3 & T4: #10 Pi t <M_ 0.0 1.0 2.0 3.0 4.0 5.0 Distance (km) F i g u r e 4.3 T r a v e l - T i m e D i a g r a m f o r t h e J u l y 8, 1980 Number 10 P i t B l a s t s . The b l a s t s were m o n i t o r e d so t h e o r i g i n t i m e i s known e x a c t l y . The h e i g h t of t h e s y m b o l s i n d i c a t e t h e p r o b a b l e e r r o r o r u n c e r t a i n t y i n t h e d a t a . 50 We w i l l assume f o r s i m p l i c i t y t h a t i n t h e f o l l o w i n g a n a l y s e s we can a s c r i b e t h e u n c e r t a i n t y of t h e measurement t o t a l l y t o t h e d e p e n d e n t p a r a m e t e r ( t r a v e l t i m e ) . "This i s a v a l i d a s s u m p t i o n as t h e i n s t r u m e n t a l and r e a d i n g e r r o r i n t h e a r r i v a l t i m e c a l c u l a t i o n i s a b o u t an o r d e r o f m a g n i t u d e more t h a n t h e e r r o r i n s t a t i o n and t e s t e x p l o s i o n l o c a t i o n s . T h a t i s 50' o r 0.0028 s e r r o r i n s t a t i o n l o c a t i o n compared w i t h 0.030 s, t h e t o t a l a r r i v a l t i m e e r r o r . A s t a n d a r d l e a s t - s q u a r e s a p p r o a c h was u s e d t o f i t a s t r a i g h t l i n e t o t h e d a t a p o i n t s i n t h e t i m e - d i s t a n c e g r a p h s . The v e l o c i t y , t i m e - i n t e r c e p t and p r o b a b l e e r r o r of t h e d a t a p o i n t s were d e t e r m i n e d u s i n g s t a n d a r d p r o c e d u r e s ( B e v i n g t o n , 1969). F i g u r e s 4.1, 4.2 and 4.. 3 show t h e t r a v e l t i m e d-iagrams f o r t h e f o u r t e s t e x p l o s i o n s and t h e r e s u l t s o f t h e l e a s t s q u a r e s f i t . A t i m e i n t e r c e p t o f 0.034 s was f o u n d f o r t h e #10 p i t e x p l o s i o n s , a s t h e y were l o c a t e d i n an a r e a o f p o o r l y s o r t e d , u n c o n s o l i d a t e d g l a c i a l m a t e r i a l . A s s u m i n g a r e a s o n a b l e v e l o c i t y f o r t h e g l a c i a l m a t e r i a l of v 0 = 1.5 t o 1.8 kms" 1 o v e r l y i n g s o l i d r o c k w i t h v, = 5.3 kms" 1, t h e n i t s t h i c k n e s s c a n be e a s i l y c a l c u l a t e d a s f o l l o w s ; z = _Li . V Q v. 2 / v , 2 - v 0 2 = 27 m t o 33 m Thus t h e g l a c i a l d e b r i s e x t e n d s t o a d e p t h of a b o u t 30 m (100 f t ) , a s s u m i n g t h e s i m p l e t w o - l a y e r c a s e d e s c r i b e d above i s v a l i d . The t i m e i n t e r c e p t s f o r t h e open p i t e x p l o s i o n s were a r b i t r a r i l y s e t t o z e r o , and t h a t p o i n t t a k e n t o be t h e o r i g i n t i m e as b o t h open p i t b l a s t s o c c u r r e d i n s o l i d r o c k . 51 An i n d e p e n d e n t e s t i m a t e o f t h e e r r o r i n t h e d a t a c a n be d e t e r m i n e d from t h e d a t a i t s e l f b y i t s own s c a t t e r ( B e v i n g t o n , 1969). T h a t i s , i f we assume t h a t t h e u n c e r t a i n t i e s a r e a l l i n s t r u m e n t a l , hence t h e s t a n d a r d d e v i a t i o n f o r a l l d a t a p o i n t s a r e e q u a l , t h e n we can e s t i m a t e them from t h e d a t a . The u n c e r t a i n t y o r s t a n d a r d d e v i a t i o n o f t h e a r r i v a l t i m e d a t a i s I n d i c a t e d i n F i g u r e s 4.1, 4.2 & 4.3 by t h e s i z e o f t h e d a t a p o i n t s y m b o l . The t o t a l h e i g h t o f e a c h symbol i s e q u a l t o t w i c e t h e p r o b a b l e e r r o r (where P.E. e q u a l s 2/3 t h e s t a n d a r d d e v i a t i o n ) t o i n d i c a t e t h a t t h e t r u e a r r i v a l t i m e v a l u e l i e s w i t h i n p l u s o r minus t h e P.E. w i t h a p r o b a b i l i t y of 50%. T h i s f i g u r e (± 0.01 t o ± 0.02 s from F i g u r e s 4.1, 4.2 & 4.3) w i l l o n l y be a r o u g h e s t i m a t e o f t h e t r u e e r r o r i n d a t a a s t h e s t a n d a r d d e v i a t i o n s f o r t h e d a t a p o i n t s a r e i n r e a l i t y n o t e q u a l . S i n c e a u n i f o r m v e l o c i t y model has been c h o s e n f o r t h e r e g i o n , p a r t of t h e p r o b a b l e e r r o r f o r e a c h p o i n t t h a t we have assumed t o be i n s t r u m e n t a l w i l l i n f a c t be due t o v a r i a t i o n s i n t h e g e o l o g i c s t r u c t u r e . A mean r e g i o n a l v e l o c i t y f o r t h e S u l l i v a n M i n e a r e a was c a l c u l a t e d a s a w e i g h t e d a v e r a g e ( B e v i n g t o n , 1969). The s l o p e of t h e l i n e ak , d e t e r m i n e d f o r e a c h t e s t e v e n t , i s w e i g h t e d by t h e i n v e r s e o f i t s own v a r i a n c e * a i i n t h e sum. a' = 0.1886 km" 1s c = 1/a' = 5.30 kms* 1 The mean s l o p e has a v a r i a n c e g i v e n by, E(1 A = 0.0025 52 so we have a P-wave v e l o c i t y , o = 5.30 ± 0.07 kms" 1 U n f o r t u n a t e l y an S-phase was e i t h e r a b s e n t or v e r y d i f f i c u l t t o o b s e r v e on t h e t e s t e x p l o s i o n r e c o r d s , as i s e x p e c t e d f o r an e x p l o s i v e s o u r c e . T h e r e f o r e t h e r e l a t i o n s h i p p = c//3~, c o r r e s p o n d i n g t o a P o i s s o n ' s r a t i o o f 0.25, was u s e d y i e l d i n g an S-wave v e l o c i t y , p , o f 3.06 kms" 1. T h i s seems a r e a s o n a b l e v a l u e t o use as a summary o f c r u s t a l P o i s s o n v a l u e s i n d i c a t e a r a n g e f r o m 0.23 t o 0.26 (Cumming e t a l , 1979). 4.2 JUSTIFICATION FOR A UNIFORM VELOCITY MODEL: DISCUSSION OF DEVIATIONS DUE TO GEOLOGIC STRUCTURE G e o l o g i c v a r i a t i o n w i l l l e a d t o a s y s t e m a t i c d e p a r t u r e o f a r r i v a l s from t h e s t r a i g h t l i n e of t h e u n i f o r m v e l o c i t y m o d e l . F o r example i n t h e c a s e of t h e #10 p i t b l a s t s . ( F i g u r e 4.~3), a r r i v a l s r e c o r d e d a t MRK, BOG and SUL a r e c o n s i s t e n t l y e a r l y w h i c h s u g g e s t s t h a t t h e t r a v e l p a t h s t o t h e s e s t a t i o n s , n o r t h of t h e K i m b e r l e y F a u l t a r e t h r o u g h s l i g h t l y h i g h e r v e l o c i t y m a t e r i a l . T r a v e l t i m e c o m p e n s a t i o n c o r r e c t i o n s may be a p p l i e d i n t h e h y p o c e n t r e l o c a t i o n p rogram, t o t h o s e p o i n t s t h a t d e p a r t from t h e s t r a i g h t l i n e by more t h a n t h e i r p r o b a b l e e r r o r , ( t h e p r o b a b l e e r r o r b e i n g c o n s i s t e n t w i t h t h e r e c o r d r e a d i n g e r r o r o f 0.01 t o 0.02 s ) . T a b l e 4.1 l i s t s t h e d e p a r t u r e o f P-wave a r r i v a l t i m e a t e a c h s t a t i o n from t h e u n i f o r m v e l o c i t y c u r v e f o r e a c h t e s t e v e n t . T h o s e t h a t d e p a r t from t h e s t r a i g h t l i n e by more t h a n t h e p r o b a b l e e r r o r a r e u n d e r l i n e d and i t w i l l be assumed t h a t s u c h d e p a r t u r e s a r e due t o r e a l g e o l o g i c a l v a r i a t i o n . 53 C a r e must be t a k e n when a t t e m p t i n g t o compensate f o r d e p a r t u r e s from t h e r e g i o n a l v e l o c i t y as d i f f e r e n t t r a v e l p a t h s t o t h e same s t a t i o n w i l l y i e l d d i f f e r e n t v e l o c i t y e s t i m a t e s . Thus f o r t h e s t a t i o n s i n t h e immediate mine a r e a , (D27, D39, SHF, P I T and NAD), where t h e e v e n t s a r e l i k e l y t o be a t v a r i o u s o r i e n t a t i o n s w i t h r e s p e c t t o t h e s t a t i o n s , a m e a n i n g f u l c o r r e c t i o n c a n n o t be a p p l i e d . T h i s i s a p p a r e n t i n T a b l e 4.1; t r a v e l t i m e c o r r e c t i o n s f o r t h e c l o s e r s t a t i o n s a r e i n c o n s i s t e n t i n s i g n and m a g n i t u d e between t h e d i f f e r e n t t e s t e v e n t l o c a t i o n s . F o r s t a t i o n s o u t s i d e t h e immediate v i c i n i t y o f t h e mine a r e a t h e t r a v e l p a t h w i l l n o t v a r y much o v e r t h e whole zone i n w h i c h t h e m a j o r i t y of e v e n t s a r e e x p e c t e d t o o c c u r and t h e c o r r e c t i o n s a r e c o n s i s t e n t between t h e d i f f e r e n t t e s t e v e n t l o c a t i o n s ( T a b l e 4 . 1 ) . S i n c e most o f t h e e v e n t s o c c u r i n t h e mine a r e a ,the m a g n i t u d e of t h e t r a v e l t i m e c o r r e c t i o n s f r o m t h e n e a r b y open p i t b l a s t s (T1 & T2) a r e more m e a n i n g f u l . The a v e r a g e c o r r e c t i o n s f o r t h e open p i t b l a s t s e x c e e d t h e p r o b a b l e e r r o r o f t h e d a t a p o i n t s i n t h r e e c a s e s ; MOR: +0.014 L O I : +0.017 MRK: -0.015 and i t i s t h e s e t h a t were t r i e d i n t h e h y p o c e n t r e l o c a t i o n p r o g r a m . F i g u r e 4.4 shows t h e l o c a t i o n of h y p o c e n t r e s f o r t e s t e v e n t s c a l c u l a t e d b o t h w i t h and w i t h o u t t r a v e l t i m e c o r r e c t i o n s . T h e r e i s a s y s t e m a t i c s h i f t i n t h e e p i c e n t r a l ( x , y ) p o s i t i o n ; 54 STATION NAME TRAVEL TIME CORRECTION ( M i l l i s e c o n d s ) T l T2 T3 T4 SHF -0.012 +0.019 +0.029 D27 -0.022 +0.037 PMP +0.012 +0.0005 -0.005 MOR +0.010 + 0 .017 +0.025 +0.019 NAD -0.009 -0.012 LOl +0.024 + 0 .010 +0.019 +0.014 SUL -0.004 -0.052 -0.038 MRK -0.015 -0.023 -0.022 BOG -0.006 -0.018 -0.033 PIT -0.005 -0.016 +0.007 + 0 .023 Table 4.1 Departure of the P-Wave a r r i v a l time at each station from the uniform v e l o c i t y curve for each test event. Those underlined depart from the straight l i n e by more than the probable error, these are i s assumed to be due to real•geological v a r i a t i o n . 55 g e n e r a l l y l e s s t h a n 80 f t e a s t e r l y o f t h e p o s i t i o n c a l c u l a t e d w i t h o u t t h e c o r r e c t i o n . T h i s i s as e x p e c t e d ; t h e c o r r e c t i o n l e n g t h e n s t h e P-wave t r a v e l t i m e f r o m an e v e n t t o MRK, t o t h e west, and s h o r t e n s t h e t i m e t o LOI and MOR, t o t h e e a s t , t h u s moving t h e c a l c u l a t e d e p i c e n t r e i n an e a s t e r l y d i r e c t i o n . The improvement i n e p i c e n t r a l l o c a t i o n i s d e b a t a b l e ; t h e c o r r e c t i o n s l e a d t o an improvement when t h e c a l c u l a t e d e p i c e n t r e i s t o t h e west o f t h e t r u e l o c a t i o n and a w o r s e n i n g , as i n t h e c a s e of T2, t h e J u l y 3 open p i t b l a s t , when t h e c a l c u l a t e d h y p o c e n t r e i s e a s t o f t h e t r u e p o s i t i o n . E ven f o r t h e s e e v e n t s w h i c h were u s e d a s t h e b a s i s f o r d e r i v i n g t h e t r a v e l t i m e c o r r e c t i o n , t h e improvement i n t h e e p i c e n t r a l l o c a t i o n was a t b e s t m a r g i n a l ; and as t h e s e p o s s i b l e c o r r e c t i o n s l i e w i t h i n t h e t o t a l a r r i v a l t i m e e r r o r range o f ± 0.03 s (as w i l l be d i s c u s s e d i n C h a p t e r 5 ) , t h e r e a p p e a r s t o be no j u s t i f i c a t i o n f o r u s i n g them. Summary ( i ) A r e g i o n a l P-wave v e l o c i t y of 5.30 k m s - 1 was d e r i v e d f r o m c a l i b r a t i o n e x p l o s i o n s f o r t h e p u r p o s e o f h y p o c e n t r e c a l c u l a t i o n ( i i ) A r e g i o n a l S-wave v e l o c i t y o f 3.06 k m s - 1 was d e t e r m i n e d u s i n g a P o i s s o n ' s r a t i o o f 0.25 ( i i i ) The u n i f o r m r e g i o n a l model was u s e d i n t h e h y p o c e n t r e l o c a t i o n p r o gram; s y s t e m a t i c t r a v e l t i m e c o r r e c t i o n s were n o t a p p l i e d a s t h e y d i d n o t l e a d t o a s i g n i f i c a n t improvement i n e v e n t l o c a t i o n . Test Event Locations lO-I m -OOOtT 00S2T • MRK 4> PMP ) . ' i \ \ i / / • \ \ i i LOI • o o o -o o_ cn lfc T3&4 (#10 PIT BLASTS) / t i / / I / i j r 1 s. —« N -1 \ / / 1 1 \ 4> D39 / i / i / / / / / / oooe L o c a t i o n o f T e s t E v e n t s \ \ P1 T 4 ;. ^ T l &2 (OPEN PIT NAD BLASTS) 0059 C a l c u l a t e d E p i c e n t r e s o o C a l c u l a t e d E p i c e n t r e s w i t h T r a v e l Time C o r r e c t i o n s ° -4500 -3000 -1500 0 1500 3000 4500 6000 7500 9000 F i g u r e 4.4 L o c a t i o n of t h e c a l i b r a t i o n e v e n t s T l , T 2 , T3 and T4 and t h e i r c a l c u l a t e d e p i c e n t r e s . The c a l c u l a t i o n s were done b o t h w i t h and w i t h o u t t r a v e l t i m e c o r r e c t i o n s . 57 4.3 THE STATION WEIGHTING FACTOR A w e i g h t i n g f a c t o r , WF = A B + .<H , where A = 10000 B = 600 and d; i s t h e d i s t a n c e i n m e t r e s from t h e s o u r c e t o t h e d e t e c t i n g s t a t i o n , was a p p l i e d t o t h e S u l l i v a n Mine a r r a y . C o n s t a n t s A and B a r e a r b i t a r y and i n t h i s c a s e were c h o s e n t o be t h e t h e same as t h o s e u s e d by S p o t t i s w o o d e (1980) a t t h e E a s t Rand P r o p r i e t a r y M i n e . F o r example, C o n s i d e r as an example, an e v e n t o c c u r r i n g i n t h e open p i t : The c l o s e s t s t a t i o n s SHF, NAD and PIT have t h e h i g h e s t w e i g h t i n g w h i c h i s a b o u t 4 t i m e s th e w e i g h t i n g g i v e n t o MRK, t-he f u r t h e s t . s t a t i o n i n t h e i n n e r n e t , and 7 t i m e s t h a t g i v e n t o MAT and BOG, t h e most d i s t a n t o u t e r n e t s t a t i o n s . The w e i g h t i n g assumes t h a t e r r o r s i n t h e a r r i v a l s a t t h e more d i s t a n t s t a t i o n s a r e l i k e l y t o be h i g h e r ; t h e two r e a s o n s f o r t h i s a r e : ( i ) s e i s m i c waves t r a v e l l i n g l o n g e r d i s t a n c e s t h r o u g h t h e e a r t h would, be more a f f e c t e d by d e p a r t u r e s f r o m t h e assumed u n i f o r m v e l o c i t y m o d e l . ( i i ) a t t e n u a t i o n o f t h e h i g h e r f r e q u e n c i e s a t t h i s d i s t a n c e w i l l l e a d t o l e s s s h a r p f i r s t a r r i v a l s and t h u s l e s s r e l i a b l e a r r i v a l t i m e p i c k s . 58 4.4 EFFECT OF THE MINE WORKINGS ON THE MODEL I n t u i t i v e l y i t i s e x p e c t e d t h a t i f t h e w a v e l e n g t h s a r e l o n g compared t o t h e s i z e of t h e c a v i t y , t h e c a v i t y w i l l have l i t t l e • e f f e c t . The c a l c u l a t i o n s o f G r e e n f i e l d (1977) show t h a t a t h i g h e r f r e q u e n c i e s a c a v i t y w i l l d i s t o r t t h e r a d i a t i o n p a t t e r n t o t h e e x t e n t t h a t i t would make t h o s e f r e q u e n c i e s u n o b s e r v a b l e i n some d i r e c t i o n s . An o p e n i n g i s shown t o e f f e c t w a v e l e n g t h s s h o r t e r t h a n a p p r o x i m a t e l y 15 c a v i t y r a d i i ( G r e e n f i e l d , 1977). In t h e c a s e of t h e S u l l i v a n Mine we have; v = 5.3 kms" 1 f = 10 - 20 Hz now v = f x so X = 260 - 530 m T h a t i s , a c a v i t y of r a d i u s 17-30 m would be n e c e s s a r y t o a f f e c t t h e wave p r o p a g a t i o n . A l l t h e S u l l i v a n Mine t u n n e l s ( r a d i u s 1-2 m) and a l l e x c e p t t h e l a r g e s t s t o p e s a r e s m a l l e r t h a n t h i s ; t h u s t h e m a j o r i t y of mine w o r k i n g s do n o t s i g n i f i c a n t l y e f f e c t t h e wave p r o p a g a t i o n . The l a r g e s t s t o p e s have d i m e n s i o n s o f a p p r o x i m a t e l y 50 m by 70 m by 100 m h i g h (P. Ransom, p e r s o n a l c o m m u n i c a t i o n , 1982) w h i c h a r e l a r g e enough t o a f f e c t t h e wave p r o p a g a t i o n from c e r t a i n d i r e c t i o n s . None o f t h e s t a t i o n s i n t h e i n n e r n e t show e v i d e n c e o f b e i n g c o n s i s t e n t l y s h i e l d e d f r o m wave r a d i a t i o n . However wave a m p l i t u d e s , p a r t i c u l a r l y t h o s e of t h e h i g h e r f r e q u e n c y components, may be l o w e r e d by t h e p r e s e n c e o f t h e s e l a r g e s t o p e s d e p e n d i n g on t h e s t o p e , s o u r c e a n d r e c e i v e r g eometry ( G r e e n f i e l d , 1977). T h i s a s p e c t w i l l n o t be d e a l t w i t h any f u r t h e r i n t h e p r e s e n t s t u d y . P-wave v e l o c i t y t y p i c a l P-wave f r e q u e n c i e s where X i s t h e w a v e l e n g t h 59 CHAPTER 5: DATA SET CHARACTERISTICS 5.1 EVENT CLASSIFICATION: F i g u r e 5.1 shows t h e breakdown o f a l l 1551 e v e n t s r e c o r d e d on 2 o r more d i g i t a l s e i s m o g r a p h s d u r i n g t h e e x p e r i m e n t . E v e n t s r e c o r d e d by 4 o r more s t a t i o n s , h e n c e u s e d i n t h e a n a l y s i s , a r e d i v i d e d i n t o major o b s e r v a b l e t y p e s . An e v e n t was c l a s s i f i e d a c c o r d i n g t o i t ' s coda shape, f r e q u e n c y c o n t e n t , phase s e p a r a t i o n and t i m e o f o c c u r r e n c e . The d i f f e r e n t t y p e s a r e as f o l l o w s : ( i ) Emergent E v e n t s A t y p i c a l example i s seen i n F i g u r e 5.2. The s i g n a l emerges s l o w l y from t h e b a c k g r o u n d n o i s e , t a k i n g on a v e r a g e between 1 and 2 s e c o n d s t o r e a c h a maximum a m p l i t u d e , t h e n d e c a y s t o b a c k g r o u n d l e v e l p r o d u c i n g a c h a r a c t e r i s t i c diamond sh a p e d c o d a . The e v e n t d u r a t i o n i s no l o n g e r t h a n a b o u t 5 s e c o n d s . S i g n a l f r e q u e n c i e s ( d e t e r m i n e d f r o m a r r i v a l s a t LOI) a r e commonly i n t h e ra n g e from 8 t o 10 Hz w i t h some r e a c h i n g 12 Hz; w h i c h i s i n g e n e r a l l o w e r t h a n t h a t o b s e r v e d i n t h e o t h e r e v e n t t y p e s . T h e i r emergent o n s e t s and l o w e r f r e q u e n c y c o n t e n t i n d i c a t e t h a t t h e y a r e n o t t h e r e s u l t o f an a b r u p t e n e r g y r e l e a s e as would be e x p e c t e d f o r an e x p l o s i o n o r sudden r u p t u r e i n v i r g i n or t i g h t l y l o c k e d r o c k . I n s t e a d t h e s e e v e n t s r e p r e s e n t a more g r a d u a l r e l e a s e of e n e r g y . The u n c e r t a i n t y i n t h e f i r s t a r r i v a l 60 ALL EVENTS RECORDED 366 EVENTS USED U S E D F i g u r e 5.1 E v e n t C l a s s i f i c a t i o n . E v e n t s r e c o r d e d by 4 o r more s t a t i o n s a r e shown d i v i d e d i n t o m a j o r o b s e r v a b l e t y p e s . The " o t h e r " g r o u p i s t h e most i m p o r t a n t and c o n s i s t s o f an unknown c o m b i n a t i o n of e x p l o s i o n and m i c r o e a r t h q u a k e e v e n t s o f w h i c h t h e "weekend" e v e n t s f o r m a b a s i c a l l y e x p l o s i o n f r e e s u b s e t . SITE 4 184 10:12:35.89 DY=500 F i g u r e 5.2 Example o f a S e i s m i c E v e n t w i t h an Emergent F i r s t A r r i v a l . The bounds of a p l a u s i b l e f i r s t a r r i v a l p i c k a r e i n d i c a t e d by t r i a n g l e s . E v e n t s o f t h i s n a t u r e a r e n o t u s e f u l i n our a p p l i c a t i o n due t o l a r g e l o c a t i o n e r r o r s . 62 t i m e p i c k s i s e x t r e m e l y h i g h , as i n d i c a t e d by t h e t r i a n g l e s on F i g u r e 5.2. The 0.2 s e c o n d s shown h e r e c o r r e s p o n d s t o a P-wave t r a v e l l i n g i n e x c e s s of 1 km so c l e a r l y t h i s t y p e of e v e n t c a n n o t be l o c a t e d a c c u r a t e l y . Emergent e v e n t s c o n s t i t u t e a b o u t 1/3 o f t h e d a t a s e t or 118 e v e n t s as shown i n F i g u r e 5.1, and o f t h e s e a b o u t 1/2 were d i s c a r d e d b e c a u s e o f t h e e x t r e m e e r r o r i n p i c k i n g f i r s t a r r i v a l s ; an a t t e m p t was made t o l o c a t e t h e r e m a i n i n g 60 e v e n t s . ( i i ) M u l t i p l e B l a s t s and E x p l o s i o n E v e n t s M u l t i p l e b l a s t s a r e d i s t i n c t l y c h a r a c t e r i z e d by e n e r g y b u r s t s t h r o u g h o u t t h e s e i s m o g r a m as shown i n F i g u r e 5.3. T h i s complex c o d a shape has been a t t r i b u t e d t o t h e l o n g d e l a y f i r i n g s e q u e n c e s t h a t a r e u s e d i n o r e e x t r a c t i o n b l a s t i n g . The o t h e r e x p l o s i o n e v e n t s were d i s t i n g u i s h e d p r i m a r i l y by t h e i r t i m i n g . L a r g e a m p l i t u d e e v e n t s o b s e r v e d a t t h e end o f mine work s h i f t s were c l e a r l y " s h i f t change b l a s t s " and o t h e r s were d e t e r m i n e d by t h e i r c o r r e s p o n d e n c e w i t h t h e t i m e s on a l i s t of mine e x p l o s i o n s p r o v i d e d by Cominco. The E x p l o s i o n e v e n t s show f r o n t - e n d l o a d e d c o d a s , t h a t i s maximum a m p l i t u d e s w i t h i n t h e f i r s t few c y c l e s of t h e waveform, and t e n d t o have f r e q u e n c i e s i n t h e r a n g e f r o m 13 t o 16 Hz ( b a s e d on a r r i v a l s a t LOI) w i t h some o f t h e s m a l l e r e v e n t s c o n t a i n i n g f r e q u e n c i e s as low as 9 Hz. I t i s i n t e r e s t i n g t o n o t e t h e h i g h e r r e c o r d e d f r e q u e n c i e s ( 17 t o 20 Hz ) a t s i t e s D27 and NAD due. t o t h e i r p r o x i m i t y t o t h e mine w o r k i n g s . F i g u r e 5.4 i s a t y p i c a l example o f an e x p l o s i o n e v e n t . As shown i n F i g u r e 5.1 known m u l t i p l e b l a s t s and e x p l o s i o n SITE 2 170 0 . 2 : 0 5 : 1 7 . 7 2 DY = 400 17.0 18.0 19.0 20.0 21.0 22.0 23.0 2 4 , 0 25.0 26.0 27 0 F i g u r e 5.3 Example of a M u l t i p l e E vent. The onset of energy b u r s t s a r e i n d i c a t e d by t r i a n g l e s . E vents of t h i s type a r e a t t r i b u t e d t o a c o m p l i c a t e d b l a s t i n g sequence. T h i s p a r t i c u l a r event took p l a c e on Monday June 23, 1980 a t 6:09 am i n t h e #1 s u r f a c e ramp development a r e a . cr. SITE 7 .172 2 3 : 4 7 : 0 0 . 6 5 DY=80 F i g u r e 5.4 Example o f a E x p l o s i o n E v e n t . T h i s p a r t i c u l a r e x p l o s i o n t o o k p l a c e on F r i d a y J u n e 20, 1980 a t 5:45 pm i n t h e L-11-30 w o r k i n g a r e a . 65 e v e n t s make up 22% o f t h e d a t a s e t . A l t h o u g h not of d i r e c t i n t e r e s t t o t h i s s t u d y , t h e m a j o r i t y of t h e s e e v e n t s were r e t a i n e d t o s e r v e as a c o n t r o l on h y p o c e n t r e l o c a t i o n a c c u r a c y . ( i i i ) D i s t a n t E v e n t s A l t h o u g h v e r y few i n number, e v e n t s o f t h i s t y p e were r e c o g n i z a b l e by t h e c l e a r s e p a r a t i o n of t h e P and S p h a s e s . The S wave t o P wave t r a v e l t i m e d i f f e r e n c e c an be w r i t t e n i n t e r m s of t h e P and S wave v e l o c i t i e s , a s s u m i n g p r o p a g a t i o n . t h r o u g h homogeneous m a t e r i a l : t s - t P = t 4 _ p x - x = t s . p x = h y p o c e n t r a l d i s t a n c e fi = 3.06 k m s - 1 S-wave v e l o c i t y o = 5.30 kms" 1 P-wave v e l o c i t y x = 7.24 t s . p km T h e r e f o r e i f t s _ p i s g r e a t e r t h a n 1.5 s, t h e e p i c e n t r e i s l i k e l y t o be o u t s i d e t h e a r r a y . F i g u r e 5.5 shows an e v e n t w i t h t^.p = 2.5 s w h i c h i s c l e a r l y n o t o f i n t e r e s t i n t h i s e x p e r i m e n t . ( i v ) E v e n t s of I n t e r e s t The r e m a i n i n g 46% o f t h e e v e n t s u s e d , o r " o t h e r " e v e n t s as i n d i c a t e d i n F i g u r e 5.1, c o n s i s t o f mine e x p l o s i o n s as w e l l as t h e m i c r o e a r t h q u a k e e v e n t s of i n t e r e s t . F u r t h e r d i v i s i o n may be c a r r i e d o u t on a t e m p o r a l b a s i s : (a) "Weekend" E v e n t s By s e l e c t i o n of t h o s e e v e n t s t h a t o c c u r on weekends we can where t h e n F i g u r e 5.5 Example of a " L o c a l " S e i s m i c Event o u t s i d e our Region of I n t e r e s t . The S phase a r r i v a l i s chosen by a n a l y s i n g a r r i v a l s a t a l l s t a t i o n s , the S-P a r r i v a l time d i f f e r e n c e of 2.5 s i n d i c a t e s an e p i c e n t r a l d i s t a n c e of about 20 km. 67 be r e a s o n a b l y w e l l a s s u r e d of an e x p l o s i o n f r e e s u b s e t ; 47 e v e n t s o c c u r a t t h i s t i m e . The weekend e v e n t s have a s i m p l e c o d a shape, t h e e n e r g y i s f r o n t - e n d l o a d e d d e c a y i n g t o b a c k g r o u n d i n 3 t o 4 s e c o n d s . They r a n g e i n f r e q u e n c y from 10 t o 18 Hz, w i t h a p r e d o m i n a n t number o f e v e n t s a r o u n d 13 t o 14 Hz. T h i s encompasses t h e r a n g e shown by t h e e x p l o s i o n e v e n t s . O c c a s i o n a l l y a s m a l l s e p a r a t i o n between S and P p h a s e s i s e v i d e n t on some o f t h e r e c o r d s . F i g u r e 5.6 shows a t y p i c a l weekend e v e n t . (b) "Weekday" E v e n t s F o l l o w i n g s e p a r a t i o n o f t h e above m e n t i o n e d e v e n t t y p e s we a r e l e f t w i t h 120 "weekday" e v e n t s ( F i g u r e 5 . 1 ) . The e v e n t s i n t h i s g r o u p a r e s h a r p and t h u s w e l l l o c a t a b l e but s t i l l c o n s i s t of mine e x p l o s i o n s a s - w e l l as m i c r o e a r t h q u a k e e v e n t s . The s i m i l a r i t y between t h e c h a r a c t e r of t h e s e and e x p l o s i o n e v e n t s makes t h e i r s e p a r a t i o n v e r y d i f f i c u l t . Thus we would l i k e t o be a b l e t o d e t e r m i n e someform of d i s c r i m i n a t i o n c r i t e r i o n i n o r d e r t o i n c r e a s e t h e u s e f u l w o r k i n g s e t of m i c r o e a r t h q u a k e e v e n t s . SITE 4 194 05-01=01.93 DY=400 0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10 0 i \ J I I I I I I L I I I I I I l l l 1 I i F i g u r e 5.6 Example of a T y p i c a l Weekend E v e n t . A s m a l l S-P phase s e p a r a t i o n i s v i s i b l e i n t h i s c a s e . T h i s p a r t i c u l a r e v e n t o c c u r r e d 21 m i n u t e s a f t e r t h e J u l y 11, 1980 p i l l a r b l a s t and was s e e m i n g l y t r i g g e r e d by t h e l a r g e b l a s t . oo 69 5.2 EXPLOSION-MICROEARTHQUAKE DISCRIMINATION PROBLEMS When c o n s i d e r i n g a s p h e r i c a l e x p l o s i o n i n a homogeneous e l a s t i c medium compared t o a r u p t u r e a l o n g a f a u l t p l a n e o f f i n i t e s i z e , one would e x p e c t t o see t h e f o l l o w i n g d i f f e r e n c e s : (a) The e x p l o s i o n , i n v o l v i n g an e x t r e m e l y r a p i d e n e r g y r e l e a s e a t a s i n g l e p o i n t i n t h e medium, would show a h i g h e r f r e q u e n c y c o n t e n t compared t o t h e l o w e r f r e q u e n c i e s i n v o l v e d i n a r u p t u r e p r o p a g a t i n g a l o n g a f i n i t e l e n g t h s l i p s u r f a c e and o c c u r r i n g o v e r a much l o n g e r t i m e p e r i o d . (b) The e x p l o s i o n mechanism w o u l d n o t g e n e r a t e any s h e a r waves and hence i s c h a r a c t e r i z e d by a s i m p l e f r o n t l o a d e d c o d a ; t h e r u p t u r e w o u l d g e n e r a t e b o t h P and S p h a s e s w h i c h p r o p a g a t e a t d i f f e r e n t v e l o c i t i e s and t h u s p r o d u c e a more complex c o d a . ( c ) The e x p l o s i o n mechanism would g e n e r a t e a s p h e r i c a l l y s p r e a d i n g c o m p r e s s i o n wave whereas i n t h e c a s e of t h e r u p t u r e e v e n t , t h e r e c o r d i n g s t a t i o n s may e x p e r i e n c e e i t h e r a c o m p r e s s i v e o r r a r e f a c t i v e f i r s t a r r i v a l d e p e n d i n g on t h e t h e i r p o s i t i o n w i t h r e s p e c t t o t h e r u p t u r e p l a n e and t h e d i r e c t i o n o f m o t i o n a l o n g t h e r u p t u r e p l a n e . In t h e mine e n v i r o n m e n t however, t h e above c r i t e r i a , w i t h t h e e x c e p t i o n of p o l a r i t y , t e n d t o f a i l as f i r s t l y , t h e m i c r o e a r t h q u a k e e v e n t s a r e r a t h e r s m a l l , t h a t i s t h e r u p t u r e d i m e n s i o n s come c l o s e t o b e i n g a p o i n t s o u r c e , and s e c o n d l y t h e e x p l o s i o n s a r e n o t s i n g l e b u r s t , p o i n t s o u r c e s i n a homogeneous medium. ( i ) F r e q u e n c y C o n t e n t I t a p p e a r s t h a t t h e s o u r c e d i m e n s i o n s o f t h e 70 m i c r o e a r t h q u a k e e v e n t s a r e t o o s m a l l t o a l l o w d i s c r i m i n a t i o n b a s e d on f r e q u e n c y c o n t e n t . Hence t h i s i s n o t a u s e f u l c r i t e r i o n as b o r n e out by t h e S u l l i v a n Mine d a t a . B o t h e x p l o s i o n e v e n t s and m i c r o e a r t h q u a k e e v e n t s ( i . e . weekend e v e n t s ) showed a s i m i l a r range i n f r e q u e n c y . ( i i ) G e n e r a t i o n o f Shear Waves E x p l o s i o n s , p a r t i c u l a r l y i n t h e d e v e l o p m e n t a r e a s , a r e d e t o n a t e d i n g r o u p s w i t h an o r d e r e d d e l a y p a t t e r n . An i n i t i a l b l a s t i s d e t o n a t e d c r e a t i n g a c a v i t y ( i . e . f r e e f a c e s ) a f t e r w h i c h s e v e r a l f u r t h e r c h a r g e s a r e d e t o n a t e d a r o u n d t h e c a v i t y . B r e a k a g e o c c u r s by t e n s i o n a l f a i l u r e , as t h e c o m p r e s s i o n a l wave * c h a n g e s p h a s e upon r e f l e c t i o n o f f t h e f r e e s u r f a c e , and m a t e r i a l moves i n t o t h e c a v i t y . The d i f f e r e n t i a l s t r e s s e s c r e a t e d l e a d t o t h e g e n e r a t i o n of S-waves. In f a c t , t h i s p r i n c i p a l i s u s e d by t h e o i l i n d u s t r y t o g e n e r a t e S-waves from e x p l o s i v e s o u r c e s ; t h e t e c h n i q u e i s c a l l e d SEISLAP (Tatham e t a l , 1980). ( i i i ) Coda Shape Due t o t h e e x p l o s i o n t i m e d e l a y s , t h e coda shape c r i t e r i o n i s no l o n g e r a p p l i c a b l e . ( i v ) P o l a r i t y The d i r e c t i o n of f i r s t m o t i o n c o u l d not be d e t e r m i n e d s u f f i c i e n t l y w e l l t o e n a b l e i t s use as a d i s c r i m i n a t i o n c r i t e r i o n . The most s e r i o u s p r o b l e m i n e v e n t d i s c r i m i n a t i o n was t h e l a c k o f p o l a r i t y i n f o r m a t i o n . I t was hoped t h a t a f i r s t m o t i o n 71 a n a l y s i s o f t h e m i c r o e a r t h q u a k e s would e n a b l e t h e c o n s t r u c t i o n of f a u l t p l a n e s o l u t i o n s and h e n c e a l l o w some more c o n c l u s i v e comments t o be made on t h e s t y l e of t h e f a i l u r e i n t h e mine a r e a and on t h e n a t u r e , o r a b s e n c e , o f a s t r e s s r e g i m e . U n f o r t u n a t e l y , w i t h t h e r e s t o f t h e d a t a s e t b e i n g o f l o w e r m a g n i t u d e t h a n t h e t e s t e v e n t s , f i r s t a r r i v a l s were o f t e n n o t as d i s t i n c t . An e x a m i n a t i o n of 55 known e x p l o s i o n e v e n t s showed t h a t f o r e a c h s t a t i o n u s e d t h e r e was r o u g h l y a 50:50 d i s t r i b u t i o n of p o s i t i v e and n e g a t i v e f i r s t a r r i v a l p o l a r i t i e s ; ( t h e o n l y e x c e p t i o n b e i n g PIT, l o c a t e d above t h e s o u t h e r n edge of t h e mine, w h i c h g e n e r a l l y r e c o r d e d p o s i t i v e p o l a r i t i e s ) . The r e a s o n f o r t h e p r o b l e m i s o b v i o u s when we c o n s i d e r t h e o r i e n t a t i o n o f t h e v e r t i c a l s e i s m o m e t e r s w i t h r e s p e c t t o t h e zone i n w h i c h t h e m a j o r i t y of e v e n t s o c c u r . F i g u r e 5.7 shows t h e r a d i a l d i s t a n c e o f t h e s e i s m o m e t e r s and t h e i r e l e v a t i o n w i t h r e s p e c t t o t h e open p i t . In t h e c a s e of a u n i f o r m v e l o c i t y m odel, t h a t i s a s s u m i n g s t r a i g h t l i n e t r a v e l p a t h s , i t becomes c l e a r f r o m t h e d i a g r a m t h a t t h e component o f m o t i o n w h i c h t h e v e r t i c a l s e i s m o m e t e r s a r e a b l e t o measure i s much s m a l l e r t h a n t h e r a d i a l h o r i z o n t a l component. C o n s i d e r t h r e e c a s e s e v i d e n t i n F i g u r e 5.7; f i r s t l y t h e s t a t i o n s above t h e p l a n e o f t h e open p i t b l a s t e x p e r i e n c e a s m a l l d i r e c t upward v e r t i c a l component o f f i r s t m o t i o n . S e c o n d l y , t h e s u r f a c e s t a t i o n s below t h e p l a n e o f t h e e x p l o s i o n s h o u l d e x p e r i e n c e a s m a l l d i r e c t v e r t i c a l component o f f i r s t m o t i o n downwards. I n p r a c t i c e however ( a s i n d i c a t e d by t h e p o s i t i v e t e s t e x p l o s i o n p o l a r i t i e s ) d i f f r a c t i o n e f f e c t s due t o . s u r f a c e t o p o g r a p h y , and t h e f a c t t h a t a s l i g h t v e r t i c a l v e l o c i t y g r a d i e n t p r o b a b l y d o e s e x i s t , means t h a t t h e o o o. CO <D- o fl O +-> <ti o > o <D O o A PIT " N C N I S H F i j D39 surface station underground station P M P LOI (•J D27 SUL MRK PLAN E_ 0F_ OPEN PIT BLAST MOR 0 2000 4000 6000 distance (feet) 8000 10000 F i g u r e 5 . 7 S t a t i o n E l e v a t i o n and R a d i a l D i s t a n c e w i t h r e s p e c t t o the Open - j P i t . M Star r e p r e s e n t s e l e v a t i o n of open p i t b l a s t s and the dashed l i n e separates those s t a t i o n s l o c a t e d above the plane of the b l a s t from those l o c a t e d below. 73 r a y s a r r i v i n g a t t h e s e s t a t i o n s a r e l a r g e l y h o r i z o n t a l w i t h a s m a l l upward v e r t i c a l component. F i n a l l y , i n t h e c a s e o f t h e two u n d e r g r o u n d s t a t i o n s t h e c a v i t y c o n t a i n i n g t h e s e i s m o m e t e r i s s m a l l w i t h r e s p e c t t o t h e P-wave l e n g t h o f .260 - 530 m so when t h e p l a n e of t h e e x p l o s i o n i s above t h e s t a t i o n s ( F i g u r e 5.7), t h e whole c a v i t y would have an i n i t i a l d i s p l a c e m e n t downwards r e s u l t i n g i n n e g a t i v e f i r s t a r r i v a l p o l a r i t i e s . In a l l c a s e s t h e v e r t i c a l component of f i r s t m o t i o n i s o n l y s u f f i c i e n t l y l a r g e f o r t h e c l o s e r s u r f a c e s t a t i o n P I T t o r e c o r d u n a m b i g u o u s l y . The more d i s t a n t s t a t i o n s r e c o r d a much s m a l l e r v e r t i c a l component s u c h t h a t i t c o u l d o n l y be r e l i a b l y p i c k e d i n t h e c a s e o f t h e l a r g e r t e s t e x p l o s i o n s . Note t h a t c a u t i o n i s r e q u i r e d when u s i n g u n d e r g r o u n d s t a t i o n s f o r p o l a r i t y , a n a l y s i s i n t h e c a s e where s o u r c e d e p t h w i t h r e s p e c t t o t h e r e c o r d i n g s t a t i o n s i s unknown. A m b i g u i t y w i l l a r i s e as t h e r e c o r d e d f i r s t m o t i o n w i l l be i n f l u e n c e d by b o t h t h e l o c a t i o n of t h e s o u r c e w i t h r e s p e c t t o t h e r e c o r d i n g s t a t i o n s and t h e n a t u r e of t h e s o u r c e . Had t h e S u l l i v a n p o l a r i t y i n f o r m a t i o n been u s a b l e , f u r t h e r s e r i o u s p r o b l e m s would have a r i s e n due t o p oor f o c a l d e p t h d e t e r m i n a t i o n . In summary, a d e t a i l e d e x a m i n a t i o n o f t h e d a t a f a i l e d t o y i e l d any u s e f u l e v e n t d i s c r i m i n a t i o n c r i t e r i a , a p a r t f r o m s e p a r a t i o n on a t e m p o r a l b a s i s . F u r t h e r s e p a r a t i o n o f t h e "weekday" e v e n t s ( F i g u r e 5.1) i s beyond t h e s c o p e of t h i s p r e s e n t s t u d y . I n o r d e r t o use p o l a r i t y i n f o r m a t i o n i n f u t u r e e x p e r i m e n t s , h o r i z o n t a l s e i s m o m e t e r s o r i e n t e d t o w a r d s t h e a r e a o f e x p e c t e d a c t i v i t y s h o u l d be d e p l o y e d . 74 5.3 HYPOCENTRE LOCATION A s e i s m i c e v e n t t h a t i s r e c o r d e d by an a r r a y of 4 s t a t i o n s can be l o c a t e d b o t h s p a t i a l l y and i n t i m e as f o l l o w s : Take t h e unknown c o o r d i n a t e s o f an e v e n t h y p o c e n t r e ( x 0 , y o » Z o ) and i t s unknown o r i g i n t i m e t 0 and l e t t h e known c o o r d i n a t e s of t h e i t h r e c o r d i n g geophone be ( x ^ y ^ Z i . ) . The d i s t a n c e t o e a c h geophone d< can.be w r i t t e n i n two ways, d, = (x, - x 0 ) 2 + (y, - y 0 ) 2 + ( z , - z 0 ) 2 d, = v ( t , - t 0 ) where t , i s t h e a r r i v a l t i m e a t t h e i t h geophone o f a p a r t i c u l a r p h a s e , and v i s i t s v e l o c i t y . E q u a t i n g t h e two e q u a t i o n s above, (x, - x 0 ) 2 + ( y , - y 0 ) 2 + ( z i " z 0 ) 2 = v 2 ( t , - t 0 ) 2 and w i t h 4 s e i s m i c s t a t i o n s r e c o r d i n g t h e e v e n t , i t i s p o s s i b l e t o s o l v e u n i q u e l y f o r t h e 4 unknowns x 0 , y 0 , z 0 and t 0 . T h i s i s known as t h e " d i r e c t s o l u t i o n " . A summary o f t h e v a r i o u s t h r e e - d i m e n s i o n a l s o u r c e l o c a t i o n t e c h n i q u e s i s g i v e n by L e i g h t o n and B l a k e (1970) w h i c h i n c l u d e s t h e " s t a n d a r d d i r e c t s o l u t i o n " . A f u r t h e r p a p e r by L e i g h t o n and D u v a l l (1972) c o n t a i n s e x c e l l e n t d i s c u s s i o n on t h e m e r i t s o f u s i n g a " l e a s t s q u a r e s " a p p r o a c h o v e r t h e " s t a n d a r d d i r e c t s o l u t i o n " method i n t e r m s of l o c a t i o n a c c u r a c y when t h e r e a r e more t h a n 4 a r r i v a l t i m e s a v a i l a b l e . The most r e c e n t d e v e l o p m e n t o f a l g o r i t h m s f o r a 3 - d i m e n s i o n a l d i s t r i b u t i o n o f s t a t i o n s i n c l u d e s work by S p o t t i s w o o d e ( 1 9 8 0 ) , C e t e (1977) and t h e m i n e r a l e n g i n e e r i n g g r o u p a t P e n n s y l v a n i a S t a t e U n i v e r s i t y (Mowrey, 1977; and H a r d i n g , 1 9 70). Two l e a s t s q u a r e s t y p e p r o g r a m s were o b t a i n e d f o r t h i s 75 s t u d y from S p o t t i s w o o d e (1980) and Mowrey ( 1 9 7 7 ) . T h a t of S p o t t i s w o o d e , w h i c h i s b a s e d on S e i d e l ' s method has been i m p l e m e n t e d on t h e U.B.C. c o m p u t e r . A d i s c u s s i o n o f S e i d e l ' s method and a l i s t i n g of t h e p r o g r a m i s i n c l u d e d i n A p p e n d i x 2. The p r o g r a m a l l o w s t h e use of b o t h P and S a r r i v a l s , w e i g h t s s t a t i o n s a c c o r d i n g t o d i s t a n c e , and c a n t a k e a c c o u n t o f v e l o c i t y v a r i a t i o n s d i r e c t l y o r t h r o u g h t i m e d e l a y s . The program i t e r a t e s q u i c k l y t o a f i n a l s o l u t i o n r e m o v i n g s t a t i o n s from t h e c o m p u t a t i o n w h i c h have t i m e r e s i d u a l s l a r g e r t h a n a s p e c i f i e d v a l u e . The t i m e r e s i d u a l f o r t h e S u l l i v a n Mine p r o j e c t , above w h i c h r e j e c t i o n would o c c u r f o r a s t a t i o n i n t h e i n n e r n e t , was c h o s e n t o be a b o u t e q u a l t o t h e t o t a l a r r i v a l t i m e e r r o r of ±0.03 s. The seismograms o f t h e r e j e c t e d a r r i v a l s c o u l d t h e n be r e - a n a l y s e d f o r m i s t a k e s i n t h e f i r s t a r r i v a l p i c k s or f o r t i m i n g e r r o r s . In t h e c a s e o f t h e emergent e v e n t s t h e t i m e r e s i d u a l f o r a l l t h e s t a t i o n s was g e n e r a l l y much h i g h e r , o f t e n as much a s 0.1 s t o 0.2 s and i t was u s u a l l y i m p o s s i b l e t o o b t a i n an im p r o v e d f i r s t a r r i v a l p i c k . 7 6 5.4 NON-LOCATABLE EVENTS From, t h e i n i t i a l d a t a s e t of 366 e v e n t s , 266 e v e n t s were u s e d i n t h e h y p o c e n t r e l o c a t i o n p r o g r a m f o r r e a s o n s d i s c u s s e d i n s e c t i o n 5.1. I n i t i a l l y l o c a t i o n s c o u l d n o t be d e t e r m i n e d f o r 55 of them y e t t h e i r c h a r a c t e r i n d i c a t e d t h a t t h e y s h o u l d be w i t h i n t h e a r r a y a r e a . A f t e r r e p i c k i n g d i f f i c u l t f i r s t a r r i v a l s i n 22 c a s e s and e l i m i n a t i n g m i s i d e n t i f i e d S a r r i v a l p i c k s i n 6 c a s e s , 28 non l o c a t a b l e e v e n t s r e m a i n e d o f w h i c h 15 were emergent e v e n t s . The r e m a i n i n g 12 e v e n t s would n o t c o n v e r g e due t o an i n s u f f i c i e n t number o f s t a t i o n c o n s t r a i n t s . They were a l l r e c o r d e d by o n l y 4 d i g i t a l s t a t i o n s and of t h e s e a r r i v a l s a t D27 c o u l d not be u s e d b e c a u s e of u n r e s o l v a b l e t i m i n g p r o b l e m s . 5.5 IMPORTANCE OF CONSTRAINING CALCULATED HYPOCENTRES I t i s e x t r e m e l y i m p o r t a n t t h a t an e v e n t be c o m p l e t e l y s u r r o u n d e d by r e c o r d i n g s t a t i o n s i n o r d e r t h a t i t s h y p o c e n t r e may be d e t e r m i n e d a c c u r a t e l y . The p r o b l e m i s h i g h l i g h t e d i n F i g u r e 5.8 w h i c h shows t h e e p i c e n t r e s o f e v e n t s c a l c u l a t e d w i t h o u t t h e a r r i v a l a t MRK i n c l u d e d ; f o r c o m p a r i s o n F i g u r e 5.9 shows t h e e p i c e n t r a l l o c a t i o n s c a l c u l a t e d u s i n g t h e a r r i v a l s a t MRK. F i g u r e 5.8 shows t h e e v e n t s , r a t h e r t h a n a c l u s t e r i n t h e mine a r e a as t h e y r e a l l y a r e , b u t as a band o f a c t i v i t y e x t e n d i n g o u t o f t h e mine a r e a b o t h t o t h e e a s t a n d west. A number of e v e n t s e x t e n d some 2000' (600m) t o t h e west o f t h e i r t r u e l o c a t i o n s . W i t h o u t s t a t i o n MRK e a s t - w e s t c o n s t r a i n t i s p o o r compared o a o «, BOG + E x p l o s i o n E v e n t E p i c e n t r e £, Emergent Event E p i c e n t r e O " O t h e r " Event E p i c e n t r e CD + SUL k m 5' 5" KF ./~ —r s r s s S J s s s + .MO.R MAT -i -].sooa - i - . 1 Z U 0 D -1 -3000 1 •6303 "1 - 3 3 0 0 - 0 - 0 -1 3 0 0 0 G 0 0 0 .91100 : <aoo F i g u r e 5 .8 E p i c e n t r a l Map of a l l Events Located w i t h a r r i v a l MRK Excluded from the C a l c u l a t i o n s . -J The spread of the e p i c e n t r e s compared w i t h F i g u r e 5.9 i n d i c a t e s the e f f e c t s of poor s t a t i o n c o n s t r a i n t . o Q o o o o . • • SOG 4- E x p l o s i o n E v e n t E p i c e n t r e £, Emergent Ev e n t E p i c e n t r e © " O t h e r " E v e n t E p i c e n t r e k m MRK 5 5" S * KF + ^ S U L 4 ^ P M P S s s 5 S f—• / / /1 •^5 S NCN SF 5 LCF ^ MOR o o -1R300 MRT "i -15003 -9000 ~1 -6000 -3000 3000 6000 9000 !2000 F i g u r e 5.9 E p i c e n t r a l Map of a l l Events Located w i t h a r r i v a l MRK Included i n the C a l c u l a t i o n s . co When compared w i t h F i g u r e 5.8 the importance of MRK as an east-west c o n s t r a i n t can be seen. The s i g n i f i c a n c e of the event l o c a t i o n s w i l l be seen l a t e r . 79 t o t h a t i n t h e n o r t h - s o u t h d i r e c t i o n and i n o r d e r t o m i n i m i z e t h e s q u a r e s o f t h e d i s t a n c e r e s i d u a l s t h e p r o g r a m can move c a l c u l a t e d e p i c e n t r e s q u i t e e a s i l y a l o n g t h i s l i n e of weakest c o n s t r a i n t . T h e s e o b s e r v a t i o n s have an i m p o r t a n t b e a r i n g on t h e d i s c u s s i o n s c o n c e r n i n g f o c a l d e p t h s t o f o l l o w i n t h e n e x t s e c t i o n s and C h a p t e r 6. 5.6 HYPOCENTRAL ACCURACY BASED ON EXPLOSIONS The e x p e c t e d l o c a t i o n c a p a b i l i t y may be d e t e r m i n e d by c o m p a r i n g t h e c a l c u l a t e d h y p o c e n t r e s o f e v e n t s w i t h t h e i r known l o c a t i o n s . A s u i t e o f 12 e x p l o s i o n s i n t h e mine a r e a e n a b l e d t h i s t o be done. F i g u r e 5.10 shows t h e c a l c u l a t e d e p i c e n t r e s of a l l known e x p l o s i o n s and t h e a c t i v e m i n i n g a r e a s i n w h i c h t h e y a r e most l i k e l y t o have o c c u r r e d ( J . H a m i l t o n , p e r s o n a l c o m m u n i c a t i o n 1981). T h o s e e x p l o s i o n s of known l o c a t i o n a r e shown c i r c l e d and t h e i r a r e a l d i s t a n c e from t h e t r u e l o c a t i o n i n t h e mine w o r k i n g s a r e i n d i c a t e d . F i g u r e s 5.11 and 5.12 show t h e p r o j e c t i o n o f e x p l o s i o n h y p o c e n t r e s and mine w o r k i n g a r e a s o n t o a n o r t h - s o u t h and e a s t - w e s t p l a n e r e s p e c t i v e l y . T h o s e e x p l o s i o n s o f known l o c a t i o n a r e a g a i n c i r c l e d and t h e d i s p l a c e m e n t o f t h e i r c a l c u l a t e d f o c a l d e p t h s from t h e t r u e l o c a t i o n shown. The d i f f e r e n c e between t h e known and c a l c u l a t e d p a r a m e t e r s i s a l s o l i s t e d i n T a b l e 5.1, column 5.3 k m s - 1 . From t h e F i g u r e s and T a b l e we s e e t h a t t h e e p i c e n t r a l e r r o r v a r i e s f r o m 0 t o 600' (180 m) w i t h t h e d e p t h b e i n g much more p o o r l y d e t e r m i n e d but g e n e r a l l y d e e p e r t h a n t h e t r u e d e p t h . The e r r o r band r a n g e s from 200' (60 m) above t o 1600' (500 m) below t h e t r u e d e p t h . o o to CD LO •TO —I o o LO rvi -I o CD VO o a LO CD -I Q C70 0 0 Q LO o o LO LO P.MP D 2 7 ( / \ + X ^ + + + D 3 9 SHE / 80 \ \ ' £3 W o r k i n g A r e a 4 - E x p l o s i o n E p i c e n t r e <B E x p l o s i o n E p i c e n t r e l o c a t i o n known o 200m .1.500 • 2 5 0 0 .35.00 4 5 0 0 5 5 3 0 5 5 0 0 7 5 D 0 F i g u r e 5.10 C a l c u l a t e d E x p l o s i o n E p i c e n t r e s . C i r c l e d e p i c e n t r e s are of known l o c a t i o n , displacement from t h e i r t r u e p o s i t i o n i n the working areas i s i n d i c a t e d as a s o l i d l i n e . F i g u r e 5.11 C a l c u l a t e d E x p l o s i o n H y p o c e n t r e s p r o j e c t e d o n t o a N o r t h - S o u t h C r o s s S e c t i o n . The l o c a t i o n s o f t h o s e e v e n t s c i r c l e d a r e known fr o m 0 0 e x p l o s i o n r e c o r d s , d i s p l a c e m e n t f r o m t h e i r t r u e p o s i t i o n ~* i n t h e w o r k i n g a r e a s i s i n d i c a t e d a s a s o l i d l i n e . D Working A r e a -I- C a l c u l a t e d E x p l o s i o n H ypocentre © C a l c u l a t e d E x p l o s i o n H ypocentre l o c a t i o n known E - W Cross S e c t i o n o f Orebody a t 1 1 6 0 0 N PILLAR BLAST SURFACE RAMP D27 0 metres 200 '^000 .2500 3000 3500 •4000 / I 4500 5000 5500 6 0 0 0 6500 7D00 7500 8000 F i g u r e 5.12 C a l c u l a t e d E x p l o s i o n H y p o c e n t r e s p r o j e c t e d o n t o a E a s t - W e s t C r o s s S e c t i o n . The l o c a t i o n s of t h o s e e v e n t s c i r c l e d a r e known f r o m e x p l o s i o n r e c o r d s , d i s p l a c e m e n t f r o m t h e i r t r u e p o s i t i o n i n t h e w o r k i n g a r e a s i s i n d i c a t e d as a s o l i d l i n e . EVENT NUMBER VELOCITY kms 1 AND 5.1 5.2 5.3 5.4 5.5 LOCATION EPI Z EPI Z EPI z . EPI z EPI Z 73 (P-9-1) 230 +120 220 +140 200 +150 190 +160 170 +180 74 (P-9-1). 280 -600 250 -560. 220 -540 200 -500 180 -460 94 (//l RAMP) 310 -1650 330 -1450 350 -1230 370 -1000 380 -680 52 (P-9-1) 380 -1400 350 -1320 320 -1260 310 -1200 290 -1140 49 ( L - l l - 3 0 ) 325 -900 280 r-860 250 -850 210 -820 17 0 -800 47 (P-9-1) +180 140 +180 140 +180 130 +180 130 +180 45 (# RAMP) 40 -570 20 -570 0 -570 35 -57 0 40 -57 0 10 (3710 29) -1570 640 -1570 630 -1560 630 -1560 620 -1560 2 61 (PILLAR) 1070 520 -1400 530 -1400 610 -950 700 -480 75 (OPEN P) 610 -1630 580 -1320 560 -1060 560 -87 0 570 -750 199 (OPEN P) 0 -900 70 -600 90 -530 80 -500 110 -430 7 0 {ill RAMP) 50 -130 20 -150 0 -150 50 -150 80 -150 Table 5 .1 Difference between the calculated explosion hypocentres and t h e i r t-rue position, for v e l o c i t i e s ranging from 5 . 1 to 5 . 5 kms"1. EPI i s the epicentral displacement and Z i s the difference in depth. 84 The e x t r e m e l y l a r g e h y p o c e n t r a l e r r o r and t e n d e n c y f o r e v e n t f o c i t o c l u s t e r below t h e i r known p o s i t i o n i s r a t h e r d i s c o n c e r t i n g , but i t c a n be e x p l a i n e d i n terms of s t a t i o n g e o m e t r y . When we ask why t h e r e i s s u c h a l a r g e e r r o r i n t h e z - d i r e c t i o n a l o n e i t becomes c l e a r t h a t t h e same s i t u a t i o n i s o c c u r r i n g a s was seen i n F i g u r e 5.8 when l o c a t i o n s were c a l c u l a t e d w i t h o u t MRK. In t h i s c a s e , t h e a r r i v a l t i m e e r r o r s i n t h e r e s i d u a l e q u a t i o n a r e b e i n g m i n i m i z e d most e a s i l y by v a r i a t i o n i n t h e z - d i r e c t i o n . L o o k i n g a g a i n a t F i g u r e 5.7 showing s t a t i o n e l e v a t i o n v e r s u s r a d i a l d i s t a n c e , we see t h a t e ven t h o u g h an a t t e m p t was made t o c r e a t e a 3 - d i m e n s i o n a l a r r a y o f s t a t i o n s a t t h e S u l l i v a n M i n e , t h e r e i s s t i l l a p l a n e ( c l o s e t o h o r i z o n t a l ) i n w h i c h t h e s t a t i o n ' c o n s t r a i n t i s s t r o n g e s t . Due t o c a v i n g and hence r e s t r i c t e d a c c e s s above t h e S u l l i v a n M ine t h e s t a t i o n l o c a t i o n s t e n d t o f o r m a r i n g a r o u n d t h e a r e a o f g r e a t e s t a c t i v i t y . I f we c o n s i d e r t h e t h e o r e t i c a l c a s e i n w h i c h t h e s t a t i o n s f o r m a p e r f e c t c i r c l e , r e c o r d i n g P - a r r i v a l s f r o m an e v e n t o c c u r r i n g a t t h e c e n t r e of t h e a r r a y , t h e n t h e r e w i l l be no c o n s t r a i n t a t a l l i n t h e z - d i r e c t i o n . In t h e c a s e o f t h e S u l l i v a n a r r a y t h e u n d e r g r o u n d s t a t i o n s a r e a t t h e m i n i n g l e v e l and t h u s p l a c e some c o n s t r a i n t on t h e f o c a l d e p t h s ; t r a v e l - t i m e d i f f e r e n t i a l s between them and t h e s u r f a c e s t a t i o n s c o n s t r a i n most h y p o c e n t r e s t o l i e a t and below t h e o r e b o d y . 85 5.7 THE EFFECT OF CHANGES IN THE VELOCITY MODEL What i s t h e i m p o r t a n c e of t h e v e l o c i t y model i n h y p o c e n t r a l d e t e r m i n a t i o n and what wo u l d be t h e e f f e c t of c h a n g i n g t h e v e l o c i t y f r o m t h a t of of 5.30 kms" 1 d e r i v e d f r o m t h e c a l i b r a t i o n e x p l o s i o n s ? The e x p l o s i o n e v e n t s w i t h known o r i g i n c o - o r d i n a t e s were a g a i n u s e d and t h e v e l o c i t y i t e r a t e d f r o m one end o f a r e a s o n a b l e r a n g e t o t h e o t h e r , i . e . 5.1 t o 5.5 kms" 1. The e f f e c t s on t h e e p i c e n t r a l and d e p t h e r r o r s a r e l i s t e d i n T a b l e 5.1 and c a n be se e n on F i g u r e s 5.13, 5.14'and 5.15. The d a s h e d l i n e s i n d i c a t e s t h e change i n c a l c u l a t e d p o s i t i o n as t h e v e l o c i t y i s ch a n g e d f r o m 5.1 t o 5.5 kms" 1. As e x p e c t e d i n t h e h o r i z o n t a l p l a n e of maximum s t a t i o n c o n s t r a i n t , t h e r e i s v e r y l i t t l e e f f e c t a c r o s s t h e whole r a n g e of v e l o c i t i e s . T h e . e p i c e n t r a l l o c a t i o n s ( F i g u r e 5.13) a r e r a t h e r i n s e n s i t i v e t o v e l o c i t y w i t h t h e p o s i t i o n s c h a n g i n g by 0 t o 300 f t (90 m), but i n most c a s e s l e s s t h a n 200 f t (60 m). The f o c a l d e p t h s , on t h e o t h e r hand, v a r y up t o 1600 f t (500 m) w i t h t h e v e l o c i t y c h a n g e s . An i n c r e a s e i n v e l o c i t y i s seen t o p u l l t h e f o c a l d e p t h s c l o s e r t o t h e p l a n e of maximum s t a t i o n c o n s t r a i n t , b o t h from above and below t h e p l a n e ( F i g u r e s 5.14 & 5.15). The r e a s o n i s a p p a r e n t g e o m e t r i c a l l y , a s t h e a r r i v a l t i m e d i f f e r e n t i a l , A t , between s t a t i o n s i s f i x e d and v = Ad/At, where Ad i s t h e d i s t a n c e d i f f e r e n t i a l between t h e s o u r c e and t h e v a r i o u s s t a t i o n l o c a t i o n s . An i n c r e a s e d v e l o c i t y t h e r e f o r e r e q u i r e s a l a r g e r d i s t a n c e d i f f e r e n t i a l between s t a t i o n s ; t h i s i s f a c i l i t a t e d by m o v i n g t h e s o u r c e c l o s e r t o t h e p l a n e o f s t a t i o n e l e v a t i o n . I t i s c l e a r t h a t t h e v e l o c i t y c h o s e n does n o t p l a y a v e r y o o I D o a L O fM . o a CO 86 • PMP Q a in m _| s' / 1 • D27 N / £ J i + ' / o ' +, ± + T +. ' a \ i + •••• • ^ + * + • / V * D39 / Ln _ 1 cn . / • f / A S H F - - T -• § \ • ' , Calculated Explosion £ - | N /=K . f t 1 *" ' Epicentre \ •-: 1 g I • in o a in C D NRD i500 2500 3500 4500 5500 6500 750C Figure 5.13 Effect of Velocity Changes on Epicentral Location. The dotted l ines indicate the change in calculated epicentral position of the explosion events as the velocity is iterated from 5.1 kms"' to 5.5 kms"'. The cross is the position at 5.3 kms - ' . • -+ Working A r e a C a l c u l a t e d E x p l o s i o n H y p o c e n t r e N - S Cro s s S e c t i o n o f Orebody a t 4050 E metres 200 8000 - 1 850C - 1 9000 - I 9500 10000 10500 11000 "I 11S00 12000 F i g u r e 5.14 E f f e c t o f V e l o c i t y Changes on H y p o c e n t r a l L o c a t i o n , N o r t h - S o u t h C r o s s S e c t i o n . The d o t t e d l i n e s i n d i c a t e t h e c h a n g e i n c a l c u l a t e d h y p o c e n t r a l p o s i t i o n p r o j e c t e d o n t o a n o r t h - s o u t h p l a n e . The p o s i t i o n c h a n g e s i n t h e d i r e c t i o n o f t h e a r r o w s a s t h e v e l o c i t y i s i n c r e a s e d f r o m 5.1 t o 5.5 k m s ' . I I Working A r e a + C a l c u l a t e d E x p l o s i o n H y p o c e n t r e E - W Cross S e c t i o n o f Orebody a t 11600 N 0 200 metres _ | , , ! , , , , , , , 1 1 ^00D 2500 3000 3 5 0 0 4000 4500 5 0 0 0 . 5 5 0 0 6 0 0 0 6 5 0 0 7000 7500 BOOO F i g u r e 5.15 E f f e c t o f V e l o c i t y C h anges on H y p o c e n t r a l L o c a t i o n , E a s t - W e s t C r o s s S e c t i o n . The d o t t e d l i n e s i n d i c a t e t h e c h a n g e i n c a l c u l a t e d h y p o c e n t r a l p o s i t i o n p r o j e c t e d o n t o an e a s t - w e s t p l a n e . The p o s i t i o n c h a n g e s i n t h e d i r e c t i o n o f t h e a r r o w s a s t h e v e l o c i t y i s i n c r e a s e d f r o m 5.1 t o 5.5 kms" 1. 89 i m p o r t a n t r o l e i n e p i c e n t r a l l o c a t i o n , p r o v i d e d t h e s o u r c e i s w e l l s u r r o u n d e d by s t a t i o n s . To use an a r t i f i c i a l l y h i g h v e l o c i t y t o p u l l t h e f o c a l d e p t h s i n t o t h e p l a n e o f maximum s t a t i o n c o n s t r a i n t , r a t h e r t h a n t h e more a p p r o p r i a t e v a l u e o f 5.3 kms" 1 d e t e r m i n e d from t h e t e s t e x p l o s i o n s , m e r e l y s e r v e s t o d i s g u i s e t h e e r r o r s c a t t e r . T h i s would n o t p r o v i d e b e t t e r d e p t h r e s o l u t i o n . 90 CHAPTER 6: ANALYSIS AND INTERPRETATION 6.1 EVENT LOCATION, AN OVERALL PICTURE -F i g u r e 6.1 i s an e p i c e n t r a l map of a l l e v e n t s l o c a t e d d u r i n g t h e s i x week e x p e r i m e n t . The most n o t e w o r t h y f e a t u r e i s t h a t a l l t h e e v e n t s , w i t h t h e e x c e p t i o n of ;some e x p l o s i o n s and emergent e v e n t s , l i e w e l l w i t h i n t h e b o u n d a r i e s of t h e mine a r e a , and a s we s h a l l s e e a r e c o n c e n t r a t e d on t h e a c t i v e m i n i n g z o n e s . S m a l l c l u s t e r s o f e x p l o s i o n s t o t h e immediate s o u t h of t h e mine a r e a c o r r e s p o n d to" a c t i v i t y i n t h e open p i t and d e v e l o p m e n t o f t h e #1 s u r f a c e ramp. The f o u r e x p l o s i o n s n e a r MRK, t o t h e west of t h e mine were d e t o n a t e d i n #10 p i t . T h e r e i s a s c a t t e r of emergent e v e n t s w i t h i n and t o t h e n o r t h and west of t h e mine. F i g u r e 6.1 i l l u s t r a t e s t h a t t h e S u l l i v a n Mine i s h a v i n g an e x t r e m e l y l o c a l i z e d e f f e c t on i t ' s s u r r o u n d i n g s . T h e r e i s no a c t i v i t y on t h e K i m b e r l e y F a u l t (KF) t o t h e west o f t h e mine w o r k i n g s nor on t h e S u l l i v a n F a u l t (SF) t o t h e 1 s o u t h o f t h e mine. F i g u r e 6.2 i s a b l o c k d i a g r a m s howing t h e l o c a t i o n of a l l t h e e v e n t s i n t h e mine a r e a and t h e i r p r o j e c t i o n s o n t o a n o r t h - s o u t h and an e a s t - w e s t c r o s s s e c t i o n . One n o t i c e s two d i s t i n c t c l u s t e r s o f h y p o c e n t r e s on t h e e a s t - w e s t c r o s s s e c t i o n a t , and below, t h e l e v e l o f t h e mine w o r k i n g s . We r e c a l l t h a t an e v e n t h y p o c e n t r e may be l o c a t e d anywhere between 200 f t (60 m) above t o 1,600 f t (500 m) below i t ' s t r u e p o s i t i o n . I n view o o a t a o a CD • BOG E x p l o s i o n E v e n t E p i c e n t r e Emergent E v e n t E p i c e n t r e " O t h e r " E v e n t E p i c e n t r e KF a ° -I k m SUL MOR MRT -18300 1S0DG •72000 •9000 -6000 '•.3000 3000 EO00 9000 :2300 F i g u r e 6.1 E p i c e n t r a l Map of a l l E v e n t s L o c a t e d a t t h e S u l l i v a n M i n e , J u n e - J u l y , 1980. <£> The e v e n t s l a b e l l e d a s " o t h e r " c o n s i s t o f an unknown -* c o m b i n a t i o n o f mine e x p l o s i o n s and m i c r o e a r t h q u a k e e v e n t s . F i g u r e 6.2 T h r e e D i m e n s i o n a l R e p r e s e n t a t i o n o f a l l E v e n t H y p o c e n t r e s a t t h e S u l l i v a n M i n e . The e v e n t h y p o c e n t r e s a r e p r o j e c t e d o n t o t h e e a s t - w e s t , n o r t h - s o u t h and h o r i z o n t a l p l a n e s . to 93 o f t h e l a c k of c o n s t r a i n t on f o c a l d e p t h , t h e d a t a i s s u g g e s t i v e o f two s o u r c e r e g i o n s a t t h e w o r k i n g l e v e l ( F i g u r e s 5.11 & 5 . 1 2 ) . The f a c t t h a t Pomeroy e t a l (1976) and S m i t h e t a l (1974) o b t a i n f o c a l d e p t h s o f 0.5 - 1.2 km and 0.5 - 1.5 km i n t h e i r r e s p e c t i v e s t u d y a r e a s w i t h e q u i v a l e n t or weaker t i m e c o n s t r a i n t s t h a n i n t h i s e x p e r i m e n t s u g g e s t s t h a t t h e y may a l s o be s e e i n g t h e s p u r i o u s m a n i f e s t a t i o n of t h e i r a r r i v a l t i m e e r r o r s i n t h e v e r t i c a l d i r e c t i o n . T h e i r f o c a l d e p t h s may a l s o be a t , or i m m e d i a t e l y below t h e m i n i n g l e v e l . 6.2 THE EMERGENT EVENTS ' F i g u r e 6.3 shows t h e " l o c a t i o n s " of t h e emergent t y p e e v e n t s d i s c u s s e d i n t h e p r e v i o u s c h a p t e r , 10 of w h i c h l i e w i t h i n t h e mine a r e a and 12 o u t s i d e ; t h e i r s t a t i s t i c a l c e n t r e i s t o t h e n o r t h and e a s t of t h e mine. T h e r e i s no r e p o r t e d human a c t i v i t y i n t h i s r e g i o n (P. Ransom, p e r s o n a l c o m m u n i c a t i o n , 1982)., However t h e l o c a t i o n e r r o r of t h e s e e v e n t s ( d i s c u s s e d i n S e c t i o n 5.1) i s s u c h t h a t i t would be f o o l i s h t o a t t e m p t t o a s c r i b e them t o a p a r t i c u l a r f a u l t . One c o u l d s u g g e s t t h a t t h e emergent e v e n t s may o r i g i n a t e f r o m t h e K i m b e r l e y F a u l t b ut t h e s h o r t c o m i n g s of t h i s h y p o t h e s i s w i l l be d i s c u s s e d l a t e r . F i g u r e 6.4 i s a f r e q u e n c y h i s t o g r a m of e v e n t s p e r day f o r t h e s u b s e t o f 118 emergent e v e n t s t h a t were r e c o r d e d by 4 o r more d i g i t a l s e i s m o g r a p h s . A c l e a r w e e k l y c y c l e w i t h a l m o s t no a c t i v i t y on weekends i s e v i d e n t , i n d i c a t i n g a s t r o n g r e l a t i o n s h i p between t h e s e e v e n t s and m i n i n g a c t i v i t y . As o ^ BOG Emergent Eve n t E p i c e n t r e F a u l t F o o t w a l l T r a c e F a u l t S u r f a c e T r a c e MRK 5 i " J " S s s f r> S S . s ....•^PMP.. s i " D 2 7 i 11 D3-9" ' S SUL I LOJ f J r j j 5 N.RD 0 k m NCN M D R M.RT —i 3 0 0 0 I <3OD0 -jflaoo - J 5 0 0 0 —I 1 -12003 - 9 0 0 0 —I - 6 0 0 0 "1 - 3 0 0 3 GOOO ' . £ 3 0 0 F i g u r e 6.3 E p i c e n t r e s of L o c a t a b l e Emergent E v e n t s a t t h e S u l l i v a n M i n e . T h e i r s c a t t e r i s t h e r e s u l t o f d i f f i c u l t t o p i c k f i r s t a r r i v a l s . l — i — i — i — i — i — I — i — i — I — I — i — i — I — i — i — i — r M T W Th F S S M T W Th F S S M T WTh F W Th' F ' S ' S M T W Th F S S 169 175 182 189 Time ( d a y s 1980 ) F i g u r e 6.4 H i s t o g r a m , Number of E a c h day r u n s from 10:30 or p e r i o d s when t h e r e i s Emergent E v e n t s p e r Day. pm t o 10:30 pm a n d t h e weekends, no mine a c t i v i t y , a r e s h a d e d . 96 d i s c u s s e d i n C h a p t e r 5, t h e i r emergent o n s e t s and l o w e r f r e q u e n c y c o n t e n t i n d i c a t e t h a t t h e y a r e n o t t h e r e s u l t of an e x p l o s i o n o r sudden r u p t u r e , as i s t h e c a s e f o r a t y p i c a l f r o n t - e n d l o a d e d e v e n t . I t t h u s seems c l e a r t h a t t h e y a r e some form of m i c r o e a r t h q u a k e e v e n t r e l a t e d t o m i n i n g - i n d u c e d e a r t h movement. As t h e emergent e v e n t s form a s i g n i f i c a n t p r o p o r t i o n of t h e d a t a s e t ( F i g u r e 5.1), i t i s u n f o r t u n a t e t h a t n o t h i n g more d e f i n i t e c a n be s a i d . F r a n t t i (1977) o b s e r v e d s i m i l a r e v e n t s a t t h e W h i t e P i n e C opper Mine, M i c h i g a n but was a l s o u n a b l e t o a s c e r t a i n t h e i r n a t u r e . 6.3 EVENTS WITHIN THE MINE AREA, A DETAILED PICTURE Now l e t .us a n a l y s e i n more d e t a i l t h e e v e n t s o c c u r r i n g w i t h i n t h e mine a r e a . F i g u r e s 6.5 and 6.6 a r e e n l a r g e m e n t s of t h e mine c r o s s s e c t i o n s i n F i g u r e 6.2 a f f o r d i n g a more d e t a i l e d view of t h e r e l a t i o n s h i p between t h e c a l c u l a t e d f o c a l d e p t h s and t h e p r o d u c t i o n o r d e v e l o p m e n t a r e a s . On t h e e a s t - w e s t s e c t i o n ( F i g u r e 6.6) t h e two c l u s t e r s o f e v e n t s a r e a g a i n c l e a r l y s e e n A d i p p i n g i n a w e s t e r l y d i r e c t i o n and s e p a r a t e d by an a r e a i n w h i c h t h e r e i s v e r y l i t t l e a c t i v i t y . The c l u s t e r b e l o w 1 D39 a p p e a r s t o be due t o a c t i v i t y a s s o c i a t e d w i t h m i n i n g i n t h e upper l e v e l s , i n p a r t i c u l a r t h e L-11-30 and P-9-1 (4290 P SCRAM) w o r k i n g a r e a s . The l o w e r c l u s t e r , c l o s e r t o and e a s t o f D27, a p p e a r s due t o a c t i v i t y i n t h e d e e p e r w o r k i n g s s u c h a s 3905 A 1 N o t e t h a t t h e f o c i a r e not a c t u a l l y below D39, o n l y a p p a r e n t l y so b e c a u s e o f t h e p r o j e c t i o n . o CD CD ___/lT^ * CD ° ° ~"<D '— -^ o _ 4 039 o CD O ^ % t ° CD CD nffl CD Cf m CD £ ° CD % CD ° 0 Cfc) CD CD % CDn O r ~ CD CD O ° CD^  CD O t O 0 O CD 0 0 <S> ° CD CD C § 0 0 CD © Event Hypocentre CD l~l Working Area CD N - S Cross Section of Orebody at 4050 E N - S Cross Section of Orebody at 4 800 E CD O CD CD CD CD CD O CD CD I 1 1 1 1 1 1 ° 1 1 1 R00O 8500 9000 9500 10000 10500 1]000 11500 12000 12500 F i g u r e 6.5 E v e n t H y p o c e n t r e s p r o j e c t e d o n t o a N o r t h - S o u t h C r o s s S e c t i o n . s i C5ID [ p - 9 - 1 ~ ; JD39 -fS~ ^  \(L2905 A CD CD 0 CD ( D o O CD Cg,CD ' c D CD CD 0 CD O r Q " = v 3 7 1 C - 2 9 CD \ \ O CD CD CD CD 0 CD CD CD CD © CD CD CD CD CD CD CD CD CD CD CD CD CD CD CD D27 CD © Event Hypocentre • Working Area E - W Cross Section of Orebody at 11600 N —I "/OOO - 1 /500 0^00 - 1 1 2500 3000 3500 4000 4500 5000 5500 GOOOi 6500 8000 VD F i g u r e 6.6 E v e n t H y p o c e n t r e s p r o j e c t e d onto' an E a s t - W e s t C r o s s °° S e c t i o n . 99 RAMP and 3710-29 SCRAM. The b a n d - l i k e n a t u r e of t h e c l u s t e r s i s due t o t h e l a c k of c o n s t r a i n t i n t h e v e r t i c a l d i r e c t i o n a s d e s c r i b e d e a r l i e r . The s o u t h - w e s t e r l y d i p v i s i b l e i n t h e e a s t - w e s t s e c t i o n ( F i g u r e 6.6 and a l s o i n F i g u r e s 5.11 and 5.12) seems t o be a t t r i b u t a b l e t o t h e s t a t i o n g e o m e t r y . The p l a n e of maximum c o n s t r a i n t i s a c t u a l l y one d i p p i n g t o t h e n o r t h - e a s t so t h e d i r e c t i o n o f weakest c o n s t r a i n t , a t r i g h t a n g l e s , i s t h a t i n d i c a t e d by t h e band of e v e n t s . I t i s i m p o r t a n t t o n o t e t h a t p r o j e c t i o n o f t h e h y p o c e n t r e s o n t o t h e h o r i z o n t a l p l a n e w i l l l e a d t o an a p p a r e n t s o u t h - w e s t e r l y d i s p l a c e m e n t o f t h e e p i c e n t r e s as has been o b s e r v e d i n some c a s e s ( F i g u r e 5.10). F i g u r e 6.7 i s an e n l a r g e m e n t of t h e mine a r e a and e p i c e n t r e l o c a t i o n s seen e a r l i e r i n F i g u r e 6.1. No d i s t i n c t l i n e a t i o n s o f t h e e v e n t e p i c e n t r e s a r e a p p a r e n t , and r e c a l l i n g t h a t an e p i c e n t r a l e r r o r of up t o 600 f t (180 m) may e x i s t , i t would t h u s be u n w i se t o a t t e m p t t o d e f i n e any p r e v i o u s l y unmapped f a u l t s on t h i s b a s i s . F i g u r e 6.8 i s a map showing t h e f o o t w a l l t r a c e of known f a u l t s w i t h i n t h e S u l l i v a n Mine . T h i s f i g u r e may be d i r e c t l y o v e r l a i n upon F i g u r e 6.7 so t h a t a d i r e c t c o m p a r i s o n c a n be made between t h e e v e n t e p i c e n t r e s and t h e f a u l t t r a c e s . I t i s p o s s i b l e t h a t s t r e s s r e l e a s e w i t h i n t h e mine a r e a may be o c c u r r i n g a l o n g p o r t i o n s of t h e S u l l i v a n ( S F ) , Number-two (N 2 ) , B u r c h e t t ( B F ) , A l p h a - B e t a p a i r ( A B ) , J o n e l ( J F ) and Hamlet (HF) f a u l t s . An i n t e r e s t i n g f e a t u r e i s t h e a b r u p t t e r m i n a t i o n o f a c t i v i t y t o t h e west of t h e S u l l i v a n f a u l t f o o t w a l l t r a c e . T h i s i s a l s o c l e a r i n t h e e a s t - w e s t mine c r o s s s e c t i o n ( F i g u r e 6.6). ~3B I. ca Event Ep i c e n t r e — F o o t w a l l Trace Surface Trace QWorking Area T T "1 0500 3*» 4SS6 5S0O F i g u r e 6.7 Event Epice n t r e s i n the Mine Area. F i g u r e 6.8 F a u l t s i n the Mine Area. F i g u r e 6.9 A c t i v e Blocks, June-July, 1980. The s o l i d l i n e i s a 600 f t d i s t a n c e contour around the working area. 7500 103 I t i s a p p a r e n t t h a t t h e r e was no a c t i v i t y on any f a u l t o u t s i d e t h e mine b o u n d a r i e s and t h a t i f any a c t i v i t y was o c c u r r i n g on f a u l t s w i t h i n t h e mine a r e a , i t was c o n f i n e d t o t h o s e p o r t i o n s v e r y n e a r t o t h e w o r k i n g a r e a s . F i g u r e 6.9 i s a map showing t h e b l o c k s i n w h i c h a c t i v e o r e r e m o v a l , o r mine d e v e l o p m e n t , was t a k i n g p l a c e d u r i n g t h e p e r i o d J u n e - J u l y , 1980. A l i n e o f r a d i u s 600 f t (180 m), c o r r e s p o n d i n g t o t h e maximum e p i c e n t r a l l o c a t i o n e r r o r d e t e r m i n e d i n C h a p t e r 5, has been drawn a r o u n d t h e a c t i v e a r e a s . On t h i s b a s i s , any e v e n t o c c u r r i n g w i t h i n t h e e r r o r b o u n d a r y c a n be a s c r i b e d t o m i n i n g a c t i v i t y o r a s s o c i a t e d s t r e s s r e l e a s e t o t a l l y w i t h i n t h e a c t i v e b l o c k s . F i g u r e 6.9 o v e r l a y s d i r e c t l y o n t o F i g u r e s 6.8 and 6.7 and i t i s c l e a r t h a t a l m o s t e v e r y e v e n t i s l o c a t e d w i t h i n t h i s  r e g i o n . O n l y s e v e n e v e n t s , e x c l u d i n g t h e emergent t y p e s , l o c a t e o u t s i d e , but v e r y c l o s e t o , t h e 600 f t e r r o r b o u n d a r y . F i g u r e 6.10 shows t h e l o c a t i o n of c a v e a r e a s i n t h e S u l l i v a n M i n e , t h a t i s a r e a s i n w h i c h t h e r e m o v a l o f o r e has l e d t o h a n g i n g w a l l s l u m p i n g . The t e e t h on t h e l i n e s p o i n t i n w a r d t o t h e downdropped p o r t i o n . F i g u r e 6.11, e v e n t e p i c e n t r e s i n t h e mine a r e a , when o v e r l a i n upon F i g u r e 6.10 shows t h a t t h e r e i s an a p p a r e n t c o r r e l a t i o n between e v e n t l o c a t i o n and t h e edges of t h e c a v e a r e a s , p a r t i c u l a r l y i n t h e l a r g e n o r t h w e s t e r n most c a v e . A c o n c e n t r a t i o n of e p i c e n t r e s l i e n e a r t h e e a s t e r n and s o u t h e r n edges of t h i s c a v e a r e a and a l s o t h e w e s t e r n edge w h i c h i s c o i n c i d e n t w i t h t h e S u l l i v a n f a u l t . F o u r o f t h e s e e v e n t s a r e t h o s e whose e p i c e n t r e s l o c a t e o u t s i d e t h e 600 f t e r r o r b o u n d a r y a b o u t t h e a c t i v e a r e a s , d e s c r i b e d a b o v e . The n o r t h e a s t e r n edge of t h i s c a v e a r e a w h i c h i s c o i n c i d e n t w i t h t h e Number-two f a u l t , 104 F i g u r e 6.10 Cave A r e a s above t h e S u l l i v a n M i n e . Figure 6.11 Event Epicentres i n the Mine Area. 106 a l s o shows some a c t i v i t y . The e a s t e r n m o s t c a v e a r e a i s bounded by a p o r t i o n of t h e B u r c h e t t f a u l t and t h e A l p h a - B e t a f a u l t p a i r e a r l i e r d e s c r i b e d as showing a c t i v i t y a s s o c i a t e d w i t h p o s s i b l e r e a c t i v a t i o n . The e v e n t s n e a r t h e n o r t h e r n Hamlet f a u l t seem t o o c c u r where t h e f a u l t i n t e r s e c t s a p o r t i o n o f t h e s o u t h e r n c a v e a r e a . F i g u r e 6.12 shows e p i c e n t r a l l o c a t i o n s of t h e s u b s e t o f e v e n t s o c c u r r i n g on t h e weekends, t h a t i s f r o m 10 pm on F r i d a y s ( f o l l o w i n g t h e l a s t a f t e r n o o n s h i f t ) t o 1 0 p m on Sundays ( t h e b e g i n n i n g o f t h e Monday m o r n i n g g r a v e y a r d s h i f t ) . We can be r e a s o n a b l y s u r e t h a t t h e weekend e v e n t s c o n t a i n no e x p l o s i o n s and t h a t t h e y p r o b a b l y r e p r e s e n t t h e random r e l e a s e o f s t r e s s t h a t has b u i l t up i n v a r i o u s a r e a s of t h e mine due t o a c t i v i t y d u r i n g t h e week. About 60% of t h e e v e n t s o c c u r r i n g a t t h i s t i m e l o c a t e w i t h i n ±200 f t of t h e e dges of t h e c a v e a r e a s . 6.4 EVENT ORIGIN TIME ANALYSIS A d e t a i l e d knowledge of e x a c t l y when e a c h e v e n t o c c u r s i s i m p o r t a n t , p a r t i c u l a r l y i n d e t e r m i n i n g t h e o v e r a l l r e l a t i o n s h i p between m i c r o s e i s m i c a c t i v i t y and m i n i n g c y c l e s . I t a l l o w s us t o examine f a c t o r s s u c h as r a t e s of m i c r o e a r t h q u a k e a c t i v i t y f o l l o w i n g l a r g e e x p l o s i o n s and t h e s t r e s s r e l a x a t i o n t i m e . A n a l y s i s was done u s i n g t h e 1651 e v e n t s r e c o r d e d by 2 o r more s t a t i o n s and an e x t r e m e l y c l o s e c o r r e l a t i o n w i t h m i n i n g a c t i v i t y was f o u n d . F i g u r e 6.13 i s a f r e q u e n c y h i s t o g r a m o f t h e number o f e v e n t s r e c o r d e d p e r day o v e r t h e p e r i o d o f t h e e x p e r i m e n t where o t o 1 07 I o o i n m . o a i n o a i n Q O i n o _ l PMP SULLIVAN FAULT NUMBER TWO FAULT D27 JONEL FAULT <3 CD BURCHETT FAULT ALPHA & BETA FAULTS o o i n . t n is-1 CO o o i n . c o • D39 ° 4 SHF • PIT 1500 2500 3500 4500 Weekend Event O 10pm Friday - 10pm Sunday July 11, 1980 P i l l a r Blast <i] 8 minutes <U 12 minutes <H 21 minutes <^ ] 125 minutes <U 160 minutes 5500 6500 7500 F i g u r e 6.12 E p i c e n t r a l - L o c a t i o n s o f t h e Weekend E v e n t s . The numbered t r i a n g l e s i n d i c a t e t h e c a l c u l a t e d p o s i t i o n and t i m i n g of t h e l a r g e r e v e n t s t r i g g e r e d by t h e p i l l a r b l a s t . The t r u e l o c a t i o n o f t h e p i l l a r b l a s t i s shown a s a s t a r . 108 e a c h day r u n s from 10:30 pm t o 10:30 pm and i n c l u d e s t h e t h r e e 8 hour s h i f t s , g r a v e y a r d , m o r n i n g and a f t e r n o o n . The most s t r i k i n g f e a t u r e i s t h e w e e k l y c y c l e w i t h d i s t i n c t lows c o r r e s p o n d i n g t o t h e weekends. The number of e v e n t s t h a t o c c u r on a S a t u r d a y i s g r e a t e r t h a n on a Sunday i n a l l c a s e s as s t r e s s r e l a x a t i o n e v e n t s from t h e i m m e d i a t e l y p r e c e d i n g a f t e r n o o n s h i f t a r e t a i l i n g o f f i n t o t h e S a t u r d a y p e r i o d . T h i s i s e s p e c i a l l y a p p a r e n t on t h e f i n a l S a t u r d a y o f t h e e x p e r i m e n t w h i c h has an e x t r e m e l y h i g h a v e r a g e r a t e of a c t i v i t y a s t h e F r i d a y a f t e r n o o n s h i f t ended t h a t week w i t h t h e enormous J u l y 11, 1980 p i l l a r b l a s t . . F i g u r e 6.14 shows a p o r t i o n of t h e h i s t o g r a m ( F i g u r e 6.13) w i t h an expanded t i m e s c a l e where e a c h day now c o n s i s t s o f t h r e e c o l u m n s , e a c h c o r r e s p o n d i n g t o an 8 h o u r s h i f t p e r i o d . The c h a n g i n g amounts of a c t i v i t y i n e a c h s h i f t i s c l e a r l y r e f l e c t e d i n t h e r e c o r d e d m i c r o s e i s m i c a c t i v i t y . In g e n e r a l t h e g r a v e y a r d s h i f t shows t h e l o w e s t l e v e l of a c t i v i t y , 2.0 e v e n t s / h o u r , w i t h t h e a v e r a g e r a t e i n c r e a s i n g i n t h e d a y s h i f t t o 3.0 e v e n t s / h o u r . The a f t e r n o o n s h i f t t e n d s t o have t h e h i g h e s t a v e r a g e r a t e of a c t i v i t y , 3.5 e v e n t s / h o u r . A t t h e end of t h e day t h e r e i s a l w a y s a marked d r o p i n t h e a v e r a g e a c t i v i t y w i t h t h e commencement o f t h e g r a v e y a r d s h i f t . The weekends have an a v e r a g e r a t e o f 1 e v e n t / h o u r . A d e t a i l e d e x a m i n a t i o n o f t h e d a t a showed t h a t i n 70% o f a l l t h e s h i f t p e r i o d s examined t h e r e was a d r o p i n t h e number of e v e n t s o b s e r v e d i n t h e f i r s t h o u r o f t h e new s h i f t . T h i s i s c o n s i s t e n t w i t h t h e f a c t t h a t d u r i n g t h i s f i r s t h o u r t h e m i n e r s a r e s t i l l t r a v e l l i n g t o and p r e p a r i n g t h e i r w o r k i n g a r e a s . I n 109 110 —I 100 -\ 90H 80-\ '61 169 175 182 189 196 T i me ( Days 1980 ) F i g u r e 6.13 H i s t o g r a m , Number of Events per Day. Days run from 10:30 pm to 10:30 pm and the weekends are shaded to i n d i c a t e that work i s not t ak ing p lace in the mine at t h i s t ime. F i g u r e 6.14 H i s t o g r a m , Number of E v e n t s p e r 8 Hour S h i f t P e r i o d . E a c h day i s b r o k e n up i n t o t h e t h r e e 8 hour s h i f t s , g r a v e y a r d , m o r n i n g and a f t e r n o o n . The weekends a r e s h a d e d t o i n d i c a t e t h a t no work i s t a k i n g p l a c e i n t h e mine a t t h i s t i m e . 111 g e n e r a l t h e r e was no p a t t e r n w i t h i n e a c h s h i f t due t o t h e f a c t t h a t m i n i n g and s m a l l b l a s t i n g t a k e s p l a c e t h r o u g h o u t t h i s p e r i o d . F i g u r e 6.15 a l l o w s us t o s t u d y i n d e t a i l t h e way i n w h i c h m i n i n g i n d u c e d s t r e s s i s r e l e a s e d ; i t i s a g r a p h showing t h e number of e v e n t s o c c u r r i n g p e r h o u r . The s p i k i n e s s o f t h e g r a p h , ( i . e . from 0 up t o 29 -events may o c c u r i n t h e s p a c e o f an h o u r ) , i n d i c a t e s t h e q u a n t i z e d n a t u r e o f t h e s t r e s s r e l e a s e . The c o r r e l a t i o n o f many of t h e s p i k e s w i t h s h i f t b r e a k t i m e s and Cominco r e c o r d s , as w e l l a s t h e i r n o t a b l e a b s e n c e on weekends, s u g g e s t s t h a t ' t h e y r e p r e s e n t e x t r e m e l y h i g h r a t e s o f m i c r o e a r t h q u a k e a c t i v i t y i m m e d i a t e l y f o l l o w i n g l a r g e mine e x p l o s i o n s . The " s i z e " of t h e e v e n t s making up t h e s p i k e s i s shown as a p i e d i a g r a m above e a c h s p i k e and as one can s e e , t h e m a j o r i t y of t h e s e e v e n t s were r e c o r d e d by o n l y 2 o r 3 d i g i t a l s e i s m o g r a p h s w h i c h means t h a t t h e y were g e n e r a l l y s m a l l and not s u i t a b l e f o r l o c a t i o n on our a r r a y . E x a m i n a t i o n o f some of t h e l a r g e r s p i k e s shows t h a t a b o u t h a l f t h e e v e n t s making up t h e s p i k e f o r t h a t hour o c c u r i n t h e f i r s t 10 m i n u t e s f o l l o w i n g a major mine e x p l o s i o n . F i g u r e 6.16 shows t h e number o f e v e n t s o c c u r r i n g p e r 10 m i n u t e p e r i o d f o l l o w i n g an a f t e r n o o n s h i f t b r e a k b l a s t a t 10:05, J u l y 9, 1980. I t i s c l e a r f r o m t h e f i g u r e t h a t some 20 m i c r o e a r t h q u a k e s were i n d u c e d i n t h e f i r s t 10 m i n u t e s . A n o t h e r good example i s s e e n i n F i g u r e 6.17, a h i s t o g r a m w h i c h shows t h e number o f e v e n t s o c c u r r i n g p e r h o u r a t t h e t i m e o f t h e J u l y 11, 1980 p i l l a r b l a s t . The b l a s t t o o k p l a c e i m m e d i a t e l y p r i o r t o t h e s t a r t o f a weekend so t h a t i t was p o s s i b l e t o o b s e r v e an e x p l o s i o n f r e e d e c a y p e r i o d . The < 4 S T A T I O N S TIME (DRTS) F i g u r e 6.15 Histogram, Number of Events per Hour. P i e diagrams above s p i k e s i n d i c a t e the s i z e of the s t r e s s r e l e a s e events f o l l o w i n g a mine e x p l o s i o n . The number above each diagram i n d i c a t e s the percentage of events recorded by four or more s t a t i o n s . c i o 2 2 -20 -1 8 -16 -14 -1 2 -10-« 8-| C > 4 H 2 ^ —I—I 3:05 3:35 S i z e of Re l axa t ion E vents July 9 , 1980 A f t e r n o o n Sh i f t B reak Blast — i — i — I — i — r 4:05 4:35 5:05 T ime U .T F i g u r e 6.16 Histogram, Number of Events per 10 minute P e r i o d d u r i n g the J u l y 9, 1980 Aft e r n o o n S h i f t Break B l a s t . The p i e diagram above the s p i k e i n d i c a t e s t h a t o n l y 5% of the events i n t h i s 10 minute p e r i o d were l a r g e enough to be recorded by 4 or more d i g i t a l s t a t i o n s . 10-, 3 o I C CD > LU 20-18-16-14-12-10-8-6-4 -2-1-z July 1980 Pi l lar B last Day 194 4 :40 U.T. > 2 A F T E R N O O N S H I F T 1 , ~[ r - i — r 4 4 0 5:40 UNIVERSAL TIME ( H O U R S ) 6:40 4 W E E K E N D 1 1—'• I T 5:40 T 1 1 1 1 1 1 r 10:40 15:40 16 % S i z e of Events Recorded 4:40 - 7:40 0:40 —I T 20:40 Universal Time hours F i g u r e 6.17 H i s t o g r a m , Number of E v e n t s p e r Hour f o l l o w i n q t h e J u l y 11, 1980 t h r e e s t a g e P i l l a r B l a s t . An e x p a n d e d t i m e s c a l e a l s o shows t h e number o f e v e n t s o c c u r r i n g p e r 10 m i n u t e p e r i o d f o l l o w i n g t h e b l a s t . 1 15 m a j o r i t y o f t h e s t r e s s r e l e a s e o c c u r r e d i n t h e f i r s t hour f o l l o w i n g t h e b l a s t a n d , i n f a c t , t h e f i r s t 10 m i n u t e s a s s e e n on t h e expanded tim e s c a l e . I t t o o k however a p p r o x i m a t e l y 8 h o u r s f o r t h e g r o u n d t o c o m p l e t e l y r e l a x , t h a t i s f o r t h e number of e v e n t s p e r hour t o d r o p t o t h e n o r m a l weekend l e v e l o f a b o u t 1 e v e n t / h o u r . O n l y 5 e v e n t s o c c u r r e d i n t h i s p e r i o d t h a t were l a r g e enough t o be l o c a t e d and t h e i r a r e a l d i s t r i b u t i o n ( F i g u r e 6.12) i n d i c a t e s t h a t a t l e a s t 4 d i d not o c c u r w i t h i n t h e e x p l o s i o n c a v i t y . The t h r e e - s t a g e p i l l a r b l a s t was t h e l a r g e s t e v e n t r e c o r d e d d u r i n g t h e e x p e r i m e n t . A more t y p i c a l r e l a x a t i o n t i m e f o r t h e n o r m a l week e n d i n g s c a n be seen i n F i g u r e 6.18; t h e l e v e l of a c t i v i t y r e t u r n s t o b a c k g r o u n d a f t e r t h e f i r s t h o u r . 1 16 8 -\ 6 A 2 A JUNE 20 i — i — i — i — i — I — r 0:30 5:30 DAY 173 U.T. 10:30 - 1 IE 27 J — 1 0 30 i i DAY 1 5: BO i I 30 U.T. i i 10:30 ,—1 ! JULY 4 1 0:30 1 5: 30 I I 1 1 1 1 10:30 DAY 187 U T. J F i g u r e 6.18 Histogram, Number of Events per Hour f o r the S t a r t of the Weekends commencing 10:30 pm on June 20, June 27 and J u l y 4, 1980. Shaded p o r t i o n s r e p r e s e n t weekend hours. 117 CHAPTER 7j_ CONCLUSIONS, SPECULATIONS AND SUMMARY The f i n d i n g s of t h e 1980 S u l l i v a n Mine e x p e r i m e n t may be summarized as f o l l o w s : ( i ) The i n f l u e n c e of m i n i n g a c t i v i t y a t t h e S u l l i v a n Mine i s e x t r e m e l y l o c a l i z e d . T h e r e i s no e v i d e n c e t o s u g g e s t t h a t t h e m i c r o e a r t h q u a k e s a r e o c c u r r i n g a t any s i g n i f i c a n t d i s t a n c e f r o m t h e mine f a c e s or c a v e a r e a s ; 97% o f t h e e v e n t s o c c u r w i t h i n t h e 600 f t (180 m) e r r o r c o n t o u r a b o u t t h e a c t i v e w o r k i n g a r e a s and a l l e v e n t s o c c u r w i t h i n 600 f t o f b o t h t h e w o r k i n g a r e a s and c a v e z o n e s . ( i i ) The o n l y t y p e s of s t r e s s r e l e a s e e v e n t s t h a t we c a n say w i t h c e r t a i n t y a r e o c c u r r i n g a t t h e S u l l i v a n Mine a r e : (a) S t r e s s r e l e a s e i n immediate r e s p o n s e t o t h e e x p l o s i o n a c t i v i t y , as i n d i c a t e d by t h e l a r g e number of s m a l l e v e n t s f o l l o w i n g l a r g e mine b l a s t s ( F i g u r e s - 6.16, 6.17 & 6.18). The e v e n t s a r e p r o b a b l y due t o r e l a x a t i o n o f t h e r o c k i n t h e s e v e r e l y s t r a i n e d w a l l s of t h e newly f o r m e d c a v i t i e s a n d p r o b a b l y a l s o i n c l u d e t h o s e r e s u l t i n g from s h e a r f a i l u r e c a u s e d by d i f f e r e n t i a l l o a d i n g and u n l o a d i n g a t t h e c a v i t y e d g e s . (b) S t r e s s r e l e a s e i n t h e zone o f i n d u c e d t e n s i l e s t r e s s above t h e m i n i n g c r e a t e d c a v i t i e s . Such s t r e s s r e l e a s e i s s u p p o r t e d by t h e p h y s i c a l p r e s e n c e o f c a v e z o n e s above t h e mine, " r e p o r t s o f a i r b l a s t s f o l l o w i n g m a j o r mine e x p l o s i o n s and t h e p o s s i b l e a s s o c i a t i o n of c a l c u l a t e d e p i c e n t r a l l o c a t i o n s w i t h t h e e dges o f t h e c a v e z o n e s . The l a r g e e p i c e n t r a l l o c a t i o n e r r o r and t h e i n a b i l i t y t o c a l c u l a t e f a u l t p l a n e s o l u t i o n s w e igh s t r o n g l y a g a i n s t making 118 any more d e f i n i t i v e s t a t m e n t s ; i t i s i m p o s s i b l e t o d e t e r m i n e what p r o p o r t i o n o f t h e "weekday" e v e n t s a r e m i c r o e a r t h q u a k e s and a l s o t h e e x a c t n a t u r e of t h e i r s o u r c e mechanisms ( i i i ) F i g u r e 7.1 i s a summary o f t h e f i g u r e s i n C h a p t e r 6 h i g h l i g h t i n g t h e r e l a t i o n s h i p between c a v e z o n e s , f a u l t s and c a l c u l a t e d e v e n t e p i c e n t r e s . T h e r e a p p e a r s t o be a more d e f i n i t e a s s o c i a t i o n between t h e e p i c e n t r a l l o c a t i o n s and t h e e dges o f c a v e a r e a s and i t i s i n t e r e s t i n g t o o b s e r v e t h a t when a c t i v i t y d o e s seem t o o c c u r a l o n g f a u l t s , t h e y a r e p r o x i m a l t o c a v e e d g e s . In f a c t i t a p p e a r s t h a t t h e t h e f a u l t s may be c o n t r o l l i n g t h e c a v e b o u n d a r y shape i n t h e s e a r e a s . The s u g g e s t i o n i s t h a t some o f t h e l a r g e r mine e x p l o s i o n s may t r i g g e r t h e r e l e a s e of u n s t a b l e h a n g i n g w a l l b l o c k s i n t h e v i c i n i t y o f c a v e a r e a s . C o n s i d e r as an example t h e 5 l o c a t a b l e e v e n t s f o l l o w i n g t h e J u l y 11, 1980 p i l l a r b l a s t ( F i g u r e 6.12). A l l b u t one a r e more t h a n 600 f t from t h e p i l l a r l o c a t i o n i m p l y i n g t h a t t h e y do not o r i g i n a t e f r o m w i t h i n t h e e x p l o s i o n c a v i t y ; and a l l e x e p t one l o c a t e w i t h i n 300 f t o f t h e c a v e zone e d g e s . The t r i g g e r i n g i s n o t immediate w i t h t h e e v e n t s o c c u r r i n g 8 min, 12 min, 21 min, 125 min and 160 min a f t e r t h e p i l l a r b l a s t . F i g u r e 5.6 i s a s e i s m o g r a m of t h e 21 m i n u t e e v e n t . The s u g g e s t i o n t h a t t h e s e e v e n t s r e p r e s e n t h a n g i n g w a l l c o l l a p s e i s i n a c c o r d a n c e w i t h r e p o r t e d a c t i v i t y d u r i n g t h e h o u r s f o l l o w i n g t h e p i l l a r b l a s t ; t h e r e were s e v e r a l "bumps" w i t h a s s o c i a t e d a i r b l a s t s w h i c h were i n t e r p r e t e d as " s l o u g h s of g r o u n d " ; t h a t i s c o l l a p s e o f t h e mine r o o f (H. P e a r s o n , p e r s o n a l c o m m u n i c a t i o n , 1980). o o in 119 J o a LO m o a LO CM. a tn PMP SULLIVAN-FAULT o o in o _| o o CD O o £ -I 00 NUMBER TWO FAULT D27 JONEL FAULT r - - a ^ r o © 0 CD Vo CS+ J * \ ALPHA & BETA 0 % .0 HAMLET FAULT <» j \ AL: +30 \D A + a o 7 BURCHETT D39 a SHF 4 + FAULTS SURFACE RAMP DEVELOPMENT BLASTING o o LO . • P+IT NRD o a LO . 10 1500 2500 3500 4500 5500 6500 7500 F i g u r e 7.1 R e l a t i o n s h i p between E v e n t E p i c e n t r e s , Cave A r e a s and F a u l t s . F o r c l a r i t y o n l y t h o s e p o r t i o n s o f c a v e z o n e s and f a u l t s a p p a r e n t l y a c t i v a t e d by m i n i n g have been i n c l u d e d . 120 ( i v ) T h e r e i s no e v i d e n c e t o s u g g e s t t h e p r e s e n c e of any " l o c k e d " i n " o r s t o r e d s t r e s s e s s i m i l a r t o t h o s e o b s e r v e d by McGarr e t a l (1975) a t t h e E a s t Rand P r o p r i e t a r y M i n e , nor t h e p r e s e n c e o f any r e g i o n a l l y c o m p r e s s i v e t e c t o n i c s t r e s s e s s u c h a s r e q u i r e d by S m i t h e t a l (1974) and Pomeroy e t a l ( 1 9 7 6 ) . I n t h e above c a s e s some o f t h e e a r t h q u a k e e v e n t s i n v o l v e d more e n e r g y r e l e a s e t h a n t h a t p r o v i d e d by t h e man-made a c t i v i t y t h a t t r i g g e r e d them. T h i s i s r e f l e c t e d a l s o i n t h e h i g h e r b - v a l u e s ( o r more s m a l l e v e n t s compared t o b i g ones, as w o u l d be e x p e c t e d i n a c o l l a p s e e n v i r o n m e n t ) c a l c u l a t e d by E l l i s (1977) f o r t h e S u l l i v a n Mine a r e a compared t o t h o s e c a l c u l a t e d by McGarr a n d G r e e n (1978) f o r t h e E a s t Rand P r o p r i e t a r y mine. The l a c k of a c t i v i t y on any of t h e f a u l t s o u t s i d e t h e mine a r e a , l a c k of d e f i n i t e l i n e a t i o n s of a c t i v i t y w i t h i n t h e mine, o t h e r t h a n p o s s i b l y a l o n g c a v e e d g e s , and l a c k o f e v e n t s of any s i g n i f i c a n t m a g n i t u d e ( t h a t i s , m a g n i t u d e g r e a t e r t h a n t h e mine e x p l o s i o n s ) a l l s u g g e s t t h a t m i n i n g a c t i v i t y i s n o t a c t i n g as a t r i g g e r f o r any p r e - e x i s t i n g r e g i o n a l s t r e s s e s w h i c h would have t o be h o r i z o n t a l and c o m p r e s s i v e as d i s c u s s e d i n C h a p t e r 2. The g e o l o g i c e v i d e n c e d i s c u s s e d i n C h a p t e r 2 s u g g e s t s t h a t r e g i o n a l s t r e s s i n t h e v i c i n i t y o f t h e S u l l i v a n Mine i s e i t h e r n e u t r a l or e x t e n s i o n a l . ( F i g u r e 2.6 p a r t C, <r, v e r t i c a l ) w h i c h s u g g e s t s t h a t a c t i v i t y on t h e f a u l t s i n t h e f o o t w a l l w i l l i n f a c t be s u p p r e s s e d by m i n i n g . The a p p a r e n t c o r r e l a t i o n between m i c r o e a r t h q u a k e a c t i v i t y and p o r t i o n s o f t h e S u l l i v a n , Number-two, B u r c h e t t , A l p h a , B e t a and Hamlet f a u l t s i s due t o an e n t i r e l y d i f f e r e n t mechanism. I b e l i e v e t h a t o n l y t h e f a u l t p l a n e between t h e r o o f o f t h e mine w o r k i n g s and t h e . s u r f a c e i s 121 a f f e c t e d w i t h i n t h a t zone above t h e mine shown i n F i g u r e 2.5 i n w h i c h t h e i n d u c e d s t r e s s i s p r i m a r i l y t e n s i l e . Here t h e s t r e s s p a t t e r n c l e a r l y m a n i f e s t s i t s e l f i n t h e form of n o r m a l f a u l t i n g and c o l l a p s e i n c a v e a r e a s where t h e r o o f i s e i t h e r t o o weak or has a d d i t i o n a l s t r e s s e s p l a c e d on i t by p i l l a r r e m o v a l . The f a u l t s n e a r t h e edges of c a v e a r e a s r e p r e s e n t p l a n e s t h a t a r e e s s e n t i a l l y weaker t h a n t h e s u r r o u n d i n g r o c k and t h u s t e n s i o n a l f a i l u r e w i l l t e n d t o o c c u r p r e f e r e n t i a l l y a l o n g them. (v) The emergent e v e n t s r e m a i n a m y s t e r y . B a s e d on t h e i r c h a r a c t e r and t i m i n g however we now c a n s t a t e q u i t e d e f i n i t e l y what t h e y a r e n o t due t o ; t h i s o n l y l e a v e s a few r e a s o n a b l e p o s s i b i l i t i e s f o r t h e i r o r i g i n . The e a r l i e r s u g g e s t i o n , t h a t t h e y r e p r e s e n t m i n i n g t r i g g e r e d a c t i v i t y on t h e K i m b e r l e y f a u l t i s n o t i n k e e p i n g w i t h t h e s u g g e s t i o n t h a t r e g i o n a l s t r e s s a t t h e S u l l i v a n Mine i s e i t h e r n e u t r a l o r e x t e n s i o n a l : (a) Normal f a u l t i n g c a n n e v e r be i n d u c e d by u n l o a d i n g a l o n e i n t h i s c a s e and t h e K i m b e r l e y f a u l t i s a l s o c l e a r l y away from t h e c a v e a r e a s ; (b) T h r u s t o r s t r i k e s l i p f a u l t i n g t h a t i s t r i g g e r e d by m i n i n g would r e q u i r e t h e e x i s t e n c e o f a h o r i z o n t a l , c o m p r e s s i v e r e g i o n a l s t r e s s . . The emergent o n s e t and l o w e r f r e q u e n c y c o n t e n t o f t h e s e e v e n t s i n d i c a t e t h a t t h e y a r e n e i t h e r e x p l o s i o n e v e n t s nor sudden f a i l u r e t y p e e v e n t s . T h e i r s t r o n g c o r r e l a t i o n w i t h t h e w e e k l y m i n i n g c y c l e s u g g e s t s t h a t t h e y a r e m i n i n g r e l a t e d m i c r o e a r t h q u a k e s and i n v i e w of t h e i r a r r i v a l t i m e e r r o r s we c a n s u g g e s t t h a t t h e y t o o b e l o n g w i t h i n t h e mine a r e a . The o n l y two p o s s i b i l i t i e s l e f t a r e t h a t t h e y r e s u l t f r o m n o n - v i o l e n t 122 t e n s i o n a l d e f o r m a t i o n of a s l u m p i n g t y p e i n t h e h a n g i n g w a l l o r n o n - v i o l e n t s h e a r d e f o r m a t i o n ( i . e . " s t a b l e d e f o r m a t i o n " , M c Garr, 1971b) i n t h e immediate v i c i n i t y of t h e mine f a c e s . The r e s u l t s of t h i s s t u d y have s h e d much l i g h t on t h e n a t u r e and t i m i n g of m i c r o s e i s m i c i t y , and t h e r e g i o n a l and l o c a l i n f l u e n c e o f o r e e x t r a c t i o n a t t h e S u l l i v a n Mine . We a r e now aware o f t h e a r e a s of e x p e c t e d a c t i v i t y and have d i s c u s s e d t h e mechanisms i n v o l v e d . The use of m i c r o e a r t h q u a k e a c t i v i t y f o r t h e d e l i n e a t i o n o f f a u l t p l a n e s a t t h e S u l l i v a n Mine has f a i l e d , t h e i m p l i c a t i o n b e i n g t h a t r e g i o n a l s t r e s s c o n d i t i o n s a r e u n f a v o r a b l e f o r f a u l t r e a c t i v a t i o n , o t h e r t h a n i n t h e z o n e s o f t e n s i o n a l s t r e s s above t h e s t o p e a r e a s . In t h i s z o n e , f a u l t p l a n e s e x t e n d i n g f r o m t h e h a n g i n g w a l l t o t h e s u r f a c e may p o s s i b l y be d e l i n e a t e d w i t h i m p r o v e d p r o c e d u r e s , b u t i t i s a l s o t h e s e p o r t i o n s t h a t a r e e a s i l y a c c e s s i b l e and have a l r e a d y been mapped by v i s u a l i n s p e c t i o n . 7.1 FUTURE PROGRAMS The f o l l o w i n g s e c t i o n i s d e s i g n e d t o a i d f u t u r e s t u d i e s i n v o l v e d w i t h i n d u c e d m i c r o s e i s m i c i t y by s u g g e s t i n g v a r i o u s improvements t o combat t h e p r o b l e m s e n c o u n t e r e d d u r i n g t h e p r e s e n t s t u d y . C a r e f u l a t t e n t i o n s h o u l d be p a i d t o t h e g e o l o g i c e v i d e n c e i m p l y i n g t h e e x i s t e n c e , o r a b s e n c e , of a r e g i o n a l s t r e s s f i e l d when f o r m u l a t i n g t h e e x p e r i m e n t a l a i m s . The a r r a y d e s i g n and t i m i n g a s i t s t a n d s i s b a s i c a l l y n o t a c c u r a t e enough t o be u s e d as a p r e c i s e mapping t o o l and 123 r e c o m m e n d a t i o n s f o r m o d i f i c a t i o n s t o f u t u r e p rograms a r e as f o l l o w s : ( i ) H i g h A c c u r a c y C l o c k s : A common time b a s e a t a l l s t a t i o n s , w o u l d c o m p l e t e l y e l i m i n a t e t h e e r r o r s i n t r o d u c e d by t h e r m a l d r i f t o f t h e c r y s t a l c l o c k s . . T h i s would r e d u c e t h e t o t a l a r r i v a l t i m e e r r o r by a p p r o x i m a t e l y 50% i n t h e p r e s e n t s t u d y . ( i i ) H o r i z o n t a l Component S e i s m o m e t e r s : T h e s e would a l l o w t h e use o f p o l a r i t y i n f o r m a t i o n as d i s c u s s e d i n C h a p t e r 5 t h u s e n a b l i n g t h e d i s c r i m i n a t i o n between m i c r o e a r t h q u a k e s and e x p l o s i o n s and a l s o f a c i l i t a t i n g a f o c a l mechanism s t u d y . ( i i i ) Wide F r e q u e n c y P a s s b a n d : The d e s i r e d f r e q u e n c y p a s s b a n d w i l l v a r y d e p e n d i n g on t h e e x p e r i m e n t a l d e s i g n . T h e r e i s no p o i n t i n h a v i n g a h i g h upper f r e q u e n c y c u t f o r d i s t a n t s t a t i o n s due t o a t t e n u a t i o n o f t h e s i g n a l waveform, however f o r a s t a t i o n v e r y c l o s e t o t h e s o u r c e , i n a h i g h r e s o l u t i o n s t u d y , i t would be a d v a n t a g e o u s f o r t h e upper f r e q u e n c y l i m i t t o be c l o s e t o 100 Hz. t h i s w ould y i e l d e x t r e m e l y s h a r p f i r s t a r r i v a l s and p e r h a p s a l s o e n a b l e f r e q u e n c y d i s c r i m i n a t i o n between e x p l o s i o n and m i c r o e a r t h q u a k e e v e n t s . ( i v ) A r r a y C o n f i g u r a t i o n : The d e s i r e d a r r a y c o n f i g u r a t i o n w i l l a l s o v a r y , d e p e n d i n g on t h e a i m s o f t h e e x p e r i m e n t but i t i s c l e a r t h a t a t r u l y 124 3 - d i m e n s i o n a l a r r a y i s n e c e s s a r y t o a t t a i n t h e same l o c a t i o n a c c u r a c y i n f o c a l d e p t h as i n e p i c e n t r a l p o s i t i o n . Were a f u r t h e r e x p e r i m e n t t o be c o n d u c t e d a t t h e S u l l i v a n M i n e , t h e r e would be s e v e r a l m a j o r a r r a y d e s i g n c h a n g e s b a s e d on t h e f i n d i n g s of t h e p r e s e n t s t u d y : a: The o u t e r n e t c o u l d be c o l l a p s e d i n w a r d t o p r o v i d e a more d e t a i l e d c o v e r a g e of t h e mine area.. As no m i c r o e a r t h q u a k e s were r e c o r d e d o u t s i d e t h e mine a r e a d u r i n g t h e p r e s e n t s t u d y , t h e wide c o v e r a g e of t h e o u t e r n e t i s n o t n e c e s s a r y . b: As a r e s u l t of t h i s s t u d y , a r e a s of i n t e r e s t may be s e l e c t e d , and more s t a t i o n s s e t up i n s u r r o u n d i n g s t o p e s w i t h i n t h e mine. A s t a t i o n l o c a t e d on t h e s u r f a c e , d i r e c t l y above t h e a r e a of i n t e r e s t w ould a l s o a i d by p r o v i d i n g f u r t h e r c o n s t r a i n t on t h e f o c a l d e p t h s . In t h e c a s e o f f u r t h e r d e t a i l e d s u r v e y s i n t h e mine a r e a , and i f i t i s p o s s i b l e t o implement t h e above s u g g e s t i o n s , an e p i c e n t r a l l o c a t i o n a c c u r a c y o f a b o u t ± 20 m w i t h a b o u t ± 30 m i n d e p t h , as f o u n d by McGarr e t a l (1975) c o u l d be e x p e c t e d f o r t h e e v e n t s w i t h s h a r p f i r s t a r r i v a l s . 125 REFERENCES B e v i n g t o n > P.R. 1969. D a t a R e d u c t i o n a nd E r r o r A n a l y s i s f o r t h e P h y s i c a l S c i e n c e s , M c G r a w - H i l l Book Company, T o r o n t o . C e t e , A. 1977,. S e i s m i c s o u r c e l o c a t i o n i n t h e Ruhr d i s t r i c t . P r o c e e d i n g s of t h e F i r s t C o n f e r e n c e on A c o u s t i c E m i s s i o n / M i c r o s e i s m i c A c t i v i t y i n G e o l o g i c S t r u c t u r e s and M a t e r i a l s , P e n n s y l v a n i a S t a t e U n i v e r s i t y , J u ne 1975, T r a n s T e c h P u b l i c a t i o n s , C l a u s t h a l , Germany, pp. 231 - 241. Cook, N.G.W. 1963. The s e i s m i c l o c a t i o n o f r o c k b u r s t s , Rock M e c h a n i c s , (C. F a i r h u r s t , E d i t o r ) , P r o c e e d i n g s F i f t h Symposium on Rock M e c h a n i c s , Pergamon P r e s s , New Y o r k . pp. 493 - 516. Cook, N.G.W. 1976. S e i s m i c i t y a s s o c i a t e d w i t h m i n i n g . Eng. G e o l . , 10, pp. 99 - 122. Cumming, W.B., Cl o w e s , R.M., and E l l i s , R.M. 1979. C r u s t a l s t r u c t u r e f r o m a s e i s m i c r e f r a c t i o n p r o f i l e a c r o s s s o u t h e r n B r i t i s h C o l u m b i a . Can. J . E a r t h S c i . , 16, pp.. 1024 -1 040. E l l i s , R.M. 1977. I n v e s t i g a t i o n o f s e i s m i c a c t i v i t y a t S u l l i v a n mine. U n p u b l i s h e d r e p o r t f o r Cominco L i m i t e d . E t h i e r , V.G., C a m p b e l l , F.A., B o t h , R.A., and K r o u s e , H.R. 1976. G e o l o g i c a l s e t t i n g of t h e S u l l i v a n o r e b o d y and e s t i m a t e s o f t e m p e r a t u r e s and p r e s s u r e s o f metamorphism. E c o n . G e o l . , 71, pp. 1570 - 1588. F r a n t t i , G.E. 1977. S e i s m i s s i o n s and s u r f a c e waves r e l a t e d t o g e o l o g i c s t r u c t u r e s . P r o c e e d i n g s o f t h e F i r s t C o n f e r e n c e on A c o u s t i c E m i s s i o n / M i c r o s e i s m i c A c t i v i t y i n G e o l o g i c S t r u c t u r e s and M a t e r i a l s , P e n n s y l v a n i a S t a t e U n i v e r s i t y . , J u ne 1975, T r a n s T e c h P u b l i c a t i o n s , C l a u s t h a l , Germany, pp. 271 - 289. 126 Gough, D.I., and Gough, W.I. 1970. L o a d i n d u c e d e a r t h q u a k e s a t Lake K a r i b a - I I . Geophys. J . R. A s t r . S o c , 21, pp. 79 - 1 0 1 . G r e e n f i e l d , R . J . 1977. A m p l i t u d e s and s p e c t r a from u n d e r g r o u n d s o u r c e s . 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H a r d y , H.R.,Jr., and L e i g h t o n , F., E d i t o r s . 1977. P r o c e e d i n g s o f t h e F i r s t C o n f e r e n c e on A c o u s t i c E m i s s i o n / M i c r o s e i s m i c A c t i v i t y i n G e o l o g i c S t r u c t u r e s a n d ' M a t e r i a l s , P e n n s y l v a n i a S t a t e U n i v e r s i t y , J u ne 1975, T r a n s T e c h p u b l i c a t i o n s , C l a u s t h a l , Germany. Hoy, T. 1979. G e o l o g y o f t h e E s t e l l a - K o o t e n a y K i n g a r e a , s o u t h e a s t e r n B r i t i s h C o l u m b i a . B.C. M i n i s t r y o f E n e r g y , M i n e s and P e t r o l e u m R e s o u r c e s , P r e l i m i n a r y Map 36. Hoy, T., Edmunds, F.R., H a m i l t o n , J.M., H a u s e r , R.L., M u r a r o , T.W., and Ransom, P.W. 1981. L e a d - z i n c and c o p p e r - z i n c d e p o s i t s i n s o u t h e a s t e r n B r i t i s h C o l u m b i a . i n : F i e l d G u i d e s t o G e o l o g y and M i n e r a l D e p o s i t s . GAC/MAC/CGU C a l g a r y , 1981 A n n u a l M e e t i n g , pp. 41 - 67. Hoy, T. 1982. The P u r c e l l s u p e r g r o u p i n s o u t h e a s t e r n B r i t i s h C o l u m b i a ; s e d i m e n t a t i o n , t e c t o n i c s and s t r a t i f o r m l e a d - z i n c d e p o s i t s . i n : M a j o r S u l p h i d e D e p o s i t s o f -Canada and E n v i r o n s , t h e H.S. R o b i n s o n M e m o r i a l Volume, GAC ( i n p r e s s ) . 1 27 J u m i k i s , A.R. 1979. Rock M e c h a n i c s , F i r s t e d . T r a n s T e c h P u b l i c a t i o n s , C l a u s t h a l , Germany. K i s s l i n g e r , C. 1976. A r e v i e w o f mechanisms o f i n d u c e d s e i s m i c i t y . Eng. G e o l . , 10, pp. 85 - 98. L a h r , J . C . 1979. HYPOELLIPSE: A computer p r o g r a m f o r d e t e r m i n i n g l o c a l e a r t h q u a k e h y p o c e n t r a l p a r a m e t e r s , m a g n i t u d e , and f i r s t m o t i o n p a t t e r n . U.S. G e o l o g i c a l S u r v e y p r e l i m i n a r y r e p o r t . L e e , W.H.K. , and L a h r , J . C . 1972. HYP071.: A computer p r o g r a m f o r d e t e r m i n i n g h y p o c e n t e r , m a g n i t u d e , and f i r s t m o t i o n p a t t e r n o f l o c a l e a r t h q u a k e s . U.S. G e o l o g i c a l S u r v e y , open f i l e r e p o r t . L e i g h t o n , F., and B l a k e , W. 1970. Rock n o i s e s o u r c e l o c a t i o n t e c h n i q u e s . U.S. B u r e a u o f M i n e s , R e p o r t o f I n v e s t i g a t i o n , 7432. L e i g h t o n , F., and D u v a l l , W.I. 1972. A l e a s t s q u a r e s method f o r i m p r o v i n g r o c k n o i s e s o u r c e l o c a t i o n t e c h n i q u e s . U.S. B u r e a u o f M i n e s , R e p o r t o f I n v e s t i g a t i o n , 7626. M c C l a y , K. R. 1981. S t r u c t u r a l e v o l u t i o n o f t h e S u l l i v a n O r ebody, K i m b e r l e y , B.C. 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E d i t o r , F i r s t I n t e r n a t i o n a l Symposium on I n d u c e d S e i s m i c i t y , B a n f f , B.C., S p e c i a l I s s u e , I n d u c e d S e i s m i c i t y , Eng. G e o l . , 10., pp. 83 - 388. M i l n e , W.G., R o g e r s , G.C., R i d d i h o u g h , R.P., McMechan, G.P., and Hyndman, R.D. 1978. S e i s m i c i t y o f w e s t e r n Canada. Can. J . E a r t h S c i . , 15, pp. 1170 - 1193. Monger, J.W.H., and P r i c e , R.A. 1979. Geodynamic e v o l u t i o n of t h e C a n a d i a n C o r d i l l e r a - p r o g r e s s and p r o b l e m s . Can. J . E a r t h S c i . , 16, pp. 770 - 791. Monger, J.W.H., S o u t h e r , J.G., and G a b r i e l s e , H. 1972. E v o l u t i o n o f t h e C a n a d i a n C o r d i l l e r a . Am. J . of S c i . , 272, pp. 57.7 - 602. Mowrey, G.L., 1977. The f e a s i b i l i t y of m o n i t o r i n g m i c r o s e i s m i c a c t i v i t y f r o m a l o n g w a l l c o a l mine u s i n g n e a r - s u r f a c e t r a n s d u c e r s . M.Sc. T h e s i s , C o l l e g e o f E a r t h and M i n e r a l S c i e n c e s , P e n n s y l v a n i a S t a t e U n i v e r s i t y . Pomeroy, P.W., Simpson, D.W., and S b a r , M.L. 1976. E a r t h q u a k e s t r i g g e r e d by s u r f a c e q u a r r y i n g - t h e W a p p i n g e r s F a l l s , New York s e q u e n c e o f J u n e , 1974.. B u l l . S e i s m . S o c . Am, 66, pp. 685 - 700. P r i c e , R.A. 1977. An a n a l y s i s o f C e n o z o i c f a u l t d i s p l a c e m e n t s b a s e d on o f f s e t s o f o l d e r s t r u c t u r e s i n t h e C o r d i l l e r a o f s o u t h e a s t e r n B r i t i s h C o l u m b i a . Program w i t h A b s t r a c t s V o l . 2, GAC/MAC/CGU V a n c o u v e r , 1977, A n n u a l M e e t i n g , p. 42. Ransom, P.W. 1977. G e o l o g y o f t h e S u l l i v a n Orebody. i n : F i e l d t r i p G u i d e b o o k T r i p 1', L e a d Z i n c D e p o s i t s o f S o u t h e a s t e r n B r i t i s h C o l u m b i a , GAC/MAC/CGU V a n c o u v e r , 1977, A n n u a l M e e t i n g . pp. 7 - 2 1 . i 1 29 R i c e , H.M.A. 1937. C r a n b r o o k map a r e a , B.C. G e o l . S u r v . Can., Memoir 207. S c h o l z , C H . 1968. The f r e q u e n c y - m a g n i t u d e r e l a t i o n of m i c r o f r a c t u r i n g i n r o c k and i t s r e l a t i o n t o e a r t h q u a k e s . B u l l . S e i s m . S o c . Am., 58,. pp. 399 - 415. S e n t u r i o n S c i e n c e s I n c . 1971. A s e i s m i c i t y s t u d y o f t h e S u l l i v a n Mine a r e a , F i n a l R e p o r t t o Cominco L t d . Simpson, D.W. 1976. S e i s m i c i t y c h a n g es a s s o c i a t e d w i t h r e s e r v o i r l o a d i n g . Eng.. G e o l . , 10, pp. 123 - 150. S m i t h , R.B., W i n k l e r , P.L., A n d e r s o n , J.G., and S c h o l z , C H . 1974. S o u r c e mechanisms o f m i c r o e a r t h q u a k e s a s s o c i a t e d w i t h u n d e r g r o u n d mines i n e a s t e r n U t a h . B u l l . S e i s m . S o c . Am., 64, pp. 1295 - 1317. Snow, D.T. 1973. The g e o l o g i c , h y d r o l o g i c and g e o m o r p h i c s e t t i n g of e a r t h q u a k e s a t Lake K a r i b a . U n p u b l i s h e d p a p e r p r e s e n t e d a t C o n f e r e n c e on S e i s m i c E f f e c t s of R e s e r v o i r -Impounding, London. S p o t t i s w o o d e , S.M. 1980. S o u r c e mechanism s t u d i e s on W i t w a t e r s r a n d s e i s m i c e v e n t s . Ph.D. T h e s i s , U n i v e r s i t y of t h e W i t w a t e r s r a n d . Tatham, R.H. , Danbom, S.H., T y c e , R . C , and Omnes, G. 1980. S e i s m i c P a r a m e t e r s and t h e i r E s t i m a t i o n . Segment 6 i n The C o n v o l u t i o n a l M o d e l , an S.E.G. s c h o o l , D a l l a s . 130 APPENDIX 1 CLOCK DRIFT ERRORS We c o n s i d e r e r r o r s i n c l o c k t i m e s due t o v a r i a t i o n s i n t h e c r y s t a l f r e q u e n c y . L e t T = c l o c k t i m e ( s ) f = o s c i l l a t o r f r e q u e n c y (Hz) F = c o r r e c t o s c i l l a t o r f r e q u e n c y (Hz) Then a f t e r 1 s t h e c l o c k would show T = f / F More g e n e r a l l y , we c a n w r i t e T = f ( t ) d t C r y s t a l f r e q u e n c y e r r o r s a r e n o r m a l l y due t o ( i ) I n i t i a l o f f s e t A F (Hz) o ( i i ) t e m p e r a t u r e d r i f t A F T ( H z / ° C ) ( i i i ) a g i n g A F A ( H z / s ) Then T = — ( F + A F D + ' A F A T + A F A t ) d t A F A F ^ A F . .2 where A T - t e m p e r a t u r e change N o t e s : ( i ) F r e q u e n c y O f f s e t (AF ) The t erm i s l i n e a r and can t h e r e f o r e be e a s i l y c o r r e c t e d by t i m e c h e c k s d u r i n g t h e e x p e r i m e n t . 131 N o t e s : c o n t ' d ( i i ) A g i n g r a t e (AF^) F o r t h e G e o t e c h MCR-600 u n i t s t h e q u o t e d a g i n g r a t e i s 5 x 10 / y r (=1.369 x 1 0 _ 8 / d a y ) . i . e . t h e e r r o r p e r day = 1 .37 x 1 0 ~ 8 x 1 x 24 x 3600 = 1 m i l l i s e c o n d (ms) 2 T h i s i s n o t s i g n i f i c a n t . ( i i i ) T e m p e r a t u r e D r i f t ( A F ) F o r t h e G e o t e c h MCR-600 t h e quoted v a l u e i s 1 x 1 0 ~ 7 / ° C . L e t us assume t h a t t h e c r y s t a l s have been s e t i n a l a b o r a t o r y a t t e m p e r a t u r e T and a r e o p e r a t e d i n an e n v i r o n m e n t w i t h J_J t e m p e r a t u r e g i v e n by , . . 2TTt T + A s m 6 Lm ' " " 86400 AT = 1 x 1 0 " 7 t T L " ( T m = A S i n " 8 i ? u 0 " ) ] d t , - 7 r / x 86400 . 2-rrt = 1 x 10 7 [ ( T L - T m ) t = A c o s ~8540Q-F o r T = 2 5 ° C and u s i n g J u l y t e m p e r a t u r e v a l u e s f o r K i m b e r l e y o b t a i n e d f r o m E n v i r o n m e n t C a n a d a , T = 1 7 . 7 ° C and A = 9 .5 C , we have » , , „ - 7 o , 9 .5 x 86400 2-rrt ^ AT = 1 x 10 ( 7 . 3 t + 2^ C 0 S 8 6 4 0 0 _ ) T h i s g i v e s a l i n e a r d r i f t o f 63 m s / d a y w i t h a s i n e wave v a r i a t i o n o f 13 ms z e r o - t o - p e a k . We f u r t h e r n o t e t h a t i f t h e mean 132 ( i i i ) c o n t ' d t e m p e r a t u r e were 5 . 3 ° C t h e d r i f t r a t e w o u l d d e c r e a s e t o 46 m s / d a y . Thus i n c o m b i n a t i o n , t h e d i u r n a l t e m p e r a t u r e c y c l e and v a r i a t i o n s i n t h e mean d a i l y t e m p e r a t u r e may l e a d t o t i m i n g e r r o r s o f s e v e r a l 1 0 ' s o f ms. I n f u t u r e e x p e r i m e n t s , e i t h e r i m p r o v e d c r y s t a l s s h o u l d be u s e d o r t h e t e m p e r a t u r e s t a b i l i t y i m p r o v e d by t h e u s e o f t h e r m a l i n s u l a t i o n . 133 APPENDIX 2 HYPOCENTRE LOCATION Most l o c a l e a r t h q u a k e h y p o c e n t r e programs e . g . HYPOELLIPSE ( L a h r , 1979) a r e w r i t t e n f o r a 2 - d i m e n s i o n a l a r r a y o f s e i s m o g r a p h s w i t h v a r i a t i o n s i n e l e v a t i o n t a k e n i n t o a c c o u n t by t h e u s e o f s t a t i o n d e l a y s . F o r h y p o c e n t r e l o c a t i o n i n a m i n e e n v i r o n m e n t a t r u e 3 -d i m e n s i o n a l a r r a y o f s t a t i o n s i s g e n e r a l l y e m p l o y e d . A 3 - d i m e n s i o n a l c o m p u t a t i o n a l scheme i s t h e r e f o r e r e q u i r e d . The p r o g r a m used i n t h i s r e p o r t i s a m o d i f i e d v e r s i o n o f t h e code w r i t t e n by S p o t t i s w o o d e (1980) w h i c h i s s i m p l e i n c o n c e p t and c o m p u t a t i o n a l l y e f f i c i e n t . I t s b a s i s i s now d e s c r i b e d . The a r r i v a l t i m e s t ^ ( i = 1 , "*"N) o f c o m p r e s s i o n a l waves (P) and s h e a r waves (S) a r e o b s e r v e d a t s e i s m o g r a p h s l o c a t e d a t (x^, y ^ , z/) . I t i s assumed t h a t t h e P and S wave v e l o c i t i e s , a . and 8., t o e a c h x x' s t a t i o n a r e a l s o known. From t h i s d a t a we d e s i r e to f i n d t h e h y p o c e n t r e c o o r d i n a t e s (x , y , z ) and t h e o r i g i n t i m e t . N o r m a l l y more o o o b o J o b s e r v a t i o n s e x i s t t h a n unknown p a r a m e t e r s and one t h e r e f o r e d e s i r e s to m i n i m i z e an o b j e c t i v e f u n c t i o n , i n o u r c a s e t h e w e i g h t e d sum o f t h e s q u a r e s o f t h e d i s t a n c e r e s i d u a l s . Assume t h a t we have a t r i a l h y p o c e n t r e and o r i g i n t i m e x f c = ( x , y , z , t ) . Then t h e s t a t i o n h y p o c e n t r e d i s t a n c e s a r e g i v e n by d i = y ( x . - x ) 2 + ( y . - y ) 2 + ( z . - z ) 2 and t h e d i s t a n c e s b a s e d on t h e o r i g i n t i m e s a r e D . = a . ( t . - t ) px x px D . = B . ( t - t ) sx x s i 134 The d i s t a n c e r e s i d u a l s can t h e n be w r i t t e n R . = d . - D . pi x pi R . = d . - D . si 1 si and t h e w e i g h t e d sum o f t h e s q u a r e s o f t h e d i s t a n c e r e s i d u a l s ( t h e o b j e c t i v e f u n c t i o n ) i s N V R2 = L K . 2 (R . 2 + R . 2 ) . , i p i s i i = l where K_ i s a w e i g h t i n g f u n c t i o n I n t h e p r e s e n t p r o g r a m K . = a / ( b + d . ) I I i . e . a f u n c t i o n w h i c h l o w e r s t h e w e i g h t o f t h e more d i s t a n t s t a t i o n s . W i t h o u t d i f f i c u l t y , i t c o u l d be m o d i f i e d t o i n c l u d e t h e q u a l i t y o f t h e a r r i v a l t i m e p i c k . S e i d e l ' s method i s u s e d to d e t e r m i n e x = (x , y , z , t ) , — D o ' J o ' o ' o t h a t i s t h e v a l u e s o f 5 £ t w h i c h m i n i m i z e R2. O b s e r v a t i o n s a r e assumed to s a t i s f y w i t h i n measurement e r r o r an e q u a t i o n o f the f o r m . R ( x . , x ) = 0 ' T h e r e s i d u a l e q u a t i o n ' — l —o where x^ a r e t h e i n d e p e n d e n t v a r i a b l e s (known) x a r e t h e d e p e n d e n t v a r i a b l e s (unknown) . —o r 135 We may w r i t e t h e unknown t r u e h y p o c e n t r e and o r i g i n t i m e x^ i n t erms o f t h e t r i a l h y p o c e n t r e and o r i g i n t i m e x^ p l u s an unknown d i f f e r e n c e 6 x. The r e s i d u a l e q u a t i o n becomes R (x , x + 6x) = 0 E x p a n d i n g R i n T a y l o r ' s s e r i e s and n e g l e c t i n g q u a d r a t i c and h i g h e r o r d e r t e r m s 3R R = R ( x . , x j + 7 ~ I 6x i ' t L 3x 1 x — We now c h o o s e 6x t o m i n i m i z e N i = l T a k i n g p a r t i a l d e r i v a t i v e s and s e t t i n g e q u a l t o z e r o we o b t a i n A e q u a t i o n s 3R. 3R. N I l J -5— ( R . ( x . , xj + I -5— 6xJ = 0 3x^. 1 — 1 ' —t L 3x t t 1=1 t j t j = 1, . . . .A These e q u a t i o n s a r e t h e n s o l v e d s i m u l t a n e o u s l y f o r t h e unknown 62c w h i c h p r o v i d e an i m p r o v e d t r i a l s o l u t i o n . x ' = x + 6x t t T h i s p r o c e s s can be r e p e a t e d u n t i l Sx i s s u f f i c i e n t l y s m a l l . I n t h i s c a s e 136 HYPOCENTRE LOCATION PROGRAM 1 DIMENSION SKU(24),VEL(24),EVENT(3),ARTM(24),DF(4),SS(12),RR(4), 2 ; NARR(16),RES(16),DIS(16),XA(12),YA(12),ZA(12),SIN(9), 3 ;STN(5) 4 C 5 C**** T H I S PROGRAM WAS DEVELOPED BY S.M.SPOTTISWOOD 6 C DURING 1977 FOR LOCATING E.R.P.M. SEISMIC EVENTS 7 C SEIDELS METHOD OF SUCCESSIVE APPROXIMATIONS 8 C IS USED TO IMPROVE AN INITIAL GUESS LOCATION 9 C / 10 C 11 C TO COMPILE THIS PROGRAM...... 12 C 13 C RUN *FTN SCARDS=SPOTTI SPUNCH=SPOTTI.0 14 C 15 C TO RUN 16 C 17 C RUN SPOTTI.0+IMSL:8S 4 = SP0TTI.DATA 1 5=SP0TTI.DATA2 6=0UT1 7=OUT2 18 C 19 C WHERE 0UT2 IS THE INPUT FILE FOR 3DMAP 20 C 21 C**** MODIFICATIONS BY R.R.COENRAADS DURING 1981 FOR 22 C APPLICATION OF THE PROGRAM TO THE SULLIVAN MINE 2 3 C PROJECT ARE AS FOLLOWS ; 24 C - STATION COORDINATES AND EVENT LOCATIONS ARE 2 5 C IN FEET TO COMPLY WITH THE MINE COORDINATE 26 C GRID 27 C - UP TO 12 STATIONS ARE ACCEPTED 28 C - INPUT AND OUTPUT FORMAT MODIFICATIONS 29 C 30 REAL RDIR(6)/.028,-.071,.176,-.168,.420,1.0/ 31 LOGICAL LEAR, LDONE 32 DIST(X,Y,Z)=SQRT(X*X+Y*Y+Z*Z) 33 WRITE(6,201) 34 201 FORMATCl X',7X,'Y',7X,'Z HEAD SKEW*,4X,'P',6X,'S',7X, 3 5 1 'GEOPHONE') 36 DO 87 1 = 1 , 12 37 READ(4,10)XA(I),YA(I),ZA(I),SKU(I ) ,SKU(1 + 1 2) , 38 1 VEL(I),VEL(I+12),STN 39 Q************************ 40 C FEET CONVERSION 41 XA(I)=XA(I)*0.3048 42 YA(I)=YA(I)*0.3048 43 ZA(I)=ZA(I)*0.3048 44 Q*********************** * 45 10 FORMAT(3F6.0,2F5.3,2F5.3,5X,5A4) 46 C 10 FORMAT(5F5.0,2F5.3,5X,5A4) 47 C 48 C**** 12 GEOPHONES ARE USED FOR LOCATIONS 4 9 C LABELLED 1 TO 12 50 C (XA(I),YA(I),ZA(I ) , 1 = 1 ,10) ARE X Y Z COORDINATES IN METRES 51 C MINE COORDINATES ARE USED : X+ :WEST, 52 C Y+ :NORTH, 53 C Z+ :DOWN 54 C SKU(I ) ,I = 1 , 12 : HEAD SKEW CORRECTIONS APPLIED TO P ARRIVALS 55 C SKU(I) , 1=13,24 : HEAD SKEW CORRECTIONS APPLIED TO S ARRIVALS 56 C IN GENERAL SKU(I + 12)=SKU(I ) 57 C STATION RESIDUALS CAN BE INCORPERATED BY CHANGING 58 C P AND/OR S HEAD SKEW CORRECTIONS. 59 C VEL(I) , 1=1,12 : P VELOCITIES TO EACH GEOPHONE 60 C VEL(I) , 1=13,24 : S VELOCITIES TO EACH GEOPHONE 137 61 C 62 Q******** **************** 63 c METRES CONVERSION FOR WRITE 64 X A ( I ) = X A ( I ) / 0 . 3 0 4 8 65 Y A ( I ) = Y A ( I ) / 0 . 3 0 4 8 66 Z A ( I ) = Z A ( I ) / 0 . 3 0 4 8 67 W R I T E ( 6 , 2 2 ) X A ( I ) , Y A ( I ) , Z A ( I ) , S K U ( I ) , S K U ( 1 + 1 2 ) , 68 1 V E L ( I ) , V E L ( 1 + 1 2 ) , S T N 69 X A ( I ) = X A ( I ) * 0 . 3 0 4 8 70 Y A ( I ) = Y A ( I ) * 0 . 3 0 4 8 71 Z A ( I ) = Z A ( I ) * 0 . 3 0 4 8 72 Q*********************** * 73 87 CONTINUE 74 22 F O R M A T ( 3 F 8 . 0 , 2 F 7 . 3 , 2 F 7 . 2 , 5 X , 5 A 4 ) 75 ' NL INE=14 76 70 R E A D ( 5 , 1 3 , E N D = 9 9 , E R R = 9 9 ) E V E N T , S C A L , N P O O R 1 , N P O O R 2 , N D A Y , N H R S , M I : 77 +NSYM.NEV 78 1 3 F O R M A T ( 3 A 4 , F 4 • 1 , 2 I 2 , 4 X , I 3 , 1 X , I 2 , 1 X , I 2 , 3 X , I 2 , 1 6 X , I 3 ) 79 S C A L > 1 . 0 80 R E A D ( 5 , 1 4 , E N D = 9 9)ARTM 81 14 F O R M A T ( 1 2 F 6 . 3 ) 82 R E A D ( 5 , 1 5 ) 83 15 F O R M A T ( 1 X , / , 1 X ) 84 C 85 rj**** EVENT : EVENT T I T L E ; USUALLY DATE & T I M E . 86 C SCAL : PAPER SPEED OF HARD-COPY RECORD I N . M M / ( F l E L D ) SEC 87 C 88 C A R T M ( I ) , 1 = 1 , 1 2 : 12 P A R R I V A L S IN MM 89 C A R T M ( I ) , 1 = 1 3 , 2 4 : 12 S A R R I V A L S IN MM 90 C P & S A R R I V A L S ARE READ IN IN THE SAME ORDER AS 91 C - U S E D FOR GEOPHONE COORDINATES , V E L O C I T I E S & HEAD SKEWS 92 C NPOOR1 & NPOOR2 :GEOPHONE NUMBER (NPOOR=NPOOR+12 FOR S) 93 C OF UNCERTAIN A R R I V A L S 94 C NPOOR2 = 0 I F ONLY ONE A R R I V A L IS CONSIDERED UNCERTAIN 95 C NPOOR1 = 0 I F A L L A R R I V A L S HAVE BEEN READ WITH CONFIDENCE 96 NL INE=NLINE+12 97 I F ( N P O O R 1 . G T . 0 ) N L I N E = N L I N E + 8 98 I F ( N P O O R 2 . G T . 0 ) N L I N E = N L I N E + 8 99 C 100 C 101 C 1 02 C 1 03- C 1 04 I F ( N L I N E . G T . 1 1 5 ) N L I N E = 0 105 I F ( N L I N E . E Q . 0 ) W R I T E ( 6 , 6 6 0 - ) 106 660 F O R M A T ( ' 1 1 ) 107 66 I F ( N L I N E . N E . 0 ) W R I T E ( 6 , 6 6 1 ) 108 661 FORMAT(/// ) 109 c 1 10 c * * ** N L I N E IS USED TO S K I P TO A NEW PAGE OF OUT PUT 1 1 1 c NEAR THE END OF EVERY SECOND PAGE 1 1 2 c 1 1 3 W R I T E ( 6 , 2 0 ) E V E N T , N D A Y , N H R S , M I N , N E V 1 1 4 20 F O R M A T ( 2 X , 3 A 4 , 5 X , I 3 , 1 X , I 2 , ' : ' ,I 2 , 5 X , ' N U M B E R = ' , 1 3 , 1 1 5 +/ • ************* gx ' * * * * * * * * * ' 5x '************') ,1 16 W R I T E ( 6 , 1 7 ) A R T M 1 1 7 1 7 F O R M A T ( 1 X , 1 2 F 6 . 2 ) 1 18 I F ( S C A L . L E . O . ) G O TO 70 1 19 I F ( N P O O R 1 . G T . 2 4)NPOOR1= 0 120 I F ( N P O O R 2 . G T . 2 4 ) N P O O R 2 = 0 1 38 121 NNEW=0 122 TM=60000 1 23 C ARRIVAL TIMES ARE CONVERTED FROM MM TO MILLISECONDS 124 (2**** 1 25 C HEAD SKEW CORRECTIONS ARE ADDED 126 C EARLIEST ARRIVALS ARE IDENTIFIED 127 C 128 DO 1 1=1,24 129 IF(ARTM(I).EQ.0.)GO TO 1 1 30 ARTM(I)=1000.*(ARTM(I)/SCAL+SKU(I)) 131 IF(ARTM(I).GE.TM)GO TO 1 1 32 TM=ARTM(I) 133 M=I 1 34 1 CONTINUE 135 " 73 MM=M-12M (M-1 )/12) 1 36 Q** * THE FIRST (GUESS) LOCATION IS CHOSEN CLOSE TO THE 137 c** GEOPHONE AT WHICH FIRST ARRIVAL IS READ. 1 38 EVX=XA(MM)-40. 1 39 EVY=YA(MM) 140 EVZ=ZA(MM) 1 4 1 EVT=TM-60. 142 £**** THE ORIGIN TIME OF THE EVENT IS DETERMINED FROM EACH 143 GEOPHONE FOR WHICH BOTH P S. S ARRIVALS WERE READ. 144 DO 2 1=1,12 IF(ARTM(I+12).LE.0. .OR. ARTM(I).LE.0.) GOTO 2 145 1 46 VR=VEL(I+12)/VEL(I) 147 TO=(ARTM(I)-ARTM(1+12)*VR)/(1.-VR) 1 48 EVT=TO 1 49 WRITE(6,221) I, TO, ARTM(I), ARTM(I+12) 150 221 FORMAT(15,' , TO =',F7.0,2F8.0) 151 NLINE=NLINE+1 1 52 IF(TO.GT.TM) WRITE(6,222) M 1 53 222 FORMAT('+',35X,'THIS IS AFTER ARRIVAL',13) 1 54 2 CONTINUE 1 55 LDONE=.FALSE. 1 56 72 IT=0 1 57 LEAR=M.EQ.9 1 58 C 159 C 1 60 C 161 C 1 62 C*** THE ITERATIVE PROCEDURE USED FOR IMPROVING 163 C THE GUESS COORDINATES START HERE. 1 64 C FOR MOST EVENTS FEWER THAN SIX ITERATIONS ARE REQUIRED 165 C FOR SATIFACTORY CONVERGENCE. 166 C CONVERGENCE IS CONSIDERED TO BE SATISFACTORY IF THE MOVEMENT 167 C BETWEEN SUCCESSIVE ITERATIONS IS LESS THAN 1 METER. 168 7 1 IT=IT+1 1 69 Q* * * * ALL THE TERMS OF THE MATRICES SS AND RR 170 C (USED FOR IMPROVING THE LOCATION) ARE SET TO ZERO. 1 7 1 DO 161 J=1,12 1 72 161 SS(J)=0. 173 DO 1610 1=1,4 174 1610 RR(I)=0. 1 7'5 N = 0 176 NN = 0 1 77 C*** N ARRIVALS WERE READ. 178 C NN ARRIVALS ARE USED TO LOCATE THE EVENT DURING EACH PASS. 179 C (N-3 <= NN <= N) 180 ERROR= 0. 139 181 WMAX=0. 182 DO 164 1=1,24 183 IF(ARTM(I).EQ.0.) GOTO 164 1 84 IF(N.EQ.15) GOTO 164 185 c*** NO MORE THAN 15 ARRIVALS ARE USED. 186 N=N+1 187 11=1 - 1 2 * ( ( 1 - 1 ) / l 2 ) 188 X=EVX-XA(II) 189 Y=EVY-YA(II) 190 Z=EVZ-ZA(II) 191 D=DIST(X,Y,Z) 192 IF(IT.GE.3 .AND. I.EQ.M .AND. D.GT.5000.) LEAR=.TRUE. 193 W=VEL( I ) 1 94 P VELOCITIES ARE FIXED AT 6.1 KM/SEC. 195 C S VELOCITIES ARE FIXED AT 3.8 KM/SEC FOR DISTANT EVENTS. 196 IF (LEAR) W=6.1 -2 . 3* {I/I I ) 197 fj* * * * W : DISTANCE RESIDUAL = (THEORETICAL-OBSERVED) DISTANCE 198 c FROM EVENT TO GEOPHONE, METERS. 1 99 W=D+(EVT-ABS(ARTM(I)))*W 200 NARR(N)=ISIGN(I,IFlX(ARTM(I))) 201 RES(N)=W/W 202 IF(I .EQ.NPOOR1) RES 1=W 2C3 IF(I .EQ.NPOOR2) RES2-W 204 DIS(N)=D 205 IF(ARTM(I).LT.0.) GOTO 164 206 NEGATIVE ARRIVAL TIMES ARE NOT USED FOR LOCATIONS 207 NN=NN+1 208 ARRIVALS FROM CLOSE GEOPHONES ARE GIVEN A GREATER EMPHASIS 209 c THAN ARRIVALS FROM MORE DISTANT GEOPHONES. 210 c THE WEIGHTING FACTOR USED HERE (WT) IS CHOSEN 21 1 c TO BE CONSISTENT WITH ERRORS IN VELOCITIES 212 c TO EACH GEOPHONE AND ERRORS IN PICKING ARRIVALS. 213 WT=l0000./(600.+D) 214 WW=ABS(W)*WT 215 £**** THE LEAST CONSISTENT ARRIVAL IS IDENTIFIED. 216 IF(WMAX.GT.WW) GOTO 170 2 1 7 IMAX=I 2 1 8 WMAX=WW 2 1 9 1 70 ERROR=ERROR+W*W 220 DF(I),I=1,3 ARE THE DIRECTIONAL COSINES 221 c FROM EACH (IMPROVED) LOCATION TO EACH GEOPHONE. 222 DF(1)=X/D 223 DF(2)=Y/D 224 DF(3)=Z/D 225 DF(4)=W 226 f j * * * * RR(I),I=1,4 t SS(I),I=1,10 ARE THE COEFFICIENTS OF THE 227 c MATRICIES USED TO CALCULATE THE CORRECTION FACTOR USED TO 228 c IMPROVE THE LOCATION. 229 JK = 0 230 DO 165 J =1 ,4 RR(J)=RR(J)+DF(J)*W*WT 231 232 DO 165 K=1,J 233 JK=JK+1 234 165 SS(JK)=SS(JK)+DF(J)*DF(K)*WT 235 1 64 CONTINUE 236 IF(NN.GT.2) GOTO 166 237 EVENTS WITH ONLY 3, 4, OR 5 READ ARRIVALS ARE LOOSELY 238 C CONSTRAINED 239 c TO 100 M. ABOVE (HERCULES) REEF. 240 W=EVZ-4 554.-.168*EVX+.4 20*EVY 140 241 - RR(1)=RR(1)-.168*W 242 RR(2)=RR(2)+.420*W 243 RR(3)=RR(3)+W 244 CCCCCCCCC 245 CCC 246 C 247 DO 167 JK=1,6 248 167 SS(JK)=SS(JK)+RDIR(JK) 249 NN=NN+1 250 N=N+1 251 NARR(N)=999 252 RES(N)=W 253 DIS(N)=W 254 IF(NN.LT.4) GOTO 70 255 c**** LEQT1P IS A SUBROUTINE IN THE INTERNATIONAL MATH AND 256 C AND STAT LIBRARY IMSL. 2 57 C LEQT1P SOLVES THE EQUATION A*X=B. 2 58 C WHERE A IS AN N BY N MATRIX STORED IN SYMMETRICAL STORAGE 2 59 C MODE, AND B IS AN M BY M MATRIX. 260 C FOR THIS PROGRAM N=4 AND M=1. 261 166 CALL LEQT1P(SS, 1, 4,'RR, 4, IGDT, DI, D2, IER) 262 C**** THE AMOUNT OF MOVEMENT DURING EACH SUCCESSIVE ITERATION 263 C IS RESTRICTED BY "FIX". THIS GUARDS AGAINST OSCILLATORY 264 C BEHAVIOUR SOMETIMES FOUND USING SEIDELS METHOD. 265 FIX=1.2-FLOAT(IT)/20. 266 EVX=EVX-RR(1)*FIX 267 EVY=EVY-RR(2)*FIX 268 EVZ=EVZ-RR(3)*FIX 269 EVT=EVT-RR(4)*FIX 270 IF(NN.EQ.4)GO TO 185 271 ERROR=SQRT(ERROR/(NN-4.0)) 272 185 IF(NN.EQ.4)ERROR=0.0 273 D=DIST(RR(1),RR(2),RR(3)) 274 c**** EVENT IS CONSIDERED TO DIVERGE IF ITERATION IS >5 KM. 275 IF(D.GT.5000.) GOTO 999 27 6 C**** EVENT IS CONSIDERED TO CONVERGE IF ITERATION IS <1 M. 277 IF(D.GT.1.0 .AND. IT.LE.30) GOTO 71 278 IF(LEAR) WRITE(6,220) 279 220 FORMAT(' VELOCITIES OF 6.1 AND 3.8 KM/SEC USED') 280 C 281 C****** EVX,EVY & EVZ ARE THE MINE COORDINATES OF THE EVENT LOCATION 282 C EVT IS THE ORIGIN TIME RELATIVE TO THE COMMON REFERENCE TIME 283 C ON THE HARDCOPY RECORD IN MILLISECONDS 284 C ERROR = SQRT((SUM OF SQUARES OF DISTANCE RESIDUALS IN METERS 285 C /(NUMBER OF ARRIVALS USED FOR LOCATION - 4)) 286 C************************ 287 C METRES CONVERSION FOR WRITE 288 EVX=EVX/0.3048 289 EVY=EVY/0.3048 290 EVZ=EVZ/0.3048 291 EVT1=EVT/1000. 292 WRITE(6,21)EVX,EVY,EVZ,EVT1,ERROR 293 C TEMPORARY OUTPUT FILE ADDITION 294 WRITE(7,990)EVENT,NDAY,NHRS,MIN,EVT1,NEV 295 990 FORMAT(1X,3A4,2X,1 DAY',1X,I3,2X,I2,':',I2,':',F5.2,8X,' NUMBER 296 WRITE(7,991)EVX,EVY,EVZ,NSYM,NN,ERROR 297 991 FORMAT(3F8.0,4X,'PLOT SYMBOL = ',12,5X,'ARRIVALS = ',I2,3X,'ERR 298 +F5.0,/,1X) 299 EVX=EVX*0.3048 300 EVY=EVY*0.3048 ^ 141 301 EVZ=EVZ*0.3048 3Q2 f j * ********************** * 303 21 FORMATC0X =',F7.0,', Y =',F7.0,', Z =',F7.0,', T =',F7.3, 304 1 ', ERROR =',F5.0) 305 IF(IT.GT.6)WRITE(6,25)IT 306 25 FORMAT('+',60X,'OVER',13,' ITERATIONS') 307 IF(D.GT.1.0)WRITE(6,250)D 308 250 FORMAT(41X,'DIST MOVED LAST ITER',F6.0,' METRES') 309 C 310 C****** NARR(N) : GEOPHONE NUMBER OF NTH ARRIVAL 311 C (N = 13 TO 24 FOR S ARRIVALS) 312 C IF(NARR.LT.0).ARRIVAL IS NOT USED FOR THIS LOCATION 313 C NARR = 999 EVENT IS LOOSELY CONSTRAINED TO 100M ABOVE(HERCU 314 C REEF 315 WRITE(6,26)NN,(NARR(I),1=1,N) 316 26, FORMAT(/,I3,' ARRIVALS ', 1617) 317 C 318 C RES :(THEORETICAL - OBSERVED) ARRIVAL TIME ,MSEC 319 C 320 WRITE(6,27)(RES(I),1=1,N) 321 27 FORMAT(' RESIDUALS '.16F7.0) 322 C 323 C**** DIS(I) = HYPOCENTRAL DISTANCE BETWEEN GEOPHONE I AND 324 C EVENT LOCATION 325 C 326 C************************ 327 C METRES CONVERSION FOR WRITE 328 DO 37 1=1,N 329 DIS(I)=DIS(I)/0.3048 330 37 CONTINUE 331 WRITE(6,28)(DIS(I),1=1,N) 332 DO 38 1=1,N 333 DIS(I)=DIS(I)*0.3048 334 38 CONTINUE 335 Q************************ 336 28 FORMAT(' DISTANCE ',16F7.0) 337 IF(NPOOR1.EQ.0)GO TO 171 338 C 339 C**** UNCERTAIN ARRIVAL TIMES ARE MADE NEGATIVE AND THE LOCATION 34 0 C IS REPEATED WITHOUT THEM 341 C IF TWO ARRIVALS ARE UNCERTAIN IE NPOOR.NE.O 342 C LOCATION IS REPEATED FIRST WITHOUT THE UNCERTAIN ARRIVAL 343 C WHICH HAS THE LARGER TIME RESIDUAL. 344 C 345 IF((NPOOR2.EQ.0).OR.(ABS(RES 1).GT.ABS(RES2)))GO TO 129 346 ARTM(NPOOR2)=-ARTM(NPOOR2) 347 WRITE(6,29)NPOOR2 34 8 2 9 FORMAT('0' ,'RELOCATE WITHOUT DOUBTFUL ARRIVAL',I 3) 349 NPOOR2=0 350 GOTO 72 351 129 ARTM(NPOOR1)=-ARTM(NPOOR1) 352 WRITE(6,29) NPOOR1 353 NPOOR1=NPOOR2 354 NPOOR2=0 355 GOTO 72 356 171 CONTINUE 3 57 IF(NNEW.NE.O) GOTO 173 358 C**** DOUBTFUL OR BADLY INCONSISTENT ARRIVALS ARE TESTED TO SEE 359 C IF THEY COULD HAVE BEEN PICKED AS THE INCORRECT PHASE. 360 C IF SO, THE LOCATION IS REPEATED WITH THE 'CORRECTED' DATA. 14 2 361 DO 172 1 = 1 ,N 362 NOLD=-NARR(l) 363 IF(NOLD.LE.O) GOTO 172 364 II=ISIGN(1, 21-2*NOLD) 365 IF(ABS(11*DIS(I)/RES(I)+10.5).GT. 2.0) GOTO 172 366 NNEW=NOLD+12*II 367 ARTM(NNEW)=-ARTM(NOLD) 368 ARTM(NOLD)=0. 369 WRITE(6,272) NOLD, NNEW 370 272 FORMAT('0','TRY ARRIVAL', 13, ' AS ARRIVAL', 13) 371 GOTO 72 372 172 CONTINUE 373 173 CONTINUE 374 GO TO 70 375 C IF((WMAX.LT.600.).OR. LDONE .OR. (NN.LE.6)) GOTO 70 376 C**** IF ANY ARRIVAL IS INCONSISTENT BY MORE THAN ABOUT 50 M 37 7 C (AT 1 KM) COMPARED TO THE EXPECTED LOCATION, 378 C A FURTHER LOCATION IS DONE WITHOUT IT. 379 LDONE=.TRUE. 380 WRITE(6,23) IMAX 381 23 FORMATC0', '****', 13, ' ???? ****') 382 ARTM(IMAX)=-ARTM(IMAX) 383 NLINE=NLINE+8 384 GOTO 72 385 999 WRITE(6,24) IT 386 24 FORMAT(40X,'DIVERGES AFTER' ,13, ' ITERATIONS') 387 C************************ 388 C METRES CONVERSION FOR WRITE 389 EVX=EVX/0.3048 390 EVY=EVY/0.3048 391 EVZ=EVZ/0.3048 392 EVT1=EVT/1000. 393 WRITE(6,21) EVX, EVY, EVZ, EVT1, ERROR 394 C TEMPORARY OUTPUT FILE ADDITION 3 95 WRITE(7,990)EVENT,NDAY,NHRS,MIN,EVT1,NEV 396 WRITE(7,991)EVX,EVY,EVZ,NSYM,NN,ERROR 397 EVX=EVX*0.3048 398 EVY=EVY*0.3048 399 EVZ=EVZ*0.3048 400 C************************ 401 WRITE(6,26) NN, (NARR(I),I=1,N) 402 IF(NPOOR1.EQ.0) GOTO 70 403 C**** DIVERGENT LOCATIONS ARE REPEATED WITHOUT UNCERTAIN ARRIVALS. 404 ARTM(NPOOR1)=-ARTM(NPOOR1) 405 WRITE(6,29) NPOOR1 406 NPOOR1=NPOOR2 407 NPOOR2=0 408 GOTO 73 409 99 STOP 410 END End of F i l e 143 TEST EXAMPLE T l OPEN P I T BLAST X Y Z HEAD SKEW p s GEOPHONE 4068. 9705. 3936. 0.0 0. 0 5.30 3.06 1 . D39 5710. 13000. 2727 . 0.0 0. 0 5.30 3.06 2. D27 1515. 3905. 4385. 0.0 0. 0 5.30 3.06 3. NCN 2455. 13810. 5343 . 0.0 0. 0 5.30 3.06 4. PMP 11145. 3945. 3715. 0.0 0. 0 5.30 3.06 5. MOR 5840. 7482. 4287 . 0.0 0. 0 5.30 3.06 6. NAD 8637. 12706. 4346. 0.0 0. 0 5.30 3.06 7. LOI 8133. 16860. 5482 . 0.0 0. 0 5.30 3.06 8. SUL - 1 5990. -850. 4190. 0.0 0. 0 5.30 3.06 9. MAT -5060. 12185. 4630. 0.0 0. 0 5.30 3.06 10.MRK - 1 4339. 16421. 5457. 0.0 0. 0 5.30 3.06 11.BOG 2908. 7690. 4638 . 0.0 0. 0 5.30 3.06 12.PIT EVENT(5):29 ************ 46.89 0.0 0.0 0.0 172 21 : 5 NUMBER = 75 ********* ************ 0.0 0.0 47.32 46.95 47.24 47.40 48.04 47.43 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 46.96 0.0 X = 4074 . , Y = 8495. 3392., T = 46.835, ERROR = 241.OVER 13 ITERATIONS 8 ARRIVALS RESIDUALS DI STANCE 1 22. 1 326. 5 6 7 8 9 10 12 -1. 13. -43. -12. 69. -24. -16. 8415. 2223. 6282. 9529. 22148. 9928. 1885. 

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