Open Collections

UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

A re-examination of the August 22, 1949 Queen Charlotte earthquake Bostwick, Todd Kendall 1984-12-31

You don't seem to have a PDF reader installed, try download the pdf

Item Metadata

Download

Media
831-UBC_1984_A6_7 B68.pdf [ 6.54MB ]
Metadata
JSON: 831-1.0052501.json
JSON-LD: 831-1.0052501-ld.json
RDF/XML (Pretty): 831-1.0052501-rdf.xml
RDF/JSON: 831-1.0052501-rdf.json
Turtle: 831-1.0052501-turtle.txt
N-Triples: 831-1.0052501-rdf-ntriples.txt
Original Record: 831-1.0052501-source.json
Full Text
831-1.0052501-fulltext.txt
Citation
831-1.0052501.ris

Full Text

A RE-EXAMINATION OF THE AUGUST 2 2 , 1949 QUEEN CHARLOTTE EARTHQUAKE by TODD KENDALL BOSTWICK B.A., The U n i v e r s i t y  Of C a l i f o r n i a ,  1979  A THESIS SUBMITTED I N PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES DEPARTMENT OF GEOPHYSICS AND ASTRONOMY  We a c c e p t t h i s  t h e s i s as conforming  to the required  standard  THE UNIVERSITY OF B R I T I S H COLUMBIA July  ©  Todd K e n d a l l  1984  B o s t w i c k , 1984  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  requirements f o r an advanced degree at the  the  University  o f B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make it  f r e e l y a v a i l a b l e f o r reference  and  study.  I further  agree t h a t p e r m i s s i o n f o r e x t e n s i v e 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 o f  department or by h i s or her  representatives.  my  It i s  understood t h 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  permission.  Department of The U n i v e r s i t y of B r i t i s h 1956 Main Mall Vancouver, Canada V6T 1Y3  DE-6  (3/81)  Columbia  written  i i  Abstract Using recorded were  previously  unavailable  at Sitka, Alaska,  determined  earthquake  thirty-eight  f o r the  (Ms=8.1).  horizontal  August  new a f t e r s h o c k  22,  The a f t e r s h o c k  1949  z o n e was  f r o m 300 km t o t h e n o r t h o f t h e e p i c e n t e r epicenter,  yielding  aftershock to  the  exist.  a  total  Queen found  distribution  the  rupture  the  n o r t h , and then t o t h e south  extend  t o 190 km s o u t h  of the  z o n e o f 490 km.  (Rogers,  directivity at three  rupture  propagating  velocity  between  between  the  function  stations. to  3.1 km/s  and  1983) d o e s n o t  clustering  differential  results  phases  imply  a  3.5  km/s.  length  and t h e a f t e r s h o c k  that the r a d i a t i o n fault  length  does  length.  l e n g t h and t h e r u p t u r e  displacement  o f f s e t along  displacement  occurring  fault  The  not  fault  length  rupture  zone  implies  the  full  of the r a d i a t i o n  suggests  that  the  was u n e v e n , w i t h t h e l a r g e s t  t h e z o n e i n d i c a t e d by t h e r a d i a t i o n  length. An a t t e m p t was made t o d e r i v e t h e m e c h a n i s m  the  were  difference  represent  non-equivalence  the fault in  to  unilateral  The  radiation  fault  first  . n o r t h w e s t f o r 265 km a t a  and  gap  of the e p i c e n t e r .  The  the  This  suggests a time v a r i a t i o n of  sequence, with the a f t e r s h o c k s  analyzed  fault  Charlotte to  aftershock  o f t h e Ms=8.1 e a r t h q u a k e  The a f t e r s h o c k  rupture  locations  zone i m p l i e s t h a t a p r e v i o u s l y s u g g e s t e d s e i s m i c  north  The  seismograms  two  largest aftershocks  radiation  patterns.  technique  to obtain  I t was  using  their azimuthal  concluded  f o c a l mechanism  solutions for  that  the  surface use  of  wave this  solutions i s ineffective for  i ii  this and  area  and  the q u a l i t y  time  in history  when s t a t i o n  of i n s t r u m e n t c a l i b r a t i o n s  coverage  poor.  was  sparse  iv  Table of Contents Abstract L i s t of Tables L i s t of Figures Acknowledgement  i i vi v i i x  Chapter I INTRODUCTION 1 1.1 THE QUEEN CHARLOTTE FAULT 1 1.1.1 T e c t o n i c S e t t i n g Of The Queen C h a r l o t t e F a u l t ....1 1.1.2 S e i s m i c i t y Of The Queen C h a r l o t t e F a u l t 6 i . Epicenter Locations 6 i i . F o c a l Mechanisms ..8 1.1.3 F a u l t M o d e l 9 1.2 THE 1949, M 8.1, QUEEN CHARLOTTE EARTHQUAKE 11 1.2.1 F o c a l M e c h a n i s m 12 1.2.2 S e i s m i c Gap 14 1.3 THESIS OBJECTIVES 16 Chapter I I AFTERSHOCK ZONE OF THE 1949 QUEEN CHARLOTTE EARTHQUAKE ...19 2 . 1 PROCEDURE 19 2.2 RESULTS 27 Chapter I I I SURFACE WAVE ANALYSIS 3.1 POINT SOURCE MECHANISM SOLUTION 3.1.1 I n t r o d u c t i o n 3.1.2 T h e o r y A n d Computer P r o g r a m s 3.2 RUPTURE PARAMETERS 3.2.1 I n t r o d u c t i o n 3.2.2 D i r e c t i v i t y F u n c t i o n T h e o r y 3.2.3 D i f f e r e n t i a l P h a s e s T h e o r y 3.3 PROCESSING 3.3.1 D a t a A c q u i s i t i o n 3.3.2 D a t a P r o c e s s i n g 3.3.3 A m p l i t u d e D a t a 3.3.4 P h a s e D a t a  ;  Chapter IV RESULTS FOR THE M=8.1 EARTHQUAKE OF AUGUST 22 4.1 D I R E C T I V I T Y FUNCTION 4.2 D I F F E R E N T I A L PHASES 4.3 ERROR ANALYSIS 4.4 S E I S M I C MOMENT AND STRESS DROP  34 34 34 35 41 41 42 44 46 46 48 49 51 52 59 65 68 69  Chapter V RESULTS FOR THE EARTHQUAKES OF AUGUST 23 AND OCTOBER 31 ..74 MECHANISM SOLUTIONS 87  V  Chapter VI SUMMARY AND DISCUSSION 6.1 DISCUSSION 6.2 CONCLUSION  94 94 99  BIBLIOGRAPHY APPENDIX A - L I S T OF SEISMOGRAPH STATIONS  101 .106  APPENDIX B - WORLD AVERAGED PHASE V E L O C I T I E S AND Q VALUES  108  APPENDIX C - EARTH MODEL USED FOR THE AUGUST 23 AND OCTOBER 3 1 MECHANI SM SOLUTIONS ....110 APPENDIX D - INSTRUMENT RESPONSE CURVES  111  vi  List  of Tables  I.  PUBLISHED FAULT PLANE SOLUTIONS FOR EARTHQUAKES ON THE QUEEN CHARLOTTE FAULT 8  II.  AFTERSHOCK DATA  22  III.  D I F F E R E N T I A L PHASE FAULT LENGTHS  66  IV.  RUPTURE LENGTH FROM D I R E C T I V I T Y AND D I F F E R E N T I A L PHASES  95  V.  ESTIMATE OF SEISMIC SOURCE PARAMETERS OF THE 1949 QUEEN CHARLOTTE EARTHQUAKE  100  vi i  List  of F i g u r e s  1. TECTONIC SETTING OF THE QUEEN CHARLOTTE FAULT  1  2. RECENT TECTONIC HISTORY OF THE QUEEN CHARLOTTE FAULT ..3 3. DIRECTION OF RELATIVE PLATE MOTION  4  4. MODEL OF THE QUEEN CHARLOTTE FAULT ZONE  5  5. S E I S M I C I T Y OF THE QUEEN CHARLOTTE REGION  7  6. STRUCTURAL INTERPRETATION OF A REFRACTION SURVEY ACROSS THE QUEEN CHARLOTTE FAULT ZONE 10 7. P-NODAL MECHANISM SOLUTION FOR THE AUGUST 2 2 , 1949 QUEEN CHARLOTTE EARTHQUAKE 13 8. PROPOSED SEISMIC GAPS ON THE QUEEN CHARLOTTE FAULT ...15 9. AFTERSHOCK LOCATIONS  23  10. RELATIONSHIP OF THE CHATHAM STRAIT AND FAIRWEATHER FAULTS TO THE QUEEN CHARLOTTE FAULT  26  11. TIME DISTRIBUTION OF AFTERSHOCKS  27  12. EMPIRICAL MAGNITUDE RUPTURE-LENGTH RELATIONSHIP FOR 7 REGIONS OF THE WORLD 29 13. MAGNITUDE RUPTURE-AREA RELATIONSHIPS  30  14. TIME PROGRESSION OF AFTERSHOCKS  33  15. D I G I T I Z E D TUO SEISMOGRAMS FOR THE AUGUST 22 EARTHQUAKE (M=8.1) 54 16. D I G I T I Z E D PAS AND HON SEISMOGRAMS FOR THE AUGUST 22 EARTHQUAKE (M= 8.1)  55  17. TYPICAL GROUP VELOCITY CURVES FOR LOVE AND RAYLEIGH WAVES  56  18. GROUP VELOCITY CURVES FOR THE AUGUST 22 DATA  57  19. GROUP VELOCITY CURVES FOR THE AUGUST 22 DATA  58  20. D I R E C T I V I T Y FUNCTION CURVES  60  2 1 . DECAYING SOURCE D I R E C T I V I T Y FUNCTION CURVES  62  vi i i  22. THE EFFECT OF BILATERAL RUPTURE ON THE D I R E C T I V I T Y FUNCTION 23. LEAST SQUARES SOLUTION TO THE DATA 24. RESPONSE CURVE FOR THE PAS STRAIN METER  63 ..64 70  25. D I G I T I Z E D SEISMOGRAMS FOR THE AUGUST 23 EARTHQUAKE (M=6.4)  .75  26. D I G I T I Z E D SEISMOGRAMS FOR THE AUGUST 23 EARTHQUAKE (M=6.4)  76  27. D I G I T I Z E D SEISMOGRAMS FOR THE OCTOBER 31 EARTHQUAKE (M=6.2)  77  28. D I G I T I Z E D SEISMOGRAMS FOR THE OCTOBER 31 EARTHQUAKE (M=6.2)  78  29. D I G I T I Z E D SEISMOGRAMS FOR THE OCTOBER 31 EARTHQUAKE (M=6.2)  79  30. GROUP VELOCITY CURVES FOR THE AUGUST 23 LOVE WAVE DATA  80  3 1 . GROUP VELOCITY CURVES FOR THE AUGUST 23 RAYLEIGH WAVE DATA 81 32. GROUP VELOCITY CURVES FOR THE AUGUST 23 S J P DATA  82  33. GROUP VELOCITY CURVES FOR THE OCTOBER 31 LOVE WAVE DATA 83 34. GROUP VELOCITY CURVES FOR THE OCTOBER 31 LOVE WAVE DATA 84 35. GROUP VELOCITY CURVES FOR THE OCTOBER 31 RAYLEIGH WAVE DATA 85 36. GROUP VELOCITY CURVES FOR THE OCTOBER 31 RAYLEIGH WAVE DATA 86 37. THEORETICAL LOVE WAVE RADIATION PATTERN FOR THE AUGUST 23 EARTHQUAKE 88 38. THEORETICAL RAYLEIGH WAVE RADIATION PATTERN FOR THE AUGUST 23 EARTHQUAKE  89  39. THEORETICAL LOVE WAVE RADIATION PATTERN FOR THE OCTOBER 31 EARTHQUAKE 90 40. THEORETICAL RAYLEIGH WAVE RADIATION PATTERN FOR THE OCTOBER 31 EARTHQUAKE  91  i.x  4 1 . FOCAL MECHANISMS OF THE AUGUST 23 AND OCTOBER 31 EARTHQUAKES  92  42. DISPLACEMENT ALONG THE SAN ANDREAS FAULT FOR THE 1906 EARTHQUAKE 96  X  Acknowledgement  This  research  provided  owes much  the  to  original  direction  a l s o obtained  SIT  Ellis,  provided  thesis. this  He  surrogate A  most  Dr.  I  Ian J o n e s , and,  Financial Agreement  computer  Ellis's  goes  to  My  Rogers then  Dr.  gave  Rogers  advisor,  Dr.  programs used i n  this  i n the development  valuable  support  of  as  my  thesis  and  sabbatical leave.  a l l  Rogers,  who  read  Dr.  t o t h a n k Don  most i m p o r t a n t l y , my  my  Ellis,  and  Dr.  W h i t e , Dave M a c k i e ,  wife Kimiko,  f o r making  my  enjoyable.  support  by  f o r me.  povided  would a l s o l i k e  288/83  R e s o u r c e s , and  Dr.  Dr.  i t s development.  useful direction  C l o w e s , Dr.  t i m e i n Canada so  Rogers.  f o r t h e t h e s i s , and  records  the  Clowes  thanks  improved i t : Dr. Armstrong.  of  advisor during  special  during  seismic  also provided  thesis.  Garry  suggestion  e n c o u r a g e m e n t and the  Dr.  from  f o r t h i s p r o j e c t was the  Department  NSERC O p e r a t i n g  provided  of  G r a n t A2617.  Energy,  by  Research Mines  and  I. 1.1  THE QUEEN CHARLOTTE FAULT  1.1.1  Tectonic  S e t t i n g Of The Queen C h a r l o t t e  The Queen C h a r l o t t e Queen the  INTRODUCTION  Charlotte  boundary  plates  Islands  Fault  Zone a l o n g  i s a transform  between t h e P a c i f i c  Fault  t h e west  coast  f a u l t making  and N o r t h A m e r i c a n  of  the  up p a r t of lithospheric  (see Figure l ) .  Figure  1 - TECTONIC SETTING OF THE QUEEN CHARLOTTE FAULT  Geographic features, tectonic setting and key seismograph stations ( S I T a n d V I C ) i n t h e Queen C h a r l o t t e I s l a n d s r e g i o n (adapted from Rogers, 1 9 8 3 ) .  The  fault  zone  extends  northwestward  from  a  ridge-trench-  2  transform to  junction  fault  {Von Huene e t .  also  known  as  a l . , 1979).  Jordan  primarily  and  mid-ocean  Chichagof-  motions  ridge  of  spreading  r i g h t - l a t e r a l s t r i k e - s l i p a t a r a t e o f 5.5  discussion The  (1978)  the  i n Riddihough, fault  escarpments. submarine  terrace  between  which  b a s i n t o the west.  Minster rates, i s  cm/yr  (see  shows two d i s t i n c t  fault  1977).  zone c h a r a c t e r i s t i c a l l y Wedged  Islands  Current motion along  f a u l t , as d e t e r m i n e d from g l o b a l p l a t e  and  the  s o u t h o f t h e Queen C h a r l o t t e  s o u t h e r n A l a s k a where i t i s  Baranof the  triple  is  the  two  escarpments  e l e v a t e d more t h a n  lies  a  1 km a b o v e t h e  Riddihough et a l .  (1980) h a v e p r o p o s e d  that  p r e s e n t c o n f i g u r a t i o n of the f a u l t  zone d e v e l o p e d a b o u t  1 Ma  a g o , when a t r i p l e Explorer  Ridge,  j u n c t i o n , then l o c a t e d  at  the  end  of  jumped n o r t h w e s t e r l y t o t h e D e l l w o o d K n o l l s i n  r e s p o n s e t o c h a n g i n g s p r e a d i n g c o n d i t i o n s of t h e E x p l o r e r This l e d to r i f t i n g beginning  of  position Queen  of  spreading  Hyndman and E l l i s  escarpment,  with  older  fault  ocean  crust  (4.5  suggested  junction to  the  what outer  that  plates prior  this  Ridge.  and  the  knolls.  change  in  r e q u i r e d a l a n d w a r d jump o f t h e is Queen  now  seen  as  Charlotte  accommodating the t r a n s c u r r e n t m o t i o n between North American  Ma)  a t the newly c r e a t e d D e l l w o o d  (1981) h a v e  of t h e t r i p l e  Charlotte  the  t o t h e jump 1 Ma  the ago  the  inner  fault  scarp  Pacific  and  ( s e e F i g u r e 2)..  3  Figure  2 - RECENT TECTONIC HISTORY OF THE QUEEN FAULT  CHARLOTTE  Schematic r e c o n s t r u c t i o n o f p l a t e t e c t o n i c d e v e l o p m e n t r e l e v a n t t o t h e Queen C h a r l o t t e I s l a n d s r e g i o n f o r t h e p a s t 1 Ma. AM, the North American plate; EX, t h e Explorer plate; PA, t h e P a c i f i c p l a t e . S i n g l e l i n e s with opposing arrows represent t r a n s f o r m m a r g i n s and t h e d i r e c t i o n o f s l i p ; d o u b l e l i n e 3 r e p r e s e n t s p r e a d i n g margins; and t o o t h e d l i n e s r e p r e s e n t c o n v e r g i n g m a r g i n s w i t h t e e t h o n t h e o v e r r i d i n g p l a t e . A t 1 Ma note the d i f f e r e n c e between the r e l a t i v e motion vector and t h e t r a c e o f t h e transform fault between Explorer Ridge and Delwood Knolls. This gives rise to instability o f the t r i p l e junction and t h e t r a n s f o r m f a u l t and l e a d s t o a s y m m e t r i c s p r e a d i n g . A t 0.5-1 Ma s p r e a d i n g a t T u z o Wilson Knolls begins. This requires the transform motion between PA a n d AM t o jump l a n d w a r d i n t o o l d e r c r u s t , w h i c h i s t h e n p u s h e d n o r t h w a r d w i t h PA. T h e i n s t a b i l i t y a t D e l w o o d Knolls causes readjustment of Explorer R i d g e a n d t h e t r a n s f o r m f a u l t j o i n i n g t h e two ( a f t e r R i d d i h o u g h e t a l . , 1 9 8 0 ; Hyndman a n d E l l i s , 1 9 8 1 ) .  (From Horn e t . a l . , 1 9 8 4 ) .  4  In of  the present c o n f i g u r a t i o n  the inner f a u l t  trace l i e s  relative  motion  Pacific  and  region.  The a n g l e o f t h i s  American  n o r t h e r n end o f t h e f a u l t a l o n g Moresby I s l a n d  zone,  plates  for  (1978) between the  oblique interaction  i s small  but i n c r e a s e s towards  could occur compressive  by  at  the  t h e s o u t h e r n end  (see f i g u r e 3 ) .  3 - DIRECTION OF RELATIVE PLATE MOTION  The a n g l e o f p l a t e convergence  the  Queen C h a r l o t t e  The relative motion arrows show the motion P a c i f i c P l a t e r e l a t i v e t o the North American (adapted from Rogers 1983).  of  the bearing  10° t o 20° west o f t h e c a l c u l a t e d  v e c t o r o f M i n s t e r and J o r d a n  North  Figure  of t h e f a u l t  interaction  suggests  t h e r e i s an e l e m e n t  i n t h e Queen C h a r l o t t e r e g i o n . oblique  deformation  subduction of  the  a d j a c e n t a r e a s , o r some c o m b i n a t i o n  of Queen  the  The  Pacific  Charlotte  of both  of the• Plate  (Perez  convergence plate  or  I s l a n d s and and  Jacob,  5  1980) . To  account  for  t h e c o n v e r g e n c e , Hyndman and E l l i s  h a v e s u g g e s t e d an u n d e r t h r u s t Hyndman  et  al.  (1982),  model,  subsequently  f o r t h e Queen C h a r l o t t e  (1981)  refined fault  zone.  They s u g g e s t o b l i q u e s u b d u c t i o n c o u l d be a c c o m p l i s h e d f i r s t s e r i e s o f s t r i k e - s l i p e a r t h q u a k e s , t h e n by until  c o u p l i n g between  great  that  oblique  faulting  As t h e p l a t e  i n time the f a u l t i n g  Figure  Deformation Front  4 - MODEL OF THE  is  must jump s e a w a r d  edge o f t h e c o n t i n e n t a l c r u s t  Q.C.Troug!  Thus,  by  this  o c c u r s i n the o c e a n i c l i t h o s p h e r e  beneath the c o n t i n e n t a l margin.  the  i s so  i t exceeds the s t r e n g t h of the o c e a n i c l i t h o s p h e r e ,  transcurrent  intervals  by a  convergence  t h e o v e r r i d i n g and u n d e r l y i n g p l a t e  and a n o t h e r s e r i e s o f s t r i k e - s l i p e v e n t s o c c u r s . model,  by  subducted, t o remain  (see f i g u r e 4 ) .  Terrace  Coast  Q.C. Islands  QUEEN CHARLOTTE FAULT ZONE  A p o s s i b l e t e c t o n i c model o f t h e Queen C h a r l o t t e f a u l t zone. The oblique convergence i s resolved into s t r i k e - s l i p m o t i o n p a r a l l e l t o t h e m a r g i n on t h e Queen Charlotte fault and a small component of underthrusting perpendicular t o the margin (from Hyndman e t a l . , 1 9 8 2 ) .  at near  6  1.1.2 S e i s m i c i t y Of The Queen C h a r l o t t e F a u l t The  Queen  a c t i v e areas earthquake  of  Canada.  (MS=8.1)  Charlotte Fault occurred  in  earthquakes southern,  C h a r l o t t e r e g i o n i s one o f t h e most  is  Indeed,  which  the  Canada.  occurred  recorded  Besides  the  o f t h e Queen  earthquake  1949  event,  to  have  three  Ms^7 the  one i n 1972 (Ms=7.6)  and t h e o t h e r  end o f t h e f a u l t  i n 1970 (Ms=7.0)  (see Figure 5 ) .  s o l u t i o n s of earthquakes  region  (1975),  and  epicenter  Rogers  locations  seismographs  and  Sykes  (1968),  (1983). have  In  e v e n t s o f m a g n i t u d e M >5.0  been  limited  (1983), data  after  Charlotte  fault  suggests  North American  by  and  Savino  the  accuracy  of  the  scarcity  of  1965  1965. a  detailed  from  evaluation  scarp with l i t t l e ,  of  i f any,  the  zone, has c o m p i l e d  1900 t o 1980 ( s e e F i g u r e  shows a s t r o n g c o r r e l a t i o n  5).  w i t h t h e i n n e r Queen seismicity  t h a t a t p r e s e n t most, i f not a l l , p l a t e motion  groups of  Epicenter uncertaintyfor  f o r t h e Queen C h a r l o t t e f a u l t  a s e i s m i c i t y map o f t h e a r e a seismicity  Charlotte  i s ±50 km f o r most e v e n t s b e f o r e  ±25 km f o r most e v e n t s a f t e r  seismicity  Queen  Kelleher  general,  operating i n the region.  Rogers  i n the  h a v e been o b t a i n e d by t h r e e p r i n c i p a l  i n v e s t i g a t o r s : Tobin  This  Charlotte  Epicenter Locations  Islands  The  i n the middle  e n d o f t h e Queen C h a r l o t t e F a u l t ,  Epicenter  and  Queen  h a v e o c c u r r e d s i n c e 1900, one i n 1929 (Ms=7) a t  the southern i.  1949  largest  a t t h e n o r t h e r n end of t h e f a u l t , near  the  seismically  inland.  of the P a c i f i c -  i n t h i s area occurs along the  Queen  7  Charlotte  Figure  fault.  5 - S E I S M I C I T Y OF THE QUEEN CHARLOTTE REGION  E p i c e n t e r l o c a t i o n s f r o m 1900 t o 1980. Through the years the t h r e s h o l d magnitude r e q u i r e d f o r earthquake d e t e c t i o n h a s d r o p p e d f r o m M >7 between 1900-1917, t o M >6 b e t w e e n 1917-1948, t o M >5.0 between 1948-1980 (adapted from Rogers, 1983).  8  ii.  Focal  Mechanisms  A l l p u b l i s h e d f o c a l mechanisms f o r e a r t h q u a k e s C h a r l o t t e F a u l t Zone a r e l i s t e d i n T a b l e 1.  T a b l e I - PUBLISHED FAULT PLANE SOLUTIONS FOR ON THE QUEEN CHARLOTTE FAULT  1 927 Oct 1 949 Aug  24 22  1 949 Oct  31  1958 1 970 1 970 1 972 1 972 1 972 1 973 1 973 1 976  Jul Jun Jun Jul Aug Aug Jul Jul Feb  10 24 24 30 04 15 01 03 03  The  l o c a t i o n and o r i e n t a t i o n o f t h e Queen  relative  defined  the  P-nodal  constrained  and  1970  distribution  size  mechanism  of  of t h e P - n o d a l  because  (see F i g u r e  it 7).  bisects  earthquake  fault  thrust strike-slip strike-slip strike-slip strike-slip thrust strike-slip thrust strike-slip str i ke-slip  Fault  seismographs for  which  the  is  network  But t o a c c u r a t e l y  usually of  define  the  1983).  and  the  August  22,  region  1949  well The well  azimuth  l a r g e enough t o r e c o r d Islands  has  California  well in  the  p l a n e s o l u t i o n s a r e those f o r the June  (Ms=7),  (Ms=8.1), ( R o g e r s ,  strike-slip  h a v e been o b t a i n e d .  f a u l t plane  T h u s , i n t h e Queen C h a r l o t t e  defined  of  strike-slip  Charlotte  earthquakes  solutions  d i p , t h e e a r t h q u a k e s must be  Europe. well  global  l i m i t e d the  southern extension  stations  EARTHQUAKES  S t a u d e r , 1 9 5 9 ; W i c k e n s a n d Hodgson,1967 H o d g s o n and M i l n e , 1 9 5 1 ; W i c k e n s and H o d g s o n , 1 9 6 7 ; R o g e r s , 1983 Hodgson and S t o r e y , 1 9 5 4 ; W i c k e n s and Hodgson,1967 S t a u d e r 1960; W i c k e n s a n d Hodgson,1967 C h a n d r a 1 974; R o g e r s , 1983 C h a n d r a 1 974 C h a n d r a 1 974; P e r e z and J a c o b , 1 9 8 0 C h a n d r a 1 974 P e r e z and J a c o b , 1 9 8 0 Chandra,1974; P e r e z and Jacob,1980 C h a n d r a , 1 9 7 4 ; P e r e z and J a c o b , 1 9 8 0 W e t m i l l e r and H o r n e r , 1 9 7 8 ; R o g e r s , 1983  to  effectively  i n t h e Queen  only 24,  earthquake  9  The  mechanism  (Chandra of  solution  motions of Minster Perez  fault  and J a c o b  (1978) or  Gulf  of A l a s k a  the  northern  end  of  region,  at the southern with predicted  Chase  (1980) s t u d i e d  the eastern  relative  i s consistent  and J o r d a n  in  end plate  (1978)  f o r the  19 f a u l t p l a n e  solutions  four  t h e Queen C h a r l o t t e  of which o c c u r r e d fault.  on  The s e n s e o f  p l a t e m o t i o n c a l c u l a t e d from t h e s e e a r t h q u a k e mechanism  solutions also motion  t h e J u n e 24, 1970 e a r t h q u a k e  1974; R o g e r s , 1983) w h i c h o c c u r r e d  t h e Queen C h a r l o t t e  area.  for  corresponds  of the a r e a .  to  the  predicted  relative  These f a u l t p l a n e s o l u t i o n s imply  p r e d i c t e d p l a t e motions f o r  the  area  of  Minster  plate  that the  and  Jordan  ( 1 9 7 8 ) o r C h a s e (1978) a r e c o r r e c t . 1.1.3 F a u l t . An  i n s i g h t i n t o t h e c r o s s - s e c t i o n a l s t r u c t u r e o f t h e Queen  Charlotte across al.  fault  (1984).  pervasive Charlotte block  zone h a s been p r o v i d e d  Their  faults  separated  The  rock  consistent  by  the  units with  section  depths  c o n t i n e n t a l block  than  to the east.  those  and  undisturbed  three  crustally  outer  oceanic  had lower  the  The d e p t h t o  18 km b e l o w s e a l e v e l , i m p l y i n g  shows  Queen  m a k i n g up t h e w e s t e r n m o s t  of  s e c t i o n of the t e r r a c e b l o c k  survey  by H o r n e t  two m a j o r  inner  u n i t s composing t h e t e r r a c e block  equivalent  crustal  blocks  corresponding to  faults.  zone d i s c u s s e d  interpreted structure  crustal  had v e l o c i t i e s  The r o c k  to  by t h e r e f r a c t i o n  the southern h a l f of the f a u l t  distinctive  at  Model  velocities  ocean b l o c k the  increased  crust.  base  or the of  i n depth from  the 12  an e a s t w a r d d i p o f 20° i n t h e  10  Moho. the  The i n n e r  fault  c o n t i n e n t a l block  Figure  separating  This  profile  across  block  a p p e a r e d t o be d i p p i n g w e s t w a r d  6 shows t h e s t r u c t u r a l  (1984).  the t e r r a c e  unit  from  60°-80°.  i n t e r p r e t a t i o n o f by Horn e t a l .  i n t e r p r e t a t i o n i s also consistent with a gravity the area. Distance  (km)  80  w 100  Figure 6 - STRUCTURAL INTERPRETATION OF A REFRACTION SURVEY ACROSS THE QUEEN CHARLOTTE FAULT ZONE The f i r s t number i n t h e v e l o c i t y stratigraphy gives the v e l o c i t y a t t h e t o p o f t h e u n i t , a n d t h e s e c o n d number g i v e s t h e v e l o c i t y a t t h e b o t t o m o f t h e same u n i t , a l i n e a r g r a d i e n t b e i n g a s s u m e d . R L F , L o u s c o o n e I n l e t f a u l t ; S C B , S a n Cristoval b a t h o l i t h ( t h e dashed vertical lines within unit 4 show the surface e x p r e s s i o n o f t h i s b a t h o l i t h ) ; QCF, Queen C h a r l o t t e f a u l t ; a n d EX2 s h o w s the l o c a t i o n of the p e r p e n d i c u l a r marine p r o f i l e .  (From Horn e t a l . , 1984) .  11  The the  r e s u l t s o f Horn e t a l .  results  of  Hyndman  and  (1984) a r e a l s o c o n s i s t e n t Ellis  (1981).  m i c r o e a r t h q u a k e a c t i v i t y a l o n g t h e Queen for the  a t e n d a y p e r i o d , Hyndman a n d E l l i s seismicity  vertical  I n a study of t h e  Charlotte (1981)  associated  with  the  to  landward  s c a r p ; t h e o u t e r s c a r p showed no a c t i v i t y .  fault  zone  found almost a l l  t o be l o c a t e d a l o n g what a p p e a r e d  fault  with  be  a  near  or inner  fault  The o b s e r v e d maximum  e a r t h q u a k e d e p t h was 21 km. U s i n g t h e h e a t f l o w r e s u l t s o f Hyndman e t a l . thermal  elastic  arguments,  Hyndman  and  estimated the depth i n the c r u s t of the roughly  corresponds  instability to the  this  submarine  area.  t o be a b o u t  of earthquake a c t i v i t y  Moho f r o m H o r n e t a l .  On Sunday A u g u s t (local  time),  strong  earthquake.  Queen sinking  isotherm,  which seismic  basin,  16 km f o r  the  (A=6.0°)  22,  1949  the  observed  and w i t h t h e depth of t h e  EARTHQUAKE  at  Queen  Charlotte  The  earthquake,  and  Jasper  are  into the P a c i f i c  wondering ocean";  approximately Islands felt  (A=7.0°)  Newspapers r e p o r t e d t h a t  Charlottes  with  i nthe  (1984).  1.2 THE 1949, M 8.1, QUEEN CHARLOTTE  excitement.  also  They f o u n d t h e d e p t h  8 km f o r t h e o c e a n  well  and  (1981)  t e r r a c e a n d 35 km f o r t h e c o n t i n e n t a l c r u s t  depth  Whitehorse  600°C  f r a c t u r e can occur.  These r e s u l t s agree r e a s o n a b l y  maximum  Ellis  t o the depth i n the c r u s t t o which  or b r i t t l e  boundary  (1981)  i f their  were s h a k e n as  f a r away  caused  "Nervous  9:00  P.M. by a as  considerable  r e s i d e n t s of  the  islands are slowly  " S m a l l i s l a n d s have d i s a p p e a r e d  12  i n some s p o t s , and the  new  i s l a n d s have appeared  recent earthquakes  the  Queen  o f f B.C.  Charlotte  coast".  region  are  n e w s p a p e r r e p o r t s and  provide a  1949  Earthquake.  Queen C h a r l o t t e  1.2.1  first  Milne The  vividly  colorful  s e i s m i c hazards  illustrated  by  introduction  in  these  to  f o c a l m e c h a n i s m of t h i s e a r t h q u a k e  m o t i o n o f P waves h a v e b e e n o b t a i n e d and  Hodgson  n i n e l a r g e s t a f t e r s h o c k s have (1968),  and  s t r i k e of the  earthquake the  f o r the  (1951), . Wickens  Sykes The  The  following  the  F o c a l Mechanism Solutions  the  in others  focal  corresponds  and  well  principally component  mechanism  strike-slip  horizontal different If  (15°) the  1980)  along  the  earthquake, The  for  the  The with  coupled 7).  during  d i p of  Tobin  August  However this  the  July  and  the  i m p l y , then Queen not  24,  (1983). 22,  of the f a u l t  there  the motion a l o n g  the  fault  a  very  small  the d i r e c t i o n is  thrust  of t h e  Charlotte  taken  fault  up by t h a t  c o n v e r g e n c e m i g h t be  component at the  net  significantly area.  mechanism  (Chandra,  Alaska earthquakes  is a  at  very  earthquake  southern  1949  is  earthquake  1970  and  fault  with  the  and  (1983).  from the p r e d i c t e d p l a t e m o t i o n s f o r the  1983)  Jacob,  by  p l a t e i n t e r a c t i o n models are c o r r e c t , as  s o l u t i o n s of Rogers,  Figure  motion  Rogers  located  e x a c t l y w i t h the s t r i k e  constrained,  (see  been  and  Hodgson  more r e c e n t l y , r e l o c a t e d by R o g e r s  l a t i t u d e of the e p i c e n t e r .  steep  (1967),  by  using  of  1974;  (Perez  and  convergence,  l a t i t u d e of the  1949  earthquake.  taken  into  account  in  several  13  ways.  One p o s s i b i l i t y  earthquake  i s different  break as i n d i c a t e d Convergence two  largest  (M=6.2).  i s that  could  by  first  period  motion  of  the motion of the i n i t i a l motion  be p a r t i a l l y  a f t e r s h o c k s on A u g u s t  23  A l t e r n a t i v e l y , t h i s could  s l i p earthquakes predicted and E l l i s  from  the  also  the long  mechanism  and  of the  October  be one o f t h e l a r g e  by t h e p r e v i o u s l y  first  solution.  t a k e n up i n e i t h e r (M=6.4)  the  mentioned  strikeHyndman  (1981) model. S.TH A  S  Figure  31  7 - P-NODAL MECHANISM SOLUTION FOR THE AUGUST 2 2 , 1949 QUEEN CHARLOTTE EARTHQUAKE  August 22, 1949, mechanism s o l u t i o n l o w e r h e m i s p h e r e projection. P o s i t i o n o f k e y s t a t i o n s a r e i n d i c a t e d on the f o c a l sphere (Adapted from Rogers, 1983).  14  1.2.2 S e i s m i c  Gap  K e l l e h e r and S a v i n o  (1975) h a v e p o i n t e d o u t t h e p o s s i b i l i t y  of a s e i s m i c gap t o t h e n o r t h o f t h e A u g u s t 2 2 , 1949 (see  Figure  8).  earthquake  The u n c e r t a i n t y comes f r o m w h e t h e r t o c o n s i d e r  as a f t e r s h o c k s an e v e n t l o c a t e d n e a r 56°N on A u g u s t 2 3 , 1949 and two  earthquakes  (M=6.25 a n d 5.5) a l s o n e a r 56°N t h a t o c c u r r e d  O c t o b e r 3 1 , 1949, more t h a n two months a f t e r  t h e main shock.  the northern-most events a r e a f t e r s h o c k s , t h e r u p t u r e 470  km, a n d no s e i s m i c gap e x i s t s ;  i f not the rupture  a b o u t 300 km, a n d a s e i s m i c gap d o e s Although  no d e f i n i t e c r i t e r i a  length  on If is  length i s  exist. have  been  established  for  identification  of aftershocks at t e l e s e i s m i c d i s t a n c e s , K e l l e h e r  (1972),  when  studying  consider  an e v e n t an a f t e r s h o c k  months  after  the  more f r o m o t h e r would  not  South  American  mainshock  aftershocks.  be c o n s i d e r e d  i f i t occurred  and  1978) s u p p o r t  L3) r e c o r d e d  By  these  a  fault  as a f t e r s h o c k s and t h e s h o r t e r  rupture  seismic  recently, gap  The r e s u l t s  interpretation.  length  of  Rogers  does not e x i s t .  Using  of  L o v e waves (L2  a t Pasadena,  Ben-Menahem 22,  f u n c t i o n (Ben-Menahem and  p h a s e s (Ben-Menahem, 265  Ben-Menahem  v e l o c i t y of t h e August  the d i r e c t i v i t y  v e l o c i t y o f 3.5 km/sec t o t h e Most  two  events  T o k s o z , 1962) a n d d i f f e r e n t i a l obtained  than  these  l e n g t h and r u p t u r e  earthquake using  more  criteria  on t h e EW s t r a i n - m e t e r  derived the f a u l t 1949  this  zones, d i d not  o r i f i t was i s o l a t e d by 50 km o r  l e n g t h o f 300 km w o u l d be f a v o r e d . (1965,  rupture  1961).  km a n d a u n i l a t e r a l  He  rupture  northwest. (1984),  has  suggested  His conclusion  i s based  that  the  primarily  15  on an e x a m i n a t i o n o f t h e S I T (A=4.0°) r e c o r d s f o r t h e two months following of  the  1949 e a r t h q u a k e .  12-16 s e c o n d s  which would  He n o t e d s e v e r a l S-P  intervals  p l a c e them i n t h e d i s t a n c e  range o f  the s e i s m i c gap.  Figure  8 - PROPOSED SEISMIC GAPS ON THE QUEEN CHARLOTTE FAULT  M a j o r e a r t h q u a k e s a l o n g t h e Queen C h a r l o t t e F a u l t zone and t h e e x t e n t o f t h e i r a f t e r s h o c k s . Shaded circles a r e p o o r e r s o l u t i o n s (adapted from Rogers 1983).  Rupture  length  magnitude-rupture pointed  out  can  length  that  also  be  estimated  relationships.  often-quoted  from  Rogers  empirical  (1983)  magnitude-rupture  has length  16  relationships 300  km  t o 470  aftershock The seismic one  give estimates km  s u g g e s t e d by  the  two  shorter  of a b o u t  Tocher  event  150  km.  ( 1 9 5 8 ) and  would  approximately is  4.5  that  of  Thus, the  Hence t h e  important  the  zone l e a v e s  Iida  (1979) s u g g e s t a m a g n i t u d e  amount o f  strain that could  by c o n s t a n t Victoria  plate  motion  seismograph  X 5.5  approximately  a  7have  since  station  cm/yr) (Rogers, 7-3/4  magnitude  released during a complete rupture or  not,  f o r e v a l u a t i o n of s e i s m i c  of  risk  a  to  (Rogers,  seismic  i n the  is  1983).  s t o r e d s t r a i n w o u l d a p p e a r t o be e q u a l  existence,  a  during  l e n g t h r e l a t i o n s h i p s of  (84 y e a r s  to  e x p e c t e d t o be  1983).  The  the  meters  equivalent  earthquake.  Acharya  s e i s m i c gap  establishment  This  of  I f t h i s were a l l t o r u p t u r e  occur.  been s t o r e d i n t h e the  r a n g e of  interpretations  i n t e r p r e t a t i o n of the a f t e r s h o c k  earthquake, the magnitude-fault  3/4  the  zone.  gap  (1965),  1.3  w h i c h more t h a n c o v e r  gap  is  region.  THESIS OBJECTIVES As  Queen  indicated Charlotte  understanding  in  this  earthquake  the  tectonic  Islands region.  With t h i s  earthquake  undertaken.  was  introduction, plays  an  dynamics  t h e A u g u s t 22,  important in  the  role  were  in  Queen C h a r l o t t e  i n mind, a c l o s e r examination There  1949  three  of  the  parts to  this  investigation. 1).  The  investigation records  aftershock of  the  zone  was  aftershock  from the S i t k a s e i s m i c  re-examined.  A  detailed  z o n e became p o s s i b l e when  station  (SIT)  were  found  the  after  17  having the  been l o s t  epicenter  epicenter This  as  (A=4.0°)  the  allowed  f o r many y e a r s . lying  next nearest  e a r t h q u a k e s as  the a f t e r s h o c k  SIT  was  half  the  again  station  as  close  in Victoria  s m a l l as M >2.8  z o n e as c o m p a r e d t o  closest station  M >4.5  to  (VIC,  to the  A=8.1°).  t o be  used t o  when  only  define  VIC  was  available. 2) .  To  determined  from  phases,Love Tucson  improve  the  the  waves  reliability  directivity  L 2 , L 3 , and  (TUO), H o n o l u l u  was  (HON), and  done  due  o f p h a s e and  t o a) c o m p l e x i t y  of  and  surface  w a v e s , was  the  c)  directivity  and  (PAS)  be  w i t h i n a narrow 3) . were  (M=7.5), showed t h a t  the  between  f u n c t i o n and  source,  b)  interference  to l a t e r a l  with  body  Aki's  waves and  results  differential  averaging  the  heterogeneity  of  the  higher  mode  indicated  that  phase r e s u l t s d e r i v e d that  r e s u l t s of  better  results  several stations  azimuth.  to  help  F o r w a r d m o d e l i n g was radiation patterns theoretical  of  the  Mechanism s o l u t i o n s of  sought  evaluated  azimuth  significant.  by  were  at  a m p l i t u d e s p e c t r a over a narrow  interference  obtained  differential  i n a d e t a i l e d study  f r o m a s i n g l e s t a t i o n were u n r e l i a b l e and could  length  results.  (1966), 1964  rupture  waves R2,R3, r e c o r d e d  1978)  16,  waves u n d e r g o i n g r e f r a c t i o n s due crust,  function  Pasadena  because A k i  t h e N i i g a t a e a r t h q u a k e of J u n e variability  the  Rayleigh  t o s u p p l e m e n t Ben-Menahem's ( 1 9 6 7 , This  of  define  the the  two  oblique  largest  aftershocks  subduction  used to o b t a i n the a z i m u t h a l  process.  surface  as a f u n c t i o n of e a r t h q u a k e mechanism.  radiation  patterns  were  then  compared  wave These  to  the  18  observed r a d i a t i o n pattern u n t i l determined.  a  'best  f i t ' mechanism  was  19  II.  AFTERSHOCK ZONE OF Analysis  a new  1949  determination  records. arrival  The  of  SIT  aftershock  was  1949  the  aftershock  records The  estimated  zone  location  and  used  and to  a  traveltime  table  the  km/s,  z o n e began  phase  of a  each  revised  explosions al.,  standard a = 8.2  h=36  km,  and  produced  from  this  phase a r r i v a l  phase  simple  records  arrival model.  precludes  the  arrival  simpler  Assuming  picks  the  t r a v e l t i m e t a b l e was phases should other  the  arrive.  phase  times The  the  standard  (Pn,Pg,Sn,Sg)  s e l e c t i n g t h e most p r o m i n e n t a r r i v a l phase.  on  used, A  only  slow  phase consulted The  slightly  to  to  determine  s e i s m o g r a m was  speed, measure between  selected. achieved  assigning to i t a  identification  a r r i v a l s occurred  the phase a r r i v a l s d i d not  and  were  was  by trial  correct  when  the  the other  t h e n c h e c k e d t o see i f  at the p r e d i c t e d t i m e s .  appear at the  of  (Forsyth  drum  ability  model was  more  mainland  t i m e a c c u r a t e l y enough t o d i s t i n g u i s h  Therefore,  Phase  model.  a=.25.  i n B i r d L a k e i n t h e Queen C h a r l o t t e I s l a n d s  15mm/min, o f t h e SIT  models.  construction  E a r t h P h y s i c s B r a n c h m o d e l was  km/s,  2  1974)  different  with  using a l a y e r over a h a l f s p a c e  s o p h i s t i c a t e d model d e r i v e d from r e c o r d i n g s  the  SIT  PROCEDURE  a.i=6.2  the  the  magnitude construct  with  zone.  Specifically,  et  using  were e x a m i n e d f o r e v e n t s and  E v a l u a t i o n of the a f t e r s h o c k of  QUEEN CHARLOTTE EARTHQUAKE  Queen C h a r l o t t e e a r t h q u a k e began  p i c k s were made.  earthquake  2.1  of the  THE  correct  times  a  If new  20  phase  identification  o f t h e most p r o m i n e n t  the procedure repeated u n t i l arrival  times  After  arrival  the predicted  and  was made a n d  observed  phase  coincided. the  phases  were  identified  determined from t h e t r a v e l t i m e t a b l e ,  and  the  distance  the l o c a l magnitude  e s t i m a t e d f r o m t h e l o g o f t h e maximum t r a c e  amplitude  M  was  and t h e  l o g of t h e d i s t a n c e t o t h e earthquake.  M.=log(a)+31ogA-2.92+0 Where a i s t h e maximum g r o u n d a m p l i t u d e i n *xm, A i s i n km, a n d /3 i s a s t a t i o n c o r r e c t i o n ( K a s a h a r a , 1 9 8 1 ) .  The  maximum  trace  amplitude  was  used  i n s t e a d of t h e ground  displacement, with the constant m u l t i p l i c a t i v e c o r r e c t i o n to convert the t r a c e amplitude t o the true obsorbed The  into  the  e m p i r i c a l l y determined s t a t i o n  station correction  correction  which  ground  was  determined  b r o u g h t my m a g n i t u d e  by  trying  displacement correction. to  estimates into  w i t h Rogers'  (1983) e s t i m a t e s f o r t h e 12 e a r t h q u a k e s we  common.  A  standard  magnitude  e s t i m a t e s , b a s e d on t h e V I C r e c o r d s , a r e  the  deviation  find  a  agreement had i n  o f a=0.4 i s f o u n d when R o g e r s ' compared  to  s t a t i o n c o r r e c t e d S I T e s t i m a t e s ( s e e T a b l e I I f o r a summary  of t h e a f t e r s h o c k After  the  information). distance  of  the  earthquake  from  d e t e r m i n e d , t h e e a r t h q u a k e was a r c e d a t t h e a p p r o p r i a t e a c r o s s t h e Queen C h a r l o t t e f a u l t that  needed  i t occurred  justification  on  the  for locating  SIT  was  distance  and p l o t t e d w i t h t h e assumption  fault  ( s e e F i g u r e 9 ) . The p r i m a r y  the epicenters along the fault  comes  21  from the in  observations  t h e Queen C h a r l o t t e  Charlotte of  t h a t almost a l l the  the  Rogers  fault eight  (see  Figure  largest  (1983),  aftershocks  to  R o g e r s ' l o c a t i o n , two and  arrivals  (ISS)  Bulletin  Rogers' the  SIT  origin  epicenter  as  located  further  agreed  perfectly.  by  l o c a t i o n s are km)  five  Rogers'  as  no he  more a c c u r a t e lacked of  ^50  time (±25  four  km  from  and  ten  epicenter the  Center  tables. km)  than  good c o n t r o l of km  in  by  the  epicenter  c o m b i n e d u n c e r t a i n t i e s of b o t h methods  arcing  is a valid  50  International Seismological  disagreements  Charlotte Fault  found  a computer program which u t i l i z e d  i n the  w i t h i n the  locations  much as  J e f f r e y s - B u l l e n (1967) t r a v e l  Thus,  that  south  Queen  well located  north  by  the  the  further  time.  indicate  considered  seismicity on  locations  (±25  are  occurred  A c o m p a r i s o n of  determinations  locations and  and  has  epicenter  two  reported  5).  SIT  l o c a t i o n s were made u s i n g P  region  aftershocks,  the  located  kilometers,  Islands  historical  the  epicenters  procedure.  across  the  Queen  22  SITKA ARRIVAL TIME  DATE  SITKA S-P  IMPLIED SITKA DELTA  ROGERS DELTA  SITKA MAX. AMP./PER.  325KM 387SG-PG 375KM 527SG-PN 100KM 127SG-PG 125KM 167SG-PG 400KM 587SG-PN TOO SMALL TO P I C K  SITKA CODA DURATION  SITKA MAGNITUDE ESTIMATE 4 .47 4 .4?  8/22 8/22 8/22 8/22 8/22 8/22 8/22 8/22 8/22 8/22 8/22 8/22 8/22 8/22 8/22 8/22 8/22 8/22 8/22  05 06 06 06 07 07 07 07 08 08 09 09 12 12 13 15 17 19 21  53 07 16 50 02 21 44 50 14 18 08 15 05 2 1 40 27 55 46 41  OO 05 29 07 Ol 55 09 23 31 40 35 15 02 21 25 15 20 18 46  30 SG-PG 20 SG-PG 68 S G - P G 40 SG-PG 40 SG-PN 20 SG-PG 15 S G - P G 27 S G - P N 20 SG-PG 6 SG-PN 20 SG-PG 207SG-PG  8/23 8/23 8/23 8/23 8/23 8/23 8/23 8/23  OO Ol 02 14 19 19 20 23  37 00 59 15 38 44 25 42  48 09 43 34 45 46 44 44  38 S G - P G 427SG-PN 397SG-PN 28 S N - P N 707SG-PG 547SN-PN 50 SN-PN 22 S G - P G  8/24 8/24 8/24 8/24 8/24  02 09 12 21 22  39 21 42 52 38  35 02 48 14 24  7 SEC TOO EMERGENT TO GUESS 2.5MM/4SEC 4 5 0 SEC 4 8 4 50KM 46 S N - P N 4MM/4SEC 2GO S E C 200KM 4 .. 1 23 S G - P G 10MM/2SEC 180 S E C 300KM 4 . 4 40 SG-PN 5MM/2SEC 200 SEC 525KM 520KM 75 SG-PN 6 0 0 SEC 10MM/4SEC 5..4  8/25  15 25 28  8/26 8/26  OS 26 22 4 0  14 19  8/27  21  48  9/02 9/02 9/02 9/05  06  55  9/ 1 1  23  29 04  9/12 9/12  0 8 36 14 38  48 31  307SN-PN 307SN-PN  275KM 260KM- P 275KM 2 8 5 K M - P  9/18 9/18  07 53 54 1 1 59 44  447SG-PN 39 S N - P N  325KM 370KM  SG-PN  120 135 420 60 140 100 48 220 56 240 160 270 90 480 345 90 120 250 120  SEC SEC SEC SEC SEC SEC SEC SEC SEC SEC SEC SEC SEC SEC SEC SEC SEC SEC SEC  320KM 300KM 300KM 275KM 6CKDKM 550KM 500KM 200KM  1.5MM/2SEC 2MM/2SEC 250KM--P 47MM/1SEC 7MM/4SEC 590KM 4MM/4SEC ' 570KM UNREADABLE 545KM 5MM/2SEC  75 120 GOO 220  SEC SEC SEC SEC  105 S E C  407SG-PN 20 PG-PN  300KM 120KM-•P 65MM/4SEC 275KM 300KM 18MM/4SEC  23 M I N . 20 MIN.  44  SN-PN  425KM 475KM  6MM/4SEC  01 32 0 6 0 5 49 21 0 7 59 52  36 S N - P N 36 S G - P N 327SG-PN  350KM 350KM 275KM 250KM  io  427SN-PN 42  SG-PN  Table  200KM  120 SEC  4MM/1SEC  31  24  250KM 175KM SOOKM 340KM 300KM 175KM 125KM 225KM 175KM 125KM 175KM 170KM  4MM/2SEC 3MM/2SEC 65MM? 2MM7 1 MM/2SEC 1MM7 <.57 4MM/2SEC . 5MM/1SEC 4MM/2SEC 2MM/4SEC 270KM -P 12MM/1 SEC 2MM/3SEC 41.5MM/2SEC 12.5MM/1SEC 3MM/2SEC 3MM/1 SEC 10MM/2SEC 2.5MM/1 S E C  ROGERS MAGNITUDE  3 . 77 2.8? 4 .07  4  .0 3 .5 4 .0  4. 1 4. 7  4  3 .3 4 .2  .5  4 .4 3 .4 3 .O 4 .O 3 . 37 3 .9 4 .07 5 . 37 4 .4 5 .2  .  5 .0 5 .O 5 .0 6.4  3. 8  3.  4  .9  7  5 . 57 4.8  4 .9 5. O  720 SEC  4 .9  5. 3  5MM/1 SEC 3.5MM/2SEC 2MM/2SEC  2 4 0 SEC 180 SEC 45 S E C  4 .6 4. 1  4 .6  400KM 425KM- P  9MM/4SEC  300 SEC  5 . O?  225KM  3MM/4SEC  240 SEC  3. 8  6MM/4SEC 22MM/2SEC  240 SEC 330 SEC  4 . 37 4 . 97  2MM/4SEC 3MM/2SEC  120 SEC 120 SEC  4 .07 4 .4  I I - AFTERSHOCK  3. 77  DATA  This t a b l e summarizes the a f t e r s h o c k data SIT. The ? i n d i c a t e s the adjacent value is uncertain.  recorded at or reading  4 .9  4 .9 5. 0  23  Figure  9 - AFTERSHOCK  LOCATIONS  The solid dots i n d i c a t e the p o s i t i o n of a f t e r s h o c k s i d e n t i f i e d on t h e S I T r e c o r d s when p l o t t e d on t h e Queen C h a r l o t t e Fault. The l a t e r a l d i s t r i b u t i o n of epicenters arranged perpendicular to the fault i n d i c a t e s t h a t more t h a n one e a r t h q u a k e was l o c a t e d a t the given p o s i t i o n on t h e f a u l t . The primary j u s t i f i c a t i o n f o r l o c a t i n g the epicenters along the fault i s the observation that almost a l l h i s t o r i c a l s e i s m i c i t y i n t h e Queen C h a r l o t t e I s l a n d s region has o c c u r r e d a l o n g t h e Queen C h a r l o t t e f a u l t .  24  An  attempt  was made t o c o n s t r a i n t h e n o r t h - s o u t h  of t h e l a r g e r e v e n t s slightly  more  n o r t h or south  SIT i n t o agreement. larger  closely  procedure,  proved  seismograms  epicenter  prevented  applied  epicenters  times  a t VIC and  to  obtained,  any  six  In  but  matching  the SIT r e c o r d s  h o r i z o n t a l components.  the cases  nature  of  improvement  in  difficult.  The  VIC r e c o r d s  have a low n o i s e  that  could  be  makes  accurate  c o n s i s t of a s h o r t p e r i o d  w h i c h i s c o n t a m i n a t e d by c o n s i d e r a b l e times  determined  noise.  due  to  the  times  period  vertical accurate  f a s t drum s p e e d However,  the  f o r t h e M=8.1, M=6.2, a n d M=6.4 e v e n t s  do n o t a g r e e w i t h t h e t i m e s  reported  makes  times  absolute  and  timing  For VIC,  (60mm/min) i f t h e a r r i v a l s o f S a n d P a r e c l e a r . P arrival  level  They a r e , h o w e v e r , l o n g  w i t h a s l o w drum s p e e d (I5mm/min)  measured  most  the  significant  of  location.  In p a r t i c u l a r ,  S-P  the  inconclusive.  a g r e e m e n t b e t w e e n V I C and S I T was the  moving  to b r i n g the P a r r i v a l  This  aftershocks,  by  position  arrival  i n t h e ISS B u l l e t i n ,  suspect.  Thus,  c o m p a r i n g P a r r i v a l s a t V I C and S I T , I e n d e d  up  which  instead  comparing  of S-P  times. The  level  of  noise, along  w i t h t h e emergent c h a r a c t e r  t h e p h a s e a r r i v a l s a t V I C , meant t h a t t h e were  often  uncertain  by  several  phase  seconds.  apparent phase a r r i v a l  times  arrival  on t h e S I T e p i c e n t e r  times  based  the  epicenter  In  were c o n s i s t e n t w i t h  the u n c e r t a i n t y i n the p r e c i s e VIC that  arrival  phase  l o c a t i o n could vary  of  picks  g e n e r a l , the the  expected  locations.  However,  arrival  times  means  by a s much a s 20 km and  25  still  appear  to s a t i s f y  Generally, main f a c t o r best,  an  which  however, the  in limiting arrival  at  phase a r r i v a l  t h e SIT phase a r r i v a l s  the assumption  Fault  is valid,  SIT  mm,  c a n be  identified  i n a r r i v a l time  in epicenter distance. c a n be m e a s u r e d  that the earthquakes  or  (see  F i g u r e 10).  A l t h o u g h t h e Chatham  time  Chatham  active.  no m i c r o e a r t h q u a k e  SIT  Horner,  for  the  M=8.1  r e l a t e d t o t h e M=8.1 Charlotte  Fault  Few,  the  however, of given  i s more t y p i c a l .  Thus,  might  faults  instead  was  Strait  1983).  There  is  earthquakes  and  the  fault  moved  t h e r e i s no have  occurred  t i m e s , and t h e r e field  no  direct  on  the  event, event,  onset  of  events  as  such,  lie  not the F a i r w e a t h e r F a u l t .  was  study  evidence  Fairweather i n the M=8.1  immediately  suggests that the earthquakes and  in  evidence  absence of s e i s m i c a c t i v i t y  sudden  on  also considered  earthquakes  in historic  l i e  s e v e r a l months i m m e d i a t e l y p r e c e d i n g t h e  event, coupled w i t h following  s corresponding  a c t i v i t y a l o n g i t d u r i n g a 1969  However, t h e c o m p l e t e  region  major  fault  a g a i n s t the o c c u r r e n c e of the Fault.  s.  accuracy  Page,1969),  No  Chatham S t r a i t  (Rogers,1976;  Strait  (Lathram,1964;  i t is still the  0.8  km.  Fairweather  near  to km  the  that  i s 1.6  of  then e p i c e n t e r l o c a t i o n s u s i n g SIT a r e p r o b a b l y  possiblity  Cenozoic  t o w i t h i n 0.2  t h a t t h e e p i c e n t e r s l i e on t h e Queen C h a r l o t t e  u n c e r t a i n t o ±25 The  i s the At  a b o v e ; i n s t e a d , an u n c e r t a i n t y o f ±25 if  of SIT  the a c c u r a c y of e p i c e n t e r l o c a t i o n .  t i m e , the combined u n c e r t a i n t y  a 15 km u n c e r t a i n t y  times.  15 mm/min drum s p e e d  t r a n s l a t e s t o an u n c e r t a i n t y  F o r an S-P to  t h e VIC  are  on  the  Queen  The  successful  26  c r o s s - c h e c k w i t h VIC of s i x of t h e earthquakes a l s o all  the earthquakes  I50°W 64°  l i e on t h e Queen C h a r l o t t e  14 0  a  implies  fault.  130°  62  60  58°  56°  F i g u r e 10 - RELATIONSHIP OF THE CHATHAM S T R A I T AND FAIRWEATHER FAULTS TO THE QUEEN CHARLOTTE FAULT The location o f S I T i s shown r e l a t i v e t o t h e C h a t h a m Strait fault and the Fairweather fault. The earthquakes a r e a s s u m e d t o h a v e o c c u r r e d on t h e Queen C h a r l o t t e f a u l t a s the Chatham S t r a i t f a u l t shows no evidence of still being active, and t h e time c o r r e l a t i o n b e t w e e n t h e M=8.1 event and the other earthquakes suggests that the earthquakes are a f t e r s h o c k s o f t h e M=8.1 e v e n t , a n d , a s s u c h , l i e on the Queen Charlotte fault and not t h e F a i r w e a t h e r f a u l t ( a d a p t e d from Perez and Jacob, 1980).  that  27  2.2  RESULTS A time  h i s t o r y of the a f t e r s h o c k s  The e m p i r i c a l  rule  O m o r i , and g i v e n  for aftershock  i n Richter  i s shown i n  frequency  first  Figure  11.  p o i n t e d o u t by  (1958), i s , A=N(1+kt)  A=Number o f a f t e r s h o c k s i n a s p e c i f i e d interval. k,N=Constants chosen t o f i t the d a t a .  The  aftershocks  do  s t a t i s t i c s a r e poor  appear t o f o l l o w due  to  the  time  Omori's law, a l t h o u g h the  small  number  of  measurable  earthquakes.  Figure  range  11 - TIME DISTRIBUTION OF AFTERSHOCKS  This plot shows t h e number of e a r t h q u a k e s o c c u r r e d on s u c c e s s i v e d a y s f o l l o w i n g t h e M=8.1  which event.  During  earthquakes  in  the f i r s t location  s i x days of from  300  km  aftershocks to  the  the  north  o f t h e M=8.1  • 28  epicenter 490  t o 190 km t o t h e s o u t h ,  primarily  length, Acharya  aftershock  (1979) d e r i v e d  magnitude-rupture area  parts  of  the world  each  region,  but  significant. variations  It are  is  due  to  clear  the type  region  relationships  •. i s  None  of  the  applicability  Queen  relationships usefulness. Acharya  much  For  i s high  for  of  the  regional  o f p l a t e i n t e r a c t i o n , a n d how  f o r the  different strike-slip  f o r which  relationships  Andean  from  his  region  and  match  Acharya the  nature  found and  C h a r l o t t e F a u l t Zone, a n d , t h e r e f o r e , t h e  by  t o t h e Queen C h a r l o t t e  regional  other  instance,  (1979) p r e d i c t s a  Charlotte  how  regions  Likewise  derived  different  region to region are  relationship  of h i s r e l a t i o n s h i p s  questionable.  length  (see Figure 12).  seven  magnitude-rupture length of  from  significantly  region  the  f o r seven  magnitude  f o r b o t h t h e San A n d r e a s  the Japan s u b d u c t i o n  the rupture  of the l i t h o s p h e r e of the i n t e r a c t i n g  For instance, Acharya's  subduction  style  l e n g t h and  not  define  12 a n d 1 3 ) . He f o u n d t h a t t h e  variations  much a r e due t o t h e n a t u r e plates.  to  r e g i o n a l magnitude-rupture  (see Figures  that  data  relationships  c o r r e l a t i o n between r u p t u r e  is  zone o f  km ( s e e F i g u r e 9 ) . Using  and  y i e l d i n g an a f t e r s h o c k  the  authors  or  worldwide-averaged  are  w e s t e r n U.S.  rupture-length  fault  of  uncertain  r e l a t i o n s h i p of  f o r the  1949  Queen  I s l a n d s e a r t h q u a k e o f 301 km, b u t t h e A l a s k a - A l e u t i a n  r e l a t i o n s h i p p r e d i c t s a r u p t u r e - l e n g t h o f 494 km.  29  MAGNITUDE  Figure  12 - EMPIRICAL MAGNITUDE RUPTURE-LENGTH RELATIONSHIP FOR 7 REGIONS OF THE WORLD  T h i s f i g u r e shows t h e l a r g e v a r i a b i l i t y i n magnitude rupture-length r e l a t i o n s h i p s o b t a i n e d by A c h a r y a f o r d i f f e r e n t r e g i o n s of t h e world (from Acharya, 1979). Wyss produce  (1978) has s u g g e s t e d less  powerful  earthquakes  earthquake magnitude should area. A=fault  t h a t s i n c e long but than  be e s t i m a t e d  The r e l a t i o n s h i p s u g g e s t e d  by  thin  faults  l o n g and wide  faults,  on t h e b a s i s o f r u p t u r e  Wyss,  Ms=logA+4.2  area, c o n s i s t e n t l y p r e d i c t s a smaller rupture area  where than  30  Acharya's region suggest  magnitude-rupture  (see F i g u r e a minimum  0*|  13).  area r e l a t i o n s h i p  Thus,  Wyss'  rupture area  f o r any  individual  r e l a t i o n s h i p c a n be u s e d t o  f o r a given  earthquake.  —  /  P  ///  ' W / f  / / .  '  ////  /  V  ////*/  /  / '  /  4  / /  ////  / ///,// MAGNITUOE  Figure  13 - MAGNITUDE RUPTURE-AREA  RELATIONSHIPS  T h i s f i g u r e shows t h e v a r i a b i l i t y of the magnitude r u p t u r e - a r e a r e l a t i o n s h i p s d e r i v e d by A c h a r y a f o r f i v e different r e g i o n s of the world. Note that the r e l a t i o n s h i p o f Wyss (1978) c a n be used as a lower l i m i t f o r a l l regions (from Acharya, 1 9 7 9 ) .  31  For  the  1949  Queen  Charlotte  relationship predicts a rupture  area  I s l a n d s e a r t h q u a k e , Wyss' of  7943  km .  If  2  this  r u p t u r e a r e a i s d i v i d e d by 16 km, t h e d e p t h t o w h i c h Hyndman a n d Ellis the  (1981)  submarine  have s u g g e s t e d t h a t b r i t t l e terrace  Queen C h a r l o t t e km.  ( t h e oceanward s i d e of t h e presumed  fault),  observed  Charlotte Fault rupture  length  suggest  a  agreement  depth  of  is  minimum  selection  in  of  he  worldwide  fits data,  o f 557 km i s d e r i v e d  earthquakes  along  t h e Queen  the  predicted  then  they  a  Wyss  least  in  the  this  reasonable  ( 1 9 7 9 ) , i n a more  squares  suggests With  are  line  second Figure and the  to  constant  change,  a  i n the rupture  km.  and time development  occurring  trend in  of the a f t e r s h o c k s are  i s observed. the  34  Twenty-two of  hours  immediately the  M=8.1  w h i l e f i v e of e i g h t earthquakes t h a t o c c u r r e d i n the  34 h o u r s a r e l o c a t e d t o t h e s o u t h o f t h e main s h o c k 14).  (see  T h e s e a f t e r s h o c k s a r e c a u s e d by t h e s l o w r e w o r k i n g  readjustment of the s t r a i n rapid  a  f o r a f a u l t w i d t h o f 16 km, a n d 424  f o l l o w i n g t h e main shock a r e l o c a t e d t o t h e n o r t h of epicenter,  the  length,  examined i n d e t a i l , a d i s t i n c t 23  km,  rupture  km f o r a f a u l t w i d t h o f 21  the  1981),  21  B e a r i n g i n m i n d t h a t t h e s e numbers  which  the s p a t i a l  be  378 km.  f o r m u l a s h o u l d be 4.15 n o t 4.2.  If  to  microearthquakes  w i t h t h e SIT a f t e r s h o c k zone.  r e c e n t paper  length  assumed  (Hyndman a n d E l l i s , is  active  t h e n t h e p r e d i c t e d r u p t u r e l e n g t h i s 496  I f t h e w i d t h of t h e f a u l t  maximum  f r a c t u r e can occur i n  change  in  stress  along the f a u l t  in  response  to  a n d s t r a i n o f t h e main r u p t u r e .  A p p a r e n t l y t h e r e w o r k i n g o c c u r r e d more r a p i d l y  to the  north  of  32  the main shock e p i c e n t e r  than to the  also  occurred  appears  to  events to the The  have  n o r t h than to the  October end  previous  aftershocks  months.  Therefore,  o f t h e M=8.1  occurring during to  at  the  event,  end  of  the the  s h o c k and  M=8.1  t o be  records,  following  i t ,  though  by  Kelleher's  earthquake  sequence  zone,  event.  and  However,  of  the  z o n e of t h e A u g u s t 21  38  which when  had  identified not  plotted  the  not  it  is  October  August  21  earthquake  i m p l i e s t h a t a s u g g e s t e d s e i s m i c gap  August  22  earthquake  does  suggests  not a  of the main shock  km.  the been  the  Queen  This  fault  t o the n o r t h of The  variation  sequence, w i t h the a f t e r s h o c k s c l u s t e r i n g south  along  exist.  time  from  previously  l e n g t h o f 490  length  then to the  1-1/2 events  rupture  e a r t h q u a k e s were  earthquakes,  also  for  three  aftershocks  Charlotte Fault indicate a rupture  distribution  from  size.  including  The  the  the  distinct  M=8.1  overall aftershock  change i n  recognized.  and  separated  c o u l d be c o n s i d e r e d  t o be a s e p a r a t e ,  I n summary, o v e r 50 SIT  is  t o n o t e t h a t r e g a r d l e s s of whether or not  the  does not  zone,  34 h o u r s i m m e d i a t e l y  events are considered  event,,  south.  O c t o b e r 31  n e c c e s a r i l y a f t e r s h o c k s of  31  w i t h s m a l l e r but more numerous  aftershock  the  M=8.1  northern  important  readjustment  by an a b s e n c e o f s e i s m i c a c t i v i t y  the  the  (1972) c r i t e r i a  The  31, M=6.2 e a r t h q u a k e , t h o u g h l o c a t e d w i t h i n  northern  related  south.  first  aftershock  i n the to  epicenter.  the  the  rupture north,  FIRST 34 HOURS  S E C O N D 34 HOURS  Figure  14 - TIME PROGRESSION OF  O C T . 31 S E Q U E N C E  AFTERSHOCKS  D u r i n g t h e f i r s t 34 h o u r s a f t e r t h e M=8.1 e v e n t , 22 o f 23 earthquakes o c c u r r e d t o t h e n o r t h o f t h e M=8.1 epicenter. During the second 34 h o u r s , 5 of 8 earthquakes occurred to the south o f t h e M=8.1 epicenter. The O c t o b e r 31 sequence i s w i t h i n the a f t e r s h o c k z o n e , t h o u g h a t t h e v e r y n o t h e r n end of i t , and separated i n t i m e f r o m t h e o t h e r e a r t h q u a k e s by o v e r a month o f s e i s m i c i n a c t i v i t y .  34  III. 3.1  SURFACE WAVE ANALYSIS  POINT SOURCE MECHANISM SOLUTION  3.1.1  Introduction The  azimuthal radiation  waves i s s e n s i t i v e  p a t t e r n o f L o v e waves a n d R a y l e i g h  t o t h e e a r t h q u a k e mechanism a n d f o c a l  depth.  For  t h o s e e a r t h q u a k e s w h i c h c a n be r e p r e s e n t e d by a p o i n t  the  theoretical  in  a  s u r f a c e wave r a d i a t i o n  straightforward  s u r f a c e wave r a d i a t i o n the  manner.  By  p a t t e r n c a n be c a l c u l a t e d comparing  the  radiation  i s found  f o r which  the calculated  p a t t e r n matches t h e o b s e r v e d  one.  pattern  T h i s i s done  by t r y i n g many d i f f e r e n t e a r t h q u a k e m e c h a n i s m s u n t i l depth  calculated  pattern t o t h e observed r a d i a t i o n  e a r t h q u a k e m e c h a n i s m a n d d e p t h c a n be d e d u c e d .  and  source  a mechanism s u r f a c e wave  For  earthquakes  whose s p a t i a l d i m e n s i o n s a r e s m a l l c o m p a r e d t o t h e w a v e l e n g t h o f the.  surface  c a n be  used.  relationship Queen  waves b e i n g a n a l y z e d , a p o i n t s o u r c e a p p r o x i m a t i o n Applying  Wyss'  (1978)  magnitude-rupture  t o a M=6.4 e a r t h q u a k e a n d d i v i d i n g  Charlotte  fault,  theresulting  fault  by 16 km f o r t h e  length  i s 9.9 km.  T h u s , i f s u r f a c e Waves o f p e r i o d >20 s a r e a n a l y s e d , source used  approximation  i s valid  (Tsai  a n d A k i , 1970)  the  point  a n d c a n be  f o r t h e A u g u s t 23 M=6.4 e a r t h q u a k e a n d t h e O c t o b e r  earthquake.  area  31 M=6\2  35  3.1.2  T h e o r y And The  computer programs used  were d e v e l o p e d follow  Computer P r o g r a m s  by Herrmann  Harkrider  t o e v a l u a t e the source  (1978).  (1970)  in  These  their  programs  method  differential  e q u a t i o n s w h i c h a r i s e when t r y i n g  theoretical  surface  station  a r b i t r a r y , azimuth  of  earthquake The The  wave  amplitude and  essentially  of to  spectrum  mechanism  solving  the  evaluate  the  recorded  distance  at  a  from  a  given  e q u a t i o n t o be s o l v e d i s Newton's s e c o n d  law  applied  in a layered earth.  t h e o r y i s o u t l i n e d as  basic  w i t h i n an e l a s t i c  follows:  body, pU=f  ;  +r  (1)  ;j  where, p i s the d e n s i t y U i s t h e i t h component o f g r o u n d a c c e l e r a t i o n f i s t h e i - t h component of t h e a p p l i e d body f o r c e s t i s t h e i - t h component o f t r a c t i o n a c r o s s t h e p l a n e w i t h a normal t o the j - t h a x i s . R a y l e i g h wave s o l u t i o n s a r e s o u g h t  of the  form,  U=r , ( k , z ,w)exp( i ( kx-cot) ) V=0 W=ir (k,z,w)exp(i(kx-wt)) 2  With, U=total V=total W=total k=wave  displacement displacement displacement number  i n the x i n the y i n the z  direction direction direction  36  w=frequency r, (k,z,cj)=horizontal displacement r ( k, z ,a>) = v e r t i c a l d i s p l a c e m e n t 2  This  corresponds,  prograde i.  motion  for  i n t h e x-z p l a n e .  Traction=0  ii.  positive  real  v a l u e s of r , and r  2  , to  The b o u n d a r y c o n d i t i o n s a r e ,  at the free surface  (z=0).  No s o u r c e e x i s t s a t z=°°.  iii. T r a c t i o n and d i s p l a c e m e n t must be continuous across interfaces where medium properties have discontinuities.  With  these boundary c o n d i t i o n s  layer  i s homogeneous  and  and i s o t r o p i c ,  r =ir a j  f l  the  assumption  (k,z,o>)exp( i k x - c o t ) )  2  7^, = i ( X ( d r / d z ) + k X r , ) e x p ( i ( k x - w t ) ) 2  t  =ir (k,z,u)exp(i(kx-wt)) 3  with r (k , z ,CJ) = s h e a r ( o r h o r i z o n t a l ) s t r e s s rn(k,z,w)=normal (or v e r t i c a l ) s t r e s s X a n d n=Latae constants. 3  each  t h e s t r e s s c o m p o n e n t s become  r = i ( X ( d r /dz)+kX+2/ir , )exp( i ( k x - u t ) ) trt  that  37  Substitution  of  differential  equations  (ri,r ,r ,r,) 2  (2) and  3  (3) for  into  ( l ) provides  the  a  s e t of  stress-motion  w h i c h c a n be w r i t t e n i n m a t r i x o  vector  form a s ,  o  • AW *)  6  (Mt)*2/*(t)]  GO  O  o  The  boundary  conditions  of  vanishing  traction  at  the free  s u r f a c e z = 0 a n d no m o t i o n a t z=<*> i.e.  r , , r  r ,r„  2  * 0 as z  •O a s z = z = 0  3  o  mean t h a t f o r a g i v e n a n o n v a n i s h i n g certain  K=Kn(cj)  ( A k i and  Cn=cj/Kn(cj) i s a l s o This  i s an  computer  Richards,  is  formulation  assumed  given  (Haskell,  the  vector  Repeated a p p l i c a t i o n  for  velocity  The  f o r which the eigenvalues To f i n d  the s o l u t i o n  first  1953) i s u s e d .  matrix  operator  can  method i t within a  derived  which  v e c t o r a t one s i d e o f an e l a s t i c  at  the  other  this  Thompson-Haskell  In t h i s  be  o r phase to  t h a t t h e medium p a r a m e t e r s r e m a i n c o n s t a n t  the stress-motion to  Phase  problem.  i n a m u l t i l a y e r e d medium, a  l a y e r so t h a t a  relates layer  problem  only  SURFACE, t a k e s a s i n p u t an e a r t h model a n d a  v e l o c i t i e s a r e t o be d e t e r m i n e d .  matrix  1980).  exist  discretized.  range of f r e q u e n c i e s  eigenvalue  solutions  eigenvalue-eigenfunction  program,  selected  •*=>  s i d e o f t h e same  o f t h i s method a l l o w s one t o s t a r t  solid  layer. at the  38  halfspace  at  the  bottom  and  work up  to the s u r f a c e l a y e r - b y -  layer . Briefly, matrix  the computation  transformations  matrix equation frequency  proceeds  to Equation  by a p p l y i n g a  is  solved  of  (4) t o o b t a i n a homogeneous  known a s t h e f r e q u e n c y  function  series  by  or p e r i o d f u n c t i o n .  seeking  the  zeros  The of  the  e q u a t i o n a s a f u n c t i o n of p h a s e v e l o c i t y , wave number,  and  elastic  initially  constants  specifying The  the  layers.  t h e wave number, Kn,  elements  each  of  a trial  phase v e l o c i t y ,  of t h e T h o m p s o n - H a s k e l l m a t r i x a r e t h e n  Cn.  formed  for  l a y e r and m u l t i p l i e d by t h e m a t r i x f o r t h e l a y e r a b o v e i t ,  s t a r t i n g w i t h the frequency product  values mode.  half  function  m a t r i x and  The  frequency  A new  trial  on  space.  is  calculated  halving  larger  v a l u e of Cn  is  the  detected.  procedure  sign  is  used  scheme  accuracy.  resulting  up  to  f u n c t i o n of d e p t h .  the  of the  feature  chosen of  (larger  final  that, i t s  or  the frequency of  and  then  e i g e n v a l u e , Cn,  equation i s  the  frequency  finally  the  A similiar  f o l l o w e d f o r Love waves.  interval  a  linear  to the r e q u i r e d  i s passed  to  a  numerically integrates Equations  find  lowest smaller  t h e r o o t i s b r a c k e t e d an  i s f o l l o w e d t o p r o d u c e Cn  p r o g r a m , REIGEN, w h i c h bottom  of  than the r o o t i n the  a change i n s i g n  After  interpolation The  value  elements  important  f o r Cn's  whether  is  numerical from  f u n c t i o n has.the  p o s i t i v e or n e g a t i v e ) u n t i l equation  The  stored.  are p o s i t i v e  depending  the  and  . T h i s i s done by  the  second (4)  from  e i g e n f u n c t i o n ( r , , r , r , r „) a s a 2  s e t o f e q u a t i o n s and  3  procedure  is  39  The  eigenvalues  dependent  but  not  and source  a p p r o p r i a t e e a r t h model and t h e r e s u l t i n g The and  selected  stored  Using  tape  point  and  for  the eigenvalues  have  transformed  equation  i s given  and t h e g r o u p v e l o c i t y ,  programs a r e r u n ,  a  the  eigenvalues  computes  the surface  point  source  at  a  and e i g e n f u n c t i o n s t h e functions,  can  be  f o r c e F(w)  1980),  i n t o a more a p p r o p r i a t e  cylindrical  by, p(r,+r )dz 2  U g , i s d e t e r m i n e d by d i f f e r e n t i a t i n g  The c o m p u t e r p r o g r a m however,  the  system.  1=1/2  forces;  on  i s ( A k i and R i c h a r d s ,  polar coordinate  in this  Once  The R a y l e i g h G r e e n ' s f u n c t i o n f o r a p o i n t  acting at  model  and e i g e n f u n c t i o n s a r e s t o r e d .  r e s p o n s e o f t h e medium, t h e G r e e n ' s  we  earth  dependent.  h a s been s e l e c t e d b o t h  a t an a r b i t r a r y  depth.  evaluated.  I  station  are  t h i r d c o m p u t e r p r o g r a m , WIGGLE, t a k e s  displacement  where  or  eigenvalues  eigenfunctions  impulse  eigenfunctions  for this  i s w r i t t e n i n terms of e q u i v a l e n t o u t l i n e the r e s u l t s  can  be  Cn. body  obtained  40  faster  by u s i n g t h e  Richards,  moment  tensor  formulation  ( s e e A k i and  1980).  where U = i - t h component o f r e c e i v e r d i s p l a c e m e n t X=the v e c t o r p o s i t i o n o f t h e r e c e i v e r M p q = e l e m e n t s o f t h e moment t e n s o r G i p = e l e m e n t s o f t h e G r e e n ' s f u n c t i o n ( i - t h component o f d i s p l a c e m e n t due t o a n i m p u l s e f o r c e i n t h e in' t h e p - t h d i r e c t i o n ) .  In  d i f f e r e n t i a t i n g the Green's f u n c t i o n only the l a r g e s t or f a r .  field  terms  are retained.  be c o m p u t e d f r o m  the earthquake  i n A k i and R i c h a r d s , The variation  program Love  earthquake. of  focal  several  and  f a u l t parameters  (eg.,  can Box  4.4  1980). QUESTION  accepts  Rayleigh  wave  the  observed  amplitude  azimuthal  spectra  f o r an  The p r o g r a m t h e n s e a r c h e s t h r o u g h a p a r a m e t e r  space  mechanism o r i e n t a t i o n s and f o c a l d e p t h s , and computes goodness-of-fit  determine which  The moment t e n s o r c o m p o n e n t s  the  the  the t o t a l i t y  are  observations.  These  coefficient  goodness  between t h e observed and  R a y l e i g h o r L o v e wave a m p l i t u d e s p e c t r a f o r o f d a t a from a l l azimuths  and p e r i o d s .  used  to  combination  include:  a) The c o r r e l a t i o n theoretical  which  b e s t f o c a l mechanism and f o c a l depth  satisfies  characteristics  characteristics  of f i t  41  b) S e i s m i c  moment e s t i m a t e  from Love waves.  c) S e i s m i c  moment e s t i m a t e  from R a y l e i g h  waves.  d ) Sum o f s q u a r e r e s i d u a l s b e t w e e n o b s e r v e d R a y l e i g h wave a m p l i t u d e  and t h e o r e t i c a l  s p e c t r a u s i n g t h e a v e r a g e s e i s m i c moment  est imate. e) S q u a r e r o o t o f t h e sum o f L o v e a n d R a y l e i g h wave s q u a r e  The  best  f o c a l mechanism e s t i m a t e  largest  correlation  i s usually the  coefficents  i n d e p e n d e n t s e i s m i c moment e s t i m a t e s Other  programs  from t h i s  are  available  and  one  with  f o r which  a r e as equal  as  residuals.  the  t h e two possible.  t o p l o t and d i s p l a y t h e r e s u l t s  program.  3.2 RUPTURE PARAMETERS 3.2.1 I n t r o d u c t i o n For longer by  l a r g e earthquakes the p o i n t source valid  of  an  extent  of  earthquake  the  doppler  the  asymmetry, can  effect the be  the  from a moving p o i n t s o u r c e . earthquake  derived.  rupture  Both  that  rupture  The  corresponds  length  and  length  f o r t h e M=8.1  asymmetery  l a r g e and e a s i l y  in  measured.  to  By a n a l y s i s o f rupture  and r u p t u r e  earthquake and  be d e r i v e d f o r t h i s e a r t h q u a k e a s i t i s s u f f i c i e n t l y the  finite  an a s y m m e t r y i n t o t h e  T h i s asymmetry  v e l o c i t y a r e parameters of i n t e r e s t can  earthquake.  introduce  s u r f a c e wave r a d i a t i o n p a t t e r n .  velocity  i s no  a s t h e s u r f a c e wave r a d i a t i o n p a t t e r n i s a f f e c t e d  the large s p a t i a l  dimensions  approximation  large  t h e s u r f a c e wave r a d i a t i o n p a t t e r n i s  42  Ben-Menahem the  far-field  propagation  (1961) was t h e f i r s t surface  along  a  wave  amplitude  fault.  f i e l d displacement caused  to d e s c r i b e the effect spectrum  He d i d t h i s  by a  moving  of  rupture  by e x a m i n i n g  the f a r -  horizontal  harmonic  time dependence i n a l a y e r e d e l a s t i c  vertical  strike-slip  propagates  along  the f a r - f i e l d  fault  a fault  vertical  of  on  vertical  dipole  with  halfspace.  For a  extent  of l e n g t h b w i t h v e l o c i t y  d,  which  v , he f o u n d  R a y l e i g h wave d i s p l a c e m e n t U t o be  given  by, U(o)) = ( s i n ( 2 e ) / y r ) ( g ( c j ) k ( s i n ( X ) / X ) e x p { i (^+3TT/4) } where X= (irb/X) ( c / v - c o s f i )  (5J  >=w(t-r/c)-X  a n d where c i s t h e R a y l e i g h wave p h a s e v e l o c i t y , r t h e epicentral distance, 8 the azimuth to the station measured c o u n t e r c l o c k w i s e from t h e s t r i k e of t h e f a u l t a n d k t h e wave number o f s h e a r waves. g(w) i s a function which d e p e n d s on t h e s o u r c e t i m e f u n c t i o n , t h e w i d t h of t h e f a u l t , depth and f r e q u e n c y . For our purposes, useful  of  this  expression  are  f o r e x a m i n a t i o n o f t h e 1949 e a r t h q u a k e .  3.2.2 D i r e c t i v i t y The t e r m X.  two c o m p o n e n t s  effect  F u n c t i o n Theory of  The e f f e c t  amplitude spectrum  the of  f i n i t e dimensions  the  finiteness  of  i s e x p r e s s e d by t h e f a c t o r  n o d e s a t X=7r, 2ir, 3TT, . . .  i s contained i n the the  fault  on  the  s i n ( X ) / X which has  43  To  isolate  (1961)  t h e e f f e c t of t h e f i n i t e dimensions,  defined  the  spectral amplitudes  directivity  l e a v i n g the source a t  l e a v i n g the source with azimuth directivity  function  Ben-Menahem  as the r a t i o of the azimuth  0  to  those  9+ir.  | U ( u ) [ 0 ) 3 | / |U(o>)[0 +TT] |  function=  (c/v+cos0)sin{(wb/2c)(c/v-cos0)} ( c / v - c o s 0 ) s i n { (a)b/2c) ( c / v + c o s 0 ) j For a pure  strike-slip  angle, source time space  model.  undefined. error  function  a  pure  dip-slip  When o n l y one s t a t i o n  curves u n t i l a  fits  this  is  is  used  to  combination  found  which  the observed  curve.  fault  generate  of  The f i r s t  rupture  produces  ext.remum. w i l l X=(irb/\)  this  i s available,  of d i p  a  velocity  squares  o c c u r when  half  function i s  theoretical  a directivity  W i t h more t h a n one s t a t i o n , a l e a s t be u s e d .  i s independent  f u n c t i o n , or t h e l a y e r i n g of t h e e l a s t i c  For  approach  length  fault  trial  and  directivity and  rupture  curve t h a t best  technique  can  K=n.  (C/V-COS0)=TT  T h i s c a n be r e w r i t t e n a s X/c=(b/c)(c/v-cos0)=T(max) which will  corresponds occur.  to  the  maximum p e r i o d a t w h i c h an extremum  T h i s c a n a g a i n be r e w r i t t e n a s , b=T(max)c/(c/v-cos0)=T(max)/(1/v-cos0/c)  If  the f o l l o w i n g  s u b s t i t u t i o n s a r e made, x = T ( m a x ) , y = c o s 0 / c , a=b, B = 1 / V  then, a=x/(B-y) or,  44  y = - ( l / a ) x + B = Ax+B Each  s t a t i o n c a n be p l o t t e d  A=-l/a=-l/b.  a s a p o i n t w i t h an x v a l u e e q u a l t o  t h e maximum p e r i o d a t w h i c h an extremum o c c u r s , a n d t h e y equal  t o cos0/c.  A least  determined  with  the  l e n g t h , and t h e r e c i p r o c a l  rupture  the rupture Thus,  the  squares l i n e  to  use  this  function  r a t i o o f R2 a n d R3.  of t h e s l o p e  yielding  of t h e y - i n t e r c e p t  function  a least  squares  line  points.  The  negative  squares l i n e w i l l  taking  giving  observed  the s p e c t r a l  amplitude  f o r a given point occurs  The x v a l u e  in  the  A point i s plotted drawn  through  reciprocal  the of  give the rupture  i s the observed  velocity  f o r each s t a t i o n and resulting  the  length.  point  i s the cosine of the  s t a t i o n d i v i d e d by t h e p h a s e  give the rupture  the y - i n t e r c e p t w i l l  the  c o n s t r u c t e d w i t h one  extremum  (Tmax).  t o Tmax.  forms  The y v a l u e  an  to the p a r t i c u l a r  corresponding  by  one  A graph i s then  f o r each s t a t i o n .  directivity  3.2.3  method,  curve  maximum p e r i o d a t w h i c h  azimuth  reciprocal  t h e p o i n t s c a n be  velocity.  directivity  plotted  negative  through  value  array  of  slope of t h e l e a s t The  reciprocal  of  velocity.  D i f f e r e n t i a l Phases Theory The  effect  of  the  finite  s p e c t r u m c a n a l s o be u t i l i z e d . radiating  f a u l t d i m e n s i o n s on t h e p h a s e  The d i f f e r e n c e i n p h a s e o f waves  i n t o opposite azimuths i s given  from  (5) as  A4>=0(0)-</>(0 + 7r)  = {w(t , - r , / c ) - X , } - { where  |o>(t -r /c)-X } 2  2  2  t , = t i m e f o r t h e wave t o t r a v e l f r o m to the s t a t i o n at 6  the  focus  45  t  2  = t i m e f o r t h e wave t o t r a v e l the  station  from  focus  to  a t 6+ir  r, = the d i s t a n c e to s t a t i o n 0 r = t h e d i s t a n c e t o s t a t i o n 8+ir X, = U b / X ) ( c / v - c o s f l ) X = (wb/X) ( c / v - c o s 0 + 7 r ) . 2  2  T h i s c a n be  rewritten  as, [0  A0=(1/X)(4O,OOO-2r +bcos0)+m+l/4. 1  The  40,000-2r  from the f a c t to  a n d m+1/4  1  t h a t t h e two waves must t r a v e l  reach the recording  wave  train  terms a r e p r o p a g a t i o n terms which  station.  different  By c o r r e c t i n g  for propagation effects  we  arise.  distances  the phase  of  o b t a i n the i n i t i a l  each focal  phase, <j>{ f o c a l ) =<t> ( F F T ) -<p ( d i s p e r s i o n )-<p( d i g i t i z a t i o n ) -#( i n s t r u m e n t ) . In  t h i s p r o c e s s , we  transformed positive).  subtract  seismogram The  from t h e phase  0(FFT)  ^(dispersion)  p a r t of the  a l l phase term  is  advances  the  velocity  (taken  compensation  d i s p e r s i o n w h i c h a wave e x p e r i e n c e s when i t t r a v e l s km w i t h a p h a s e  Fourier as for  a distance  A  C.  ( / • ( d i s p e r s i o n ) = f A/C  where f i s frequency, m e a s u r e d i n km.  The  C i s phase  velocity  and A i s  ^ ( d i g i t i z a t i o n ) term a c c o u n t s f o r t h e d i f f e r e n c e between t h e  origin  t i m e o f t h e e a r t h q u a k e and  b e g i n n i n g of the d i g i t i z i n g  the f i d u c i a l  window was  time at which  chosen.  <£(digitization) = f T  0  where T i s the time d e l a y from the earthquake time t o the s t a r t of d i g i t i z a t i o n . 0  origin  the  46  The 0 ( i n s t r u m e n t )  term i s t h e c o r r e c t i o n f o r t h e phase  response  of t h e s e i s m o g r a p h .  Once  the  difference  focal  phase  f o r each  wave  is  obtained  the  subtracted  out  i s taken. (#> ( f o c a l ) - 0 ( f o c a l ) = A 0 ( f o c a l ) 1  The p r o p a g a t i o n  2  terms i n E q u a t i o n  in o b t a i n i n g the f o c a l phases. phases w i l l  ( 6 ) h a v e been  Therefore  the d i f f e r e n t i a l  focal  be f r o m E q u a t i o n ( 6 ) , A0(focal)=bcos0/X  from which t h e r u p t u r e  l e n g t h , b, c a n be d e r i v e d . b=XA</»( f o c a l ) / c o s 0  Unlike estimate rupture 3.3  the  directivity  of the rupture  which  is  independent  of  the  PROCESSING  The  Acquisition data  were o b t a i n e d  known t o be o p e r a t i n g 1949,  and  records  to  the  by w r i t i n g  relatively World  long  Data Center  t o s t a t i o n s and networks period  variety  in  received.  in  the  stations.  most  cases  type  of  seismogram  I n some c a s e s  full  photographic  copies  Unfortunately,  not  instruments  in  A f o r copies of r e l e v a n t  from l o n g p e r i o d s t a t i o n s i n t h e i r  responding but  length  velocity.  3.3.1 D a t a  was  f u n c t i o n , t h i s method p r o v i d e s an  film  library.  copies  sent  s i z e d c o p i e s were on  microfilm  There by t h e sent, were  a l l of the s t a t i o n s responded,  47  and,  of those  t h a t d i d respond, not a l l sent  Often.important and  static  instrument  Even  reliability  of  questionable. little  when  the  this  quoted  included  information  parameter  Without t h i s  with  the  was  values  period station  included was  the  frequently  i n f o r m a t i o n t h e s e i s m o g r a m s were o f of s t a t i o n s requested  and  their  see Appendix A ) .  In  total,  the  data  seismograph instrument record s t y l e s . information. useful,  not  use ( f o r a complete l i s t  replies,  copies.  parameters such as seismometer  m a g n i f i c a t i o n were  responses.  seismogram  collected  types,  instrument  In a l l cases, The  full  original  sized  useful.  was  the  problem,  too  a menagerie of  p e r i o d s , and hard  records  photocopies,  t e n d e d t o h a v e two p r o b l e m s .  photocopying  represent  provided though  t h e most generally  I n some c a s e s s i m p l y light  and  copy  poor  smudged t o be  A more s u b t l e p r o b l e m w i t h them was t h a t .an edge o r e n d  o f t h e s e i s m o g r a m w o u l d s o m e t i m e s be c l i p p e d o f f . Microfilm limitations  presented  of  the  p o s s i b l e t o make f u l l  problems  department  too.  d a r k room f a c i l i t y ,  s i z e d seismogram c o p i e s  I n s t e a d , a s e r i e s o f p r i n t s h a d t o be made, section and  of t h e seismogram.  taped  Despite seismic  together efforts  t o reassemble to avoid  some o f t h e microfilmed.  An  the  full  of  the  i t was n o t  on o n l y one p r i n t . each  of  T h e s e s e c t i o n s were t h e n sized  only  one  overlapped  seismogram.  i t , skews c o u l d e a s i l y d e v e l o p i n t h e  trace i n the process  seismogram.  Because  of r e c o n s t r u c t i n g  the  full  sized  o c c a s i o n a l p r o b l e m w i t h t h e m i c r o f i l m was t h a t  seismograms  had  their  edges  curled  under  when  48  Of  more t h a n  stations  were  suitable  for  30  eventually use  differential  in  23  and  used.  finding  phases,  used i n d e t e r m i n i n g August  stations originally  and  Only  the  only  requested three  f i v e and  earthquakes,  eight  stations  directivity  were  function  and  eight staions could  t h e s u r f a c e wave r a d i a t i o n  O c t o b e r 31  only  pattern  respectively.  A problem  the  (the  f o r the e i g h t s t a t i o n s used i n t h i s t h e s i s  are  shown i n A p p e n d i x D ) .  that  the  useable  p e r i o d s by  The  signal  s c a t t e r i n g due  low  was  Data The  effectively  after  f o r L o v e and to  between  10 s and  group  began  velocity  crust  and  response.  with  windows.  seismic  tables  300  The  the  c o n s u l t i n g world averaged group v e l o c i t y  km/s  1965).  The  windows  L o v e and  R a y l e i g h wave a r r i v a l s  s.  The  digitizing  and  2.5  km/s  (M=6.2), e a r t h q u a k e s ,  km/s  Rayleigh  waves and  L o v e waves o f t h e A u g u s t 21 were made and  digitizing  were  O c t o b e r 31  of the  the  windows  contain  4.5  for  in  to instrument  R a y l e i g h waves ( K o v a c h ,  chosen  between  bandpassed f o r s h o r t  to inhomogeneities  processing  within  selected  meant  Processing data  records  instruments  power f o r l o n g p e r i o d s  f o r l o n g p e r i o d s by a t t e n u a t i o n due 3.3.2  period  the  w i t h a l l s t a t i o n s was response curves  l a c k of t r u e l o n g  of  be  p l a c e d over  window  for periods  was  typically  f o r t h e A u g u s t 23 and  b e t w e e n 3.9  b e t w e e n 4.5  km/s  (M=8.1) e a r t h q u a k e .  the o r i g i n a l  (M=6.4)  km/s and  4.2  Full  to check the  were  and  and  3.5  km/s  for  size plots faithfulness  digitization.  After d i g i t i z a t i o n ,  the time  s e r i e s was  interpolated  to  a  49  sampling  interval  removed.  The  frequency  domain  the  NS  and EW  parts.  of  time  2  s, and t h e t r e n d and  series  was  then  components  rotated  assumed.  assumed  galvanometer  to  and  into  be  the  For  The  Fourier  program  real  no  radial  feedback  and  These  a narrow  bandpass  were  resulted  from  the  filtered  f o u n d by u s i n g b o t h t h e r e a l  signal  FILTER.  t r a n s f o r m of t h e ground  t r a n s f o r m was  to the  motion.  t h e n t a k e n and t h e e n v e l o p e o f  of the i n v e r s e t r a n s f o r m .  and  imaginary  T h i s e n v e l o p e was  plotted  o f t h e g r o u p v e l o c i t y , and t h e c e n t e r p e r i o d ,  filter  passband.  The  e n v e l o p e was  together,  will  v a r i o u s modes m a k i n g was  multiplied  reflect  the  up t h e s i g n a l .  by  a  factor  of  dimensionally a spectral amplitude. for  a range  represented  of a  center form  of  periods the  so  To,  searched f o r l o c a l  maximums, w h i c h , a s l o n g a s two o r more modes do n o t a r r i v e close  the  processes  Gaussian f i l t e r  inverse Fourier  the  between  next passed t o Herrmann's program  The  of  with  EXSPEC.  t r a n s f o r m e d ground motion which  applied  as a f u n c t i o n  and  tangential  calculated  coupling  seismometer.  f r e q u e n c i e s of t h e F o u r i e r  components  the  Data  u s e o f EXSPEC was  This  into  e l e c t r o m a g n e t i c seismometers,  p e r f o r m e d by H e r r m a n n ' s (1978) p r o g r a m Amplitude  offset  where i n s t r u m e n t c o r r e c t i o n s were a p p l i e d  damping  t h e r e was  the  transformed  I n a l l c a s e s t h e i n s t r u m e n t r e s p o n s e was  critical  3.3.3  the d.c.  too  s p e c t r a l a m p l i t u d e s of the The  peak  4To,  of  so  the  the  result  T h i s p r o c e d u r e was that  the  group v e l o c i t y  envelope was  repeated  resulting  plot  dispersion curve.  50  Essentially given  t h e p l o t shows t h e amount o f e n e r g y  group v e l o c i t y versus  this  filtering  arrivals  and  i s the  the energy's p e r i o d .  ability  obtain their  arriving  to  identify  a  The r e s u l t o f  the  s p e c t r a l amplitudes  at  various  mode  as a f u n c t i o n of  period. F I L T E R a s i t was displayed local  which  the f i l t e r i n g  spectral  maximum  the  displaying  local the  made  and  The  occurred. gave  arrivals  (1978)  of a l l the  spectral  amplitude  While  a l l the in  of  the  needed  local  different  this  method  facts,  maximums  modes.  to  associate  maximum w i t h a s p e c i f i c  mode  f o r amplitude spreading  a  of  i t was and  to  The o u t p u t was  t o i n c l u d e t h e p l o t s mentioned above.  i t easier  geometrical  Herrmann  by t a b u l a t i n g a l i s t  Once i d e n t i f i e d a n d o b t a i n e d , corrected  by  w i t h t h e p e r i o d and group v e l o c i t y f o r  results  therefore modified  amplitude  along maximum  the  written  maximums.  to identify patterns  distinguish  plots  results  amplitude  was l i s t e d  difficult  originally  given  local  These spectral  arrival.  the s p e c t r a l amplitudes  were  d e c r e a s e due t o a n e l a s t i c a t t e n u a t i o n to a selected reference  distance.  Amp(corrected)=Amp(sin(A /A ) exp(-(A,-A )y) a 5  1  where A i s the reference a t t e n u a t i o n f a c t o r g i v e n by 2  2  distance  2  and  7  i s the  7=TT/QTU  with Q=quality factor T=the p e r i o d U=the group v e l o c i t y .  For was  the  August  23 a n d O c t o b e r 31 d a t a ,  1000 km a s o n l y R1 a n d L1 d a t a  the reference  were u s e d .  distance  F o r t h e A u g u s t 22  51  data,  the  reference  approximately and  half  L 3 waves must The  the  distance  radiation  39960  km,  which  is  way b e t w e e n t h e d i s t a n c e t h e R2 a n d R3 o r L2  travel.  corrected amplitudes  directivity  was  function  were t h e n  used i n r a t i o s  to  form  or p l o t t e d a z i m u t h a l l y t o derive the  pattern.  3.3.4 P h a s e D a t a After circling  t h e E a r t h o n c e o r t w i c e t h e wave  t h e A u g u s t 22 d a t a c o n s i s t a l m o s t e x c l u s i v e l y mode,  the  higher  modes  having  mind, t h e phase p a r t of t h e m o t i o n was u s e d w i t h o u t phase t h e o b s e r v e d the from  start the  With t h i s i n  of  to  the  ground  To o b t a i n t h e f o c a l  p h a s e was c o r r e c t e d f o r t h e t i m e  of d i g i t i z a t i o n source  transform  bandpass f i l t e r i n g .  of  of t h e fundamental  been a t t e n u a t e d .  Fourier  trains  d e l a y due t o  a n d t h e p h a s e d e l a y due t o p r o p a g a t i o n  the  receiver.  d e l a y c a u s e d by p o l a r c r o s s i n g s  C o r r e c t i o n s f o r t h e phase  ( A k i , 1966) were a l s o made.  0( f o c a l ) = <£(FFT) -#( d i s p e r s i o n ) -<p( i n s t r u m e n t )-<£( d i g i t i z a t i o n ) By  t a k i n g t h e d i f f e r e n c e o f t h e f o c a l phase  radiated generating  into  opposite  azimuths,  the  rupture  between  waves  length of the  e a r t h q u a k e was d e r i v e d u s i n g e q u a t i o n ( 6 ) .  52  IV.  RESULTS FOR THE M 8.1 EARTHQUAKE OF AUGUST 22  The methods o f d i f f e r e n t i a l a  wave  p a i r o f o p p o s i t e l y t r a v e l i n g waves.  the August a n d R1  22 M=8.1  arrivals  indiscernible  o f f scale  or  both  too  Rayleigh  were o b t a i n e d . obtained  on  and  L3  and  Unfortunately, f o r  R3  s m a l l t o be u s e f u l . clear  and  on  arrivals  either  Only three scale.  stations  At  Tucson  wave (R2,R3) a n d L o v e wave ( L 2 , L 3 )  F o r Pasadena  (PAS),  Love  waves  pairs  (L2,L3)  were  t h e Wood-Anderson i n s t r u m e n t s , b u t t h e R3 a r r i v a l s  were t o o s m a l l f o r R a y l e i g h (HON),  require  e a r t h q u a k e a l m o s t a l l o f t h e s t a t i o n s h a d L1  had t h e r e q u i r e d wave p a i r s (TUO),  phases and d i r e c t i v i t y  only  Rayleigh  waves  waves  to  be  used.  At  Honolulu  (R2,R3) were u s e d a s t h e L 2 waves  were o f f s c a l e . The d i g i t i z e d The  group  velocity  respectively. dispersion  Over  curves  a r e shown i n F i g u r e are  the period  by  (see Figure  looking  expected  i n Figures  range  50-210  17).  flat The  group v e l o c i t y .  group  affected  g e n e r a l ragged The in  17.  valley  mode  was  that  smoothly  close  t o the  chosen  as  The d i s p e r s i o n c u r v e d a t a a p p e a r s  by s c a t t e r i n g w i t h l a r g e h o l e s o f e n e r g y a n d a  appearance.  d i s p e r s i o n c u r v e s do n o t c l o s e l y  Figure  the  I t turned out that the l a r g e s t of the  t h e f u n d a m e n t a l mode a r r i v a l . be  18 a n d 19  fundamental  velocity  16.  seconds  l o c a l e n e r g y maximums f o r a g i v e n p e r i o d was u s u a l l y  to  and  with a gentle  f o r a s e r i e s of a r r i v a l s  v a r i e d and which a r r i v e d w i t h a  15  shown  c u r v e s h o u l d be r e l a t i v e l y  a r o u n d 200 s e c o n d s identified  seismograms  There a r e s e v e r a l  resemble  reasons f o r t h i s .  those  shown  F i r s t , the  53  curves  shown i n F i g u r e  17 a r e  smoothed  s c a t t e r i n g a b o u t t h e smoothed c u r v e s . shorter  period  waves  by  crustal dispersion  power  of  amplitude seismogram  long  of the seismic noise  d i s p e r s i o n curve These c u r v e s data  periods  level,  the  signal  data  points  Second, s c a t t e r i n g of the a f f e c t s the  curves.  Third,  seismographs  means  t e n d s t o be down a t  the  low  that the  the  normal  and hence t h e l o n g p e r i o d p a r t of t h e  i s infected with give the best  a n d i n d i c a t e how n o t h a v i n g  limits  the  inhomogeneities  short p e r i o d p a r t of the at  with  noise.  i n d i c a t i o n of the q u a l i t y true long  period  of the  seismographs  t h e amount o f l o n g p e r i o d s u r f a c e wave a n a l y s i s w h i c h c a n  be d o n e .  54  L2 EW  NS  L3  EW  r  1  i  06  0  S3  i 139  '  105  232  i  i  i  i  i  i  1  1  1  1  1  1  1  1  278  325  371  4|7  4S4  SID  5S7  603  649  696  742  708  83S  881  1 928  T/ME IN SECONDS  NS  R2 EW  flf^Vv/^  NS  R3  vr-\\s •^v-Vt EW  i 0  1  1—'—i  90  181  271  Figure  1  1  1  1  361  452  542  633  i  i  i  ~i  1  r  i  1  1  i  l  723 8)3 904 994 1084 1175 1265 J356 1445 1536 1627 I 717 160< T I M E J N SECONDS  15 - D I G I T I Z E D TUO SEISMOGRAMS FOR THE AUGUST 22 EARTHQUAKE (M=8.1)  There i s a 4.5:1 v e r t i c a l e x a g g e r a t i o n a s t h e t i m e s c a l e h a s been d i v i d e d by 4.5 t o a l l o w p l o t t i n g o f t h e w h o l e s e i s m o g r a m on one p a g e . The s e i s m o g r a m s have been reduced i n scale as w e l l . The amount o f r e d u c t i o n c a n be d e t e r m i n e d by n o t i n g that before r e d u c t i o n t h e t i m e s c a l e m a r k s were 1 cm a p a r t .  R2  R3  i 0  1  1  1  1  1  1  i  95  130  285  379  474  559  664  1  1  1—n  1  1  i  i  i  i  i  i  i  759 854 9<8 1043 1130 1233 1326 1423 1S16 1612 1707 ie02 !697 T I M E IN SECONDS  NS  L2  EW  L3  I 0  I 93  I 186  I 279  Figure  I 372  I 465  I 558  1 652  I T 1 I 1 1 1 1 1 1 1—=—I 1 735 838 931 1024 I 1 17 1210 1303 I 335 14.89 1582 1675 1768 10G1 T I M E IN SECONDS 1  16 - D I G I T I Z E D PAS AND HON SEISMOGRAMS FOR THE AUGUST 22 EARTHQUAKE (M=8.1)  The u p p e r s e t o f s e i s m o g r a m s were r e c o r d e d a t HON, t h e lower s e t on t h e PAS W o o d - A n d e r s o n s . In a l l cases t h e r e i s a 4.5:1 v e r t i c a l exaggeration as the time s c a l e h a s b e e n d i v i d e d by 4.5 t o a l l o w p l o t t i n g o f t h e whole seismogram on one p a g e . The s e i s m o g r a m s h a v e been reduced i n scale as w e l l . The amount of reduction c a n be d e t e r m i n e d by n o t i n g t h a t b e f o r e r e d u c t i . o n t h e t i m e s c a l e m a r k s were 1 cm a p a r t .  56  5.5  RAYLEIGH WAVES 0 MONGOL IA • ASSAM  o  CUTENBERC-BULLEN A CONTI MENTAL CUTENBERC-BULLEN B CONTISENTAL LEHMANNBULLEN A CONTINENT) LEHUANN-BULLEN A OCEANIC JEFF RE rS-BULLENA  y>  "  t o o _j  5  0  UJ  > 5 4.5 O (C o  * 4.0  X  3-5. PERIOD (SEC.}  Figure  17 - T Y P I C A L GROUP VELOCITY CURVES FOR LOVE AND RAYLEIGH WAVES  T h e s e p l o t s show s u r f a c e wave g r o u p v e l o c i t y curves (U) o b t a i n e d by v a r i o u s i n v e s t i g a t o r s . These c u r v e s provide a standard a g a i n s t which the group velocity c u r v e s f o r t h e A u g u s t 22 d a t a c a n be c o m p a r e d ( a d a p t e d from Kovach, 1965).  57  The upper pair of p l o t s are of the R a y l e i g h data r e c o r d e d a t HON. The l o w e r p a i r o f p l o t s a r e o f t h e Rayleigh data recorded a t TUO. The d o t s a r e t h e p o s i t i o n s o f l o c a l maximums i n t h e s p e c t r a l a m p l i t u d e . The s o l i d l i n e i n d i c a t e s t h e e n e r g y a r r i v a l s selected as c o r r e s p o n d i n g t o t h e f u n d a m e n t a l mode. The c u r v e s do n o t c l o s e l y r e s e m b l e t h e s t a n d a r d ones shown i n Figure 17, i n d i c a t i n g how strongly the data are a f f e c t e d by c r u s t a l s c a t t e r i n g a t s h o r t p e r i o d s and instrument response a t long p e r i o d s .  58  Figure  19 - GROUP VELOCITY CURVES FOR THE AUGUST 22 DATA  The u p p e r p a i r o f p l o t s a r e o f t h e Love d a t a r e c o r d e d a t PAS. The l o w e r p a i r o f p l o t s a r e o f t h e L o v e data recorded a t TUO. The d o t s a r e t h e p o s i t i o n s o f l o c a l maximums i n t h e s p e c t r a l a m p l i t u d e . The s o l i d line indicates the energy arrivals selected as c o r r e s p o n d i n g t o t h e f u n d a m e n t a l mode. The c u r v e s do not closely resemble the standard ones shown i n F i g u r e s 17, i n d i c a t i n g how strongly the data are affected by c r u s t a l s c a t t e r i n g a t s h o r t p e r i o d s and instrument response a t long p e r i o d s .  59  4.1  D I R E C T I V I T Y FUNCTION The  d i r e c t i v i t y f u n c t i o n was  spectral  amplitudes  of o p p o s i t e l y t r a v e l i n g  t h e same i n s t r u m e n t . for  instrument  significant accurately averaged  advantage  whole  directivity observed length  when  instrument  P h a s e v e l o c i t i e s and world  paths  function  (see  curves  rupture v e l o c i t y  between the o b s e r v e d  of  waves, a s m e a s u r e d  on  and  correcting  c a l i b r a t i o n were c a n c e l e d  Q v a l u e s were t a k e n B).  were c o m p u t e d a n d  was  theoretical  of  I t was  the  Tmax  extremum  to  longer  extremes i n the short  period  velocity,  the  Vr,  moved  widened t h e s p a c i n g between The and 20).  best  f i t was  similiar maximums  key  t o the and  range.  Tmax  rupture  extreme t o s h o r t e r p e r i o d s  km/s  minimums  curves. of  and  3.5  km/s  f i ttheoretical In  particular,  the observed  i n the t h e o r e c t i c a l  or a s i m i l i a r d i s c r e p a n c y  and  and  265  (see  curves  curves  around  of PAS  100  b i g g e s t d i f f e r e n c e between the o b s e r v e d  local  theoretical  curves the  seconds which  and  seconds and  are  the  a r o u n d 75  curves  km  Figure  t h e same p l a c e w i t h t h e e x c e p t i o n o f  l o c a l maximum i n t h e o b s e r v e d seen  the  new  extremes.  b e t w e e n 3.1  observed  that  introduced  Increasing  f e a t u r e s of the b e s t  appear at a p p r o x i m a t e l y  not  and  match  location  o b t a i n e d w i t h a r u p t u r e l e n g t h of  a rupture v e l o c i t y The  periods  the  rupture  found  i n c r e a s i n g t h e s i z e o f t h e r u p t u r e l e n g t h , b, moved t h e of  not from  compared t o  w h i c h gave t h e b e s t  curves.  a  Theoretical  the c o m b i n a t i o n  found  out,  m a g n i f i c a t i o n s are  Appendix  d i r e c t i v i t y function until and  t a k i n g the r a t i o  T h i s meant t h a t i n a c c u r a c i e s i n  p a r a m e t e r s and  known.  d e r i v e d by  TUO for  is  (Rayleigh), HON.  theoretical  The  curves  DIRECTIVITY _  o  8  o 3 in  con)  w  rr  »—<  H'  0) tt>CO i£> o  itt> 1  O a  3 3 C 03 l O «-t rr <  3* c  rr  ro tn  »—•  C  3  ro  ro in  II 0) to >-i o cn C O r o r r >-t r r  C n> 3yr n c n 0) 3tt>"O O tr < 3 ro n> Qj c n rr  f-•  -3 o D- o CD rr  m  r r  O  •  CJI t — ' M *  0) o  r r p r CD  rt> 3 \0> rr  cn l —  ro  o  DIRECTIVITY  -3 •<  _  8  a  o  Oi n  go  <  >-t CD rr  cn  i  O c  r-h < ro cn  0) 0) C r r 3 I— • Q) O-i r r  II  "a  ^.  n -9 •-«  ^ <  O  M  O  -3 1—4  C  er o  »—i  fO  II  8  c>•n "* «• fc p  i  rr  t—  o  o a  II  o  O o n  8  _  -3  <  rr  3"  5  _  2  o a  B» rr  -  8  •-3  rD'  h-'Tj cn  DIRECTIVITY  -  z  o  z o a  < tn  1=1 o  _ o  8  DIRECTIVITY o  c  5  o o  61  is  t h e s i z e of t h e extremes.  larger  than  the  significantly  extremes  extremes  which  a r e much  appear  to  be  smoothed.  Modification fit  observed  The t h e o r e t i c a l  the data.  of  t h e t h e o r e t i c a l m o d e l was t r i e d  Ben-Menahem a n d  Toksoz  (1962)  given  to calculate  of  s t r e n g t h g i v e n by L = L e x p ( - 2 £ / b ) , w i t h 0<£<b, a n d  for  bilateral  physically a decay The  0  A  variable  source  0  strength  source  seems  r e a s o n a b l e , and t h e t h e o r e t i c a l c u r v e s g e n e r a t e d w i t h  c o n s t a n t £/b = /3=0.75 f i t t h e d a t a s i g n i f i c a n t l y o  effect  extremes  faulting.  f o r a decaying  the  relationships variable  the d i r e c t i v i t y  have  to better  of  the  decaying  (see F i g u r e 21).  source  was  to  flatten  better. a l l the  DIRECTIVITY _  _  t-h O 0 O  C  CD >-3 X 3 "  D " 0 H i n O ft rt 3 0 ) n> t—• D D (t r t r f  <t  fD w O H  l Q T S > 0 J Cu r r II H D " O H • *< » —  cr II  >-"D•  O l r O DJ fD  rx> ro IN oi i n C QJ 3  .  r t  H - 1  C 3 f) i-t iQ n> rt  V mom C O o •-» <~T O O fD <  w  H- (D r t  rt O f - h CD  < C  H*  II w  O rt  O  .  M-  C mo i 3 < ro ?r S t o  3 \ w fD  fl  Mr-t  rr c  ro —  il <-  H II " -  ^ i|  c °  v II  o II  <-. ~ ~  — o  2  - <- «. p  t—i  Z o CO  o a w o n a T-T w  DIRECTIVITY _  ra  o -a »-»  5  -  8  DIRECTIVITY  o  8  5  a z o  •-3 t—4  < CO  "3  w >—<  O  o o  w  *•  -  o o  29  <  «r  O  —  O O  A.  -  8  <  o G  o 3 0) 0>  o o o  o o  >K  CLiO  HO  o  Pi  a m n  o z  0)  DIRECTIVITY  o  1  w  fD  0)  c  8  o  -  •  y-^ 30  63  An  attempt  was  i n t o agreement w i t h using  made  t o b r i n g t h e 490 km a f t e r s h o c k  the d i r e c t i v i t y  function  fault  by  Ben-Menahem a n d T o k s o z ' s ( 1 9 6 2 ) d i r e c t i v i t y r e l a t i o n s h i p s  for  bilateral  faulting.  of  bilateral  rupture  The e f f e c t on t h e d i r e c t i v i t y  (see  Figure  22).  function  was t o smooth a n d d i s p l a c e t h e l o n g  e x t r e m e s a n d damp o u t o r e l i m i n a t e t h e s h o r t e r  to  length  zone  No s u i t a b l e b i l a t e r a l  period  rupture  period  extremes  could  be f o u n d  f i t the data.  Figure  22 - THE EFFECT OF B I L A T E R A L RUPTURE ON D I R E C T I V I T Y FUNCTION  THE  The e f f e c t o f b i l a t e r a l rupture on t h e directivity function i s t o smooth a n d s l i g h t l y d i s p l a c e t h e l o n g period extremes, and e l i m i n a t e the short period extremes.  Since station, using be  the  directivity  was  obtained  an a l t e r n a t e a p p r o a c h t o f i n d i n g  the l e a s t  applied.  this  least  more t h a n one  the rupture  squares technique described  Using  from  i n Section  s q u a r e s method a r u p t u r e  parameters 2.2  could  length of  64  170  km a n d a r u p t u r e v e l o c i t y  1 . 9 km/s was f o u n d  gave a g o o d f i t o f t h e maximum p e r i o d new e x t r e m e s w h i c h d i d n o t e x i s t Figure  23)  determined values  i t was  primarily  found  extreme,  i n the data.  .  These  but  values  introduced  When p l o t t e d ( s e e  t h a t t h e p a r a m e t e r v a l u e s were  b y t h e v a l u e s o f HON a n d w e r e n o t  reliable  f o r the ensemble.  O  16  13  3D  «•  S»  (I  !Q  «0  ^0  |H  110  II*  tJO  |4D  Tmax (Seconds)  Figure  23 - LEAST SQUARES SOLUTION TO THE DATA  The s o l i d l i n e i s the least l i n e corresponds t o the best F i g u r e 20.  squares l i n e . f i tsolution  being  The d a s h e d shown i n  65  For the  the  directivity  f a u l t and  the seismic s t a t i o n ,  the d i r e c t i o n of r u p t u r e though  the  strike there are  depending  upon  t h e o r e t i c a l curves  the  two  which  the data  of r u p t u r e p r o p a g a t i o n f o r t h e A u g u s t 22 M=8.1  This  plane 0's the  Menahem' s ( 1 9 6 7 )  results.  means  from  that  even  i s known f o r a  given  for  a  given  station  rupture progressed. f o r o n l y one  possible  0's  fits  i s determined. earthquake,  t o be u s e d .  between  i s measured c l o c k w i s e  s h o u l d match the d a t a  had  The  of the  two  the d a t a ,  the  In order  a rupture  to f i t  direction  T h i s i s i n agreement w i t h  Ben-  D I F F E R E N T I A L PHASES The  traveling  differential wave  each s t a t i o n  given  (see Table  station  suprising  curves. these  phase a t a g i v e n p e r i o d  pairs  the d i f f e r e n t i a l  not  possible  direction  to the northwest  4.2  0,  fault  By n o t i n g w h i c h of t h e two  direction  the a z i m u t h a l angle  propagation.  of  earthquake  0's.  function  was  between  opposite  o b t a i n e d a t a v a r i e t y of p e r i o d s f o r  I I I ) . The  fault  lengths  obtained  from  p h a s e method show c o n s i d e r a b l e s c a t t e r w i t h i n  f o r a l l the s t a t i o n s except  PAS.  This scatter  i n v i e w o f t h e r a g g e d a p p e a r a n c e of t h e  B e c a u s e o f t h e r e l a t i v e c o h e r e n c e of  r e s u l t s were s e l e c t e d a s t h e most  t h e . PAS  reliable.  a is  dispersion results  66  PAS  TUO (LOVE) DIFFERENTIAL PHASE  PERIOD  0.2336 0. 1984 0.8330 0. 3796 0.2751 0.2122 0.2383 O.2128 0. 1781 0.2783 0.3016 0.2693 0.2940 0.3813 0. 3898  90. 3S 93. 00 99. 10 102. 40 103. 93 113. 78 118. 13 122. 88 128. 00 139. 64 146. 39 1 53. 60 161 68 170. 67 192. 00  AVERAGE  LAMBDA  FAULT LENGTH  417. 92 430. 78 460. 34 476. 88 494. 37 334. 11 333. 63 379. OS 604. 48 663. 76 698 08 736. 18 778. 64 826 42 941 76  114. 24 91. 41 410. 33 293. 63 143. 33 121. 20 141. 66 131. 79 113. 13 197. 74 223. 18 212. 08 244. 83 337. 24 394. 09  FAULT LENGTH-  225.  LAMBDA  FAULT LENGTH  90. 33 96. 00 99. 10 102. 40 103. 93 109. 71 113. 78 118. 13 122. 88 128 00 133. 37 139. 64 170. 67 192, 00  0. 7330 0. 4383 0.4107 O.6174 0.6072 0. 4801 0. 3482 0.2207 0. 1353 0.2763 0. 7233 0.2314 0. 1203 0.2193  417. 92 443. 40 460 34 476. 88 494. 57 313. 60 334. 11 355. 63 579. 03 604. 48 632. 69 663 . 76 826. 42 941. 76  346. 39 230. 96 214. 01 333. 14 339. 78 279. OO 331. 28 138. 73 101. 77 189 11 317. 92 188 82 112 65 233 67  HON  DIFFERENTIAL PHASE  LAMBDA  90 35 93. 09 96. 00 99. 10 102 40 105. 93 109. 71 113. 78 118. 15 122 88 133 57 139 64 1 33 60 170. 67 192. 00  0. 8717 1.0122 0.3641 0. 7663 0. 7548 0. 7158 0. 6666 1. 1638 0.3775 0.7416 0 9765 0. 3719 1.2902 0. 8729 o. 2948  368. 63 692. 80 380 43 830 24 393. 28 308. 70 407 0 3 672. 43 421. 73 686. 33 437 36 673. 30 434 60 653. 31 473 05 1186 98 492. 99 401. 20 514 71 822 94 365 04 1189 54 394 11 732 51 660 40 1837. 02 736. 58 . 13S6. 29 862 73 348. 33 F A U L T LENGTH**  DIFFERENTIAL PHASE  AVERAGE  TUO (RAYLEIGH)  AVERAGE  PERIOD  21  PERIOD  (LOVE)  FAULT LENGTH  FAULT LENGTH"  2 3 4 . 10  (RAYLEIGH)  PER 100  DIFFERENTIAL PHASE  LAMBDA  FAULT LENGTH  90 33 93. 09 96. 00 99. 10 103. 93 113. 78 118. 13 122 88 128 00 133. 37 139. 64 161. 6B 180. 71 192. 00  0.9164 1.3652 0.9997 1.2905 0.5259 0.8785 0.7201 O.4773 1.1336 0.9651 O.1379 O.4668 0.2663 o.6498  368. 63 380. 43 393 28 407. 03 437. 36 473. 05 492 99 514. 71 538. 62 363. 04 394. 11 696. 39 791. 19 862. 73  351. 49 972. 03 641. 85 837. 33 373. 66 678. 42 379. 49 401. 08 996. 74 690. 23 133. 17. 330. 66 344. 24 913. 18  AVERAGE FAULT LENGTH- 634. 84  8 4 1 . 59  T a b l e I I I - DIFFERENTIAL PHASE FAULT LENGTHS  The for  poor  consistency  of the r e s u l t s  the d i f f e r e n t i a l phases  (e.g.,  Kanamori,  differential  1970)  phases  only  within  i s not s u p r i s i n g .  i t  is  frequently  be a p p l i e d  a  given  In the  station  literature  recommended  to periods  greater  than  that 200  67  seconds.  These recommendations,  long period instruments that  crustal  with periods likely  b a s e d on r e s u l t s  of the world  scattering  wide  derived  from  s e i s m i c network,  imply  s t r o n g l y a f f e c t s t h e c o h e r e n c y o f waves  s h o r t e r t h a n 200  seconds.  t o be f u r t h e r a c c e n t u a t e d  The  l a c k of c o h e r e n c e i s  i f one d o e s n o t have t h e l u x u r y  of a t r u e l o n g p e r i o d insrument but  must  with  seconds.  a  peak  response  seconds c r u s t a l  scattering  for periods longer period  around  than  seismographs  12  strongly affects  100  seconds  a r e so p o o r  i n n o i s e and, hence,  i s incoherent  short.  f r o m PAS  The  results  F o l l o w i n g the suggestion the d i f f e r e n t i a l  was  taken.  phases  Though t h e r e was  the w e i g h t i n g ,  I tried  to  At p e r i o d s ^  of  the  100  while short  t h a t t h e s i g n a l becomes b u r i e d at long periods  as  internal  well  as  consistency  1978).  lengths  no s p e c i f i c make  instruments  the coherence,  of A k i ( l 9 6 6 ) , a  fault  on  the response  show t h e b e s t  and a g r e e w i t h Ben-Menahem ( 1 9 6 7 ,  of  rely  the  weighted  average  from a l l four s t a t i o n s formula  for  determining  weighting  an  individual  station  received  c o r r e s p o n d t o the i n t e r n a l c o n s i s t e n c y of the  results  of  station.  HON=0.5, rupture  that  TUC  (Love)=0.25,  With and  the TUC  km was  derived.  of  ( R a y l e i g h ) = 0 . 2 5 an  l e n g t h , from the w e i g h t e d average  p h a s e s , o f 358  weighting  of  the  PAS=1.0, average  differential  68  4.3 ERROR ANALYSIS The  attempts  surface  in  this  thesis to extract  information  from  waves p e r h a p s d e m o n s t r a t e one t h i n g more t h a n a n y o t h e r :  quality  seismographs  essential  with  f o r obtaining  appropriate  response  d e t a i l e d information  about  seismographs  are  earthquake  source parameters.  O l d low  many  i n t o t h e seismogram and unduly i n f l u e n c e t h e  uncertainties  power  curves  introduce  too  subsequent a n a l y s i s . If with  t h e f u n d a m e n t a l mode  i t s amplitude  crustal  scattering,  and then  arrival  i s correctly  phase u n a f f e c t e d the  error  1) e r r o r 2)  T  the  possible  i n t h e instrument phase response  improper  by s e i s m i c in  d i f f e r e n t i a l p h a s e w o u l d come f r o m t h r e e  identified n o i s e and calculated  sources:  correction  0  3) wrong p h a s e v e l o c i t i e s u s e d . The  e f f e c t on t h e r e s u l t s o f ( 1 ) w o u l d d e p e n d on how f a r o f f t h e  true of  instrument  r e s p o n s e was f r o m t h e c o r r e c t i o n .  20% i n s t r u m e n t  these  older  radians  response  instruments.  uncertainty This  seems  reasonable  implies a possible  o f t h e d i f f e r e n t i a l .phase r e s u l t s .  An e r r o r  would l e a d t o a 5f/»=ajAt = 27rfAt e r r o r An  error  i n radians.  i n t h e phase v e l o c i t y , c, would l e a d t o , 60=6 (cor/c ) =ur 3 c / c  where  -3C = e r r o r  inc  2  error  An e s t i m a t e  i n radians  for  20% e r r o r i n At  in  T  0  69  c = phase v e l o c i t y r = l e n g t h of p a t h o v e r w h i c h t h e p h a s e v e l o c i t y in e r r o r .  The  fact  crustal are  is,  however, t h a t the d a t a  s c a t t e r i n g and  difficult  is  are g r e a t l y i n f l u e n c e d  seismograph n o i s e , the e f f e c t s  to assess,  and  of  w h i c h as a r e s u l t make an  by  which overall  error estimate i m p r a c t i c a l . Estimates  of t h e d i r e c t i v i t y  same d i f f i c u l t i e s fault  length  scatter best 4.4  and  of the  the  For  of t h e  SEISMIC MOMENT AND  both  directivity  r e s u l t s among t h e  indication  The was  as a b o v e .  u n c e r t a i n t y are the  1949  r e s u l t s of  Ben-Menahem  explicitly  earthquake.  d e r i v e d the d i r e c t i v i t y  potency. rigidity true  these  results obtained  long  I c h o s e t o use period  of c r u s t a l  the  and  what he  seismic  (1978).  differential called  the  o v e r mine as he  of  200  him  f o r a l l o f my  of the  s i g n a l was  Figure  A p p e n d i x D t o compare t h e  Ben-  equalized  instruments  at the  was  by  noise  where  long  a  the the get  period  meant level  r e s p o n s e of the  the  using  I c o u l d not  at t h i s  this  phases,  t o measure  seconds  i s minimized.  the amplitude  earthquake  s e i s m i c moment  s u r f a c e wave a m p l i t u d e  response curves  24 and  the  s e i s m i c moment f o r  which allowed  at a p e r i o d  inhomogeneities  a good m e a s u r e o f t h e since  h i s data  instrument  s u r f a c e wave a m p l i t u d e effect  determine the  T h i s potency i s r e l a t e d to the n.  the  results.  Queen C h a r l o t t e  Menahem d i d n o t  using  s i z e of  STRESS DROP  c a l c u l a t e d u s i n g the  and  the  the  phase  s t a t i o n s i s probably  u n c e r t a i n t y of the  s e i s m i c moment f o r t h e  He  to  differential  function,  three  subject  PAS  that (see  70  400  300  ZOO  100-  4 0  6.0  8.0  10.0  sic Figure  24 - RESPONSE CURVE FOR THE PAS STRAIN METER  (Adapted strain  120  100  meter  f r o m Ben-Menahem, 1978) with  the response of the instruments  used  in this  thesis). The  s e i s m i c moment i s d e r i v e d  correcting  f o r the  from s p e c t r a l  f i n i t e n e s s of the rupture  from t h e d i r e c t i v i t y  results),  or  transfer function.  Rayleigh  crustal  Ben-Menahem i n  obtaining  amplitudes process  r a d i a t i o n p a t t e r n , and  the  equalized  by  (derived the  Love  A l l o f t h i s was done by potency.  Using  his  r e s u l t s a n d ^=3.2x10'' d y n e / c m , a s e i s m i c moment Mo= 1 . 15 x 1 0 2  dyne  cm  Geller  was  found.  and Kanamori's  T h i s c o m p a r e s w e l l t o t h e Mo f o u n d (1977)  relation,  Mo=1.23xl0  where S i s t h e f a u l t  2 2  x Si  surface area  s  i n km . 2  Z 8  using  71  W i t h S = ( 4 9 5 ) x ( 2 0 ) an Mo o f 1 . 2 x 1 f J  i s obtained.  2 8  U s i n g Gutenberg and R i c h t e r ' s  (Richter,  1958)  formula f o r  s e i s m i c energy E , LogE =11.8+1.5Ms For and A k i ' s  Ms=8.1  F o r Ms>6.5  E =8.9 x 1 0  2 3  ergs,  f o r apparent s t r e s s drop a ,  (1966) r e l a t i o n a  = r}d=u.E  where /i=rigidity E = s e i s m i c energy r?=efficiency c o e f f i c i e n t i n t o seismic energy. a=average s t r e s s ,  /M  0  y  the  apparent  of s t r a i n energy  s t r e s s d r o p was c a l c u l a t e d  t o be a =25 b a r s .  a v e r a g e d i s p l a c e m e n t a l o n g t h e f a u l t c a n be the  standard  expression  released  n  derived  using  The the  f o r t h e s e i s m i c moment ( K a n a m o r i a n d  Anderson,1975). M =MLWD 0  L=fault length W=fault w i d t h D=average d i s p l a c e m e n t a l o n g t h e f a u l t  Solving  t h i s equation f o r the average displacement using a  w i d t h o f 21 km one o b t a i n s ,  f o r an o v e r a l l  D=6.5 m  f o r L=265 km  D=3.5 m  f o r L=495 km  a v e r a g e d i s p l a c e m e n t o f D=5.0 m.  fault  72  I f we f o l l o w  Ben-Menahem  (1978)  and  break  the  seismic  moment i n t o t h e sum o f t h e moments g e n e r a t e d by t h e d i s p l a c e m e n t along  two  different  parts  of  the fault,  which t h e displacement i s l a r g e s t and  thepart  (the d i r e c t i v i t y  the part f o r fault  f o r which t h e displacement i s t h e l e a s t  of t h e r u p t u r e w h i c h i s b e y o n d discussion  namely  section  thed i r e c t i v i t y  length)  ( that  length;  part  see t h e  o f t h e Summary a n d D i s c u s s i o n c h a p t e r f o r an  explanation of t h i s ) ,  t h e n we c a n w r i t e  the r e l a t i o n  f o r the  s e i s m i c moment a s , M =MW(L,D +L D ). 0  If  1  2  2  we assume D =4.96 m, L . ^ 2 6 5 km, a n d L = ( 4 9 5 k m - 2 6 5 k m ) = 2 3 0 km, 1  t h e n D =1.7 m. 2  whole  fault  2  T h e r e f o r e , t h e average  displacement  along the  i s 4.96 m, b u t a l o n g t h e e n d s o f t h e f a u l t  only  1.7  m. The between fault  stress  drop  was  calculated  stress  drop  and  t h e s e i s m i c moment f o r a  (Kanamori  and Anderson,  using  the  relationship strike-slip  1975),  M =(TT/2)W LAO-. 2  0  The  s t r e s s d r o p , A a , was f o u n d t o be  energy  was a l s o c a l c u l a t e d  The  strain  u s i n g Kamamori a n d A n d e r s o n ' s  (1975)  r e l a t i o n s h i p between t h e s t r a i n average  Aa=34  bars.  e n e r g y , AW, a n d t h e a p p a r e n t a n d  stress, AW=(7rW L/2M)Aad. 2  The  strain  e n e r g y was f o u n d t o be  AW=9.5  x  10  2 3  a l l o w e d t h e e f f i c i e n c y c o n s t a n t TJ t o be d e t e r m i n e d : . T?=E /AW=0.93 S  The  average  s t r e s s was c a l c u l a t e d :  .  ergs.  This  73  0=0^/77=26 . 9 b a r s . And  finally  the f r i c t i o n a l  0^ =a-o = 1 .9 b a r s  a  +  was c a l c u l a t e d ,  (Kamamori a n d A n d e r s o n ,  a  Ben-Menahem  stress,  1975).  (1978) d e r i v e s a f a u l t d e p t h o f 40 km f o r t h i s  earthquake, i n stark contrast  t o t h e r e s u l t s of Horn  ( 1 9 8 4 ) , a n d Hyndman a n d E l l i s  (1981) who s u g g e s t a c r u s t a l  in the area of only was  derived  by  16-21 km.  assuming  of  m. 495  the fault  l e n g t h t o be 265 km w i t h an chosen  to  I f an a v e r a g e d i s p l a c e m e n t o f 4.96 m a n d a f a u l t km  is  used,  depth  Ben-Menahem's v a l u e f o r t h e d e p t h  average displacement along t h e f a u l t a r b i t r a r i l y 3.5  et. a l .  his calculations  consistent with the estimated c r u s t a l  will  depth.  yield  a  be  length depth  74  V.  RESULTS FOR THE EARTHQUAKES OF AUGUST 23 AND OCTOBER 31 As  mentioned  originally surface  requested,  wave  earthquake The  out  of  more  pattern  f o r the  and o n l y e i g h t f o r t h e October  with  calibration  an  August  instrument  twenty  c u r v e s a r e shown i n F i g u r e s 30-36.  c u r v e s g i v e an i n d i c a t i o n  of  fundamental  the  The  quality  mode a r r i v a l  data  have  had  identify  as  OTT.  mode  long  to  Therefore,  arrival  These d i s p e r s i o n the  was c l e a r l y  f o r almost  disperse the  and  discernible  and  s e p a r a t e as those  dispersion  curve  s e e n by t h i s  The r a p i d a n d s t e a d y  a l l group v e l o c i t i e s  o f f s o much t h a t i n c o r r e c t i n g  only noise  For  ( F i g u r e s 30, 3 1 ) .  i s being  amplified.  rise  used  to  filtering f o r OTT  s t a r t i n g around  s e c o n d s i n d i c a t e s t h a t b e y o n d 55 s e c o n d s i n s t r u m e n t dropped  data.  The d i f f e r e n c e b e t w e e n DBN  i s more c l e a r l y  t e c h n i q u e a t DBN t h a n a t OTT. in amplitude  velocity  e x p l a i n e d by n o t i n g t h a t t h e waves a r r i v i n g a t DBN  twice  arriving at  31  f r o m A u g u s t 23 OTT ( F i g u r e 31) d o e s n o t  d i s p l a y a n y c l e a r mode a r r i v a l . OTT i s p a r t l y  group  of  o u t t o 60 s e c o n d s f o r t h e A u g u s t 23 DBN d a t a the  magnification  s e i s m o g r a m s f o r t h e A u g u s t 23 a n d O c t o b e r 25-29.  and  percent.  dispersion  contrast,  parameters  In general, the instrument  a r e shown i n F i g u r e s  In  (M=6.4)  instruments  accuracy.  the  23  was t h e l a c k o f t r u e l o n g p e r i o d  earthquakes  instance,  stations  earthquake.  u n c e r t a i n t y of both  digitized  30  31 (M=6.2)  was e s t i m a t e d a s known o n l y t o w i t h i n The  than  o n l y f i v e c o u l d be u s e d i n d e t e r m i n i n g t h e  radiation  g e n e r a l problem  coupled  earlier,  55  response has  f o r instrument  response  FRE  II  II  — I II  -  I III  I III  I IX  1  I l «  I III  I IK  III  III I H I I I I 1)1 7 0 I I S H I III T i n t IH S t C O K O S  III  )0« l i t  III  —r—  111  ill  111  111  at  < I I «ti  ui « M  SJP  I I I• '• TIME  » • '1  P i l l  I• I  I  »  »  »  •  »  •  I  I. I 1500  IN SEIOIV/dj  DBN  1 • • ; 0  T i n t .  Figure  • • • • • • IN S E C O N D ; ,  25 - D I G I T I Z E D SEISMOGRAMS FOR THE AUGUST 23 EARTHQUAKE (M=6.4)  The u p p e r t r a c e f o r FRE a n d DBN was r e c o r d e d on t h e vertical seismograph, t h e m i d d l e t r a c e on t h e n o r t h s o u t h seismograph, and the lower t r a c e on t h e e a s t west seismograph. The S J P s e t o f s e i s m o g r a m s h a s no v e r t i c a l , and, hence, t h e upper t r a c e corresponds to the n o r t h - s o u t h seismogram, and t h e lower t r a c e t o t h e east-west seismogram.  (725-  76  OTT  31fc <W> SiH W TIME. jN s e c o A / 0 5  *i  W  110  TUO  I—i  o  Figure  r  SI  T — I — i — T " r - r i  "OS"  IS!  2iD  i  •  i  i  »  »  »  z«2 30' 3tT '1 T I M E <IJ i ZC°t"> i g  '  •  V?2  *  '  S"l</  '  '  577  '  42.1  26 - D I G I T I Z E D SEISMOGRAMS FOR THE AUGUST 23 EARTHQUAKE (M=6.4)  The u p p e r t r a c e f o r OTT c o r r e s p o n d s t o t h e n o r t h - s o u t h seismogram, and the lower trace the east-west seismogram. The o r d e r o f t h e s e i s m o g r a m s f o r TUO i s the same a s OTT e x c e p t t h a t t h e t o p s e i s m o g r a m i s a v e r t i c a l seismogram.  HON  • i  • r  t  • i  i  A^ATvVWvW^/^^ i  i  I  i  6  i  i  I  I  I'  1  i  i  A, 1  i  i  i  i  i  i  i  i  i  i  i  i  l  '  t  i  l  i  l  t  i  i  i  i  11*  T i n t IN StCOKOS  DBN  T I M E Ikl 5 EloUOf  ,  SJP  Figure  27 - D I G I T I Z E D SEISMOGRAMS FOR THE OCTOBER 31 EARTHQUAKE (M=6.2)  The u p p e r t r a c e f o r DBN i s t h e v e r t i c a l seismogram, the middle t r a c e t h e n o r t h - s o u t h seismogram, and t h e lower t r a c e t h e east-west seismogram. The o r d e r i n g o f t h e t r a c e s f o r HON a n d S J P i s t h e same a s f o r DBN e x c e p t t h a t t h e r e i s no v e r t i c a l s e i s m o g r a m .  78  PAS  i 0  —  i — i — i — 28 56 83  i — 111  i  — 139  i  — 167  i 194  i — i — 222 2S0  i 278  i — i — 30 5 33 3  TIME  i 36 1  t 389  JN 5 E X 0 N 0 S  i 4!6  i 44".  i 472  i 500  i 527  i 55S  i 583  i 611  i 638  BOZ  —  i 52  —  i — 105  i — 157  \  — i — i — i 2J0 262 J15  — 367  ~I 525  TJME^JN  I  I  I  I  I  I  I  I  I  577  630  68?  735  787  840  892  945  397  SECONDS  ! 1050  HAL  I 64  Figure  I 128  I 191  I 255  I 319  I 383  I 447  I 51]  I 57 4  TJME  I 638  JN  I 702  I 7G6  SECONDS  I 830  I 833  I 957  I 1021  I 1085  1 1)49  1 12J2  28 - D I G I T I Z E D SEISMOGRAMS FOR THE OCTOBER 31 EARTHQUAKE (M=6.2)  The upper trace f o r PAS i s t h e v e r t i c a l s e i s m o g r a m , the m i d d l e t r a c e t h e n o r t h - s o u t h seismogram, and t h e lower t r a c e t h e east-west seismogram. The o r d e r i n g o f the traces f o r BOZ a n d HAL i s t h e same a s f o r PAS e x c e p t t h a t t h e r e i s no v e r t i c a l s e i s m o g r a m .  1 1276  i 666  i 694  79  SLT  —r  — i  35  1  1  Ift JM  r  -  237  — i  285  1  332  1  1  1  1  1  1  1  380 427 475 522 563 «JT TJME  JN S E C O N D S  OTT  48  96  144  132  240  28fl  336  38 4  432  TJME  480  JN  528  S7G  624  672  720  "768  816  864  312  SECONDS  F i g u r e 29 - D I G I T I Z E D SEISMOGRAMS FOR THE OCTOBER 31 EARTHQUAKE (M=6.2) F o r b o t h SLT a n d OTT t h e u p p e r trace i s the northsouth seismogram, and t h e lower t r a c e i s t h e east-west seismogram.  960  80  PERIOD  PERIOD 6  13  21  28  36  "3  50  S8  6S  73  80  0  13 21  28  36 13 SO  58 6S 73  60  TUC UT Figure  30 - GROUP VELOCITY CURVES FOR THE AUGUST 23 LOVE WAVE DATA  The dots i n d i c a t e t h e p o s i t i o n s o f l o c a l maximums o f the s p e c t r a l a m p l i t u d e . The s o l i d l i n e i n d i c a t e s t h e energy arrivals selected as c o r r e s p o n d i n g t o the fundamental mode. UT means o n l y the tangential component o f t h e s e i s m o g r a m s i s a n a l y z e d .  81  F i g u r e 31 - GROUP VELOCITY CURVES FOR THE AUGUST 23 RAYLEIGH WAVE DATA The dots i n d i c a t e t h e p o s i t i o n s o f l o c a l maximums o f the s p e c t r a l a m p l i t u d e . The s o l i d l i n e i n d i c a t e s t h e energy arrivals selected as corresponding to the f u n d a m e n t a l mode. UR means o n l y the r a d i a l (UR) component of the seismograms i s analyzed. Z means o n l y v e r t i c a l d a t a i s be a n a l y z e d .  82  0  13  21  28  3G^«3'^Po  58  65'  73  PERIOD  80 0  SJP UT  |1  21  28  3G  <n  SO  58  65  SJP UR  F i g u r e 32 - GROUP VELOCITY CURVES FOR THE AUGUST 23 S J P DATA The dots i n d i c a t e t h e p o s i t i o n s o f l o c a l maximums o f the s p e c t r a l amplitude. The s o l i d l i n e i n d i c a t e s t h e energy arrivals selected as c o r r e s p o n d i n g to the f u n d a m e n t a l mode.  73  80  83  HAL UR  Figure  PAS Z  33 - GROUP VELOCITY CURVES FOR THE OCTOBER 31 LOVE WAVE DATA  The d o t s i n d i c a t e t h e p o s i t i o n s o f l o c a l maximums o f the s p e c t r a l amplitude. The s o l i d l i n e i n d i c a t e s t h e energy arrivals selected as c o r r e s p o n d i n g t o the f u n d a m e n t a l mode.  84  F i g u r e 34 - GROUP VELOCITY CURVES FOR THE OCTOBER 31 LOVE WAVE DATA The d o t s i n d i c a t e t h e p o s i t i o n s o f l o c a l maximums o f the spectral amplitude. The s o l i d l i n e i n d i c a t e s t h e energy arrivals selected as c o r r e s p o n d i n g to the f u n d a m e n t a l mode.  85  C  II  '-i  '  21 1  PERIOD  2B 1  36  10 3  SO  58  «  1  1  '  6S '  73  80  '  '  ,  ,  PER/00  21 VT-L  C  in  II  H  3G  03  50  1 , 1  •  1  Sfl  6S  80  7.1  L _ J _  HAL UT  PERIOD IG  43  50  DBN UT  p  C  13 -J  21 I  26 I  36 i  ER!OD 43 i  50 i  S8 i  65 i  BOZ UT  F i g u r e 35 - GROUP VELOCITY CURVES FOR THE OCTOBER 31 RAYLEIGH WAVE DATA The d o t s i n d i c a t e t h e p o s i t i o n s o f l o c a l maximums o f the s p e c t r a l amplitude. The s o l i d l i n e i n d i c a t e s t h e energy arrivals selected as corresponding to the f u n d a m e n t a l mode.  73 i  80  86  PAS UT  OTT UT  F i g u r e 36 - GROUP VELOCITY CURVES FOR THE OCTOBER 31 RAYLEIGH WAVE DATA The d o t s i n d i c a t e t h e p o s i t i o n s o f l o c a l maximums o f the s p e c t r a l amplitude. The s o l i d l i n e i n d i c a t e s t h e energy arrivals selected as c o r r e s p o n d i n g to the f u n d a m e n t a l mode.  87  MECHANISM SOLUTIONS  from  Depending  on  16 s e c o n d s  t o 65 s e c o n d s were u s e d .  observed six  the s t a t i o n ,  azimuthal variation  spectral amplitudes for periods  i n a m p l i t u d e was  l a y e r E a r t h model of N o r t h A m e r i c a  Herrmann  (1978)  program  m e c h a n i s m was  separately best  from  found.  QUESTION,  Love  f i t m e c h a n i s m was  The  period,  plotted.  (see Appendix the  a m p l i t u d e s were c o m p a r e d t o t h e o r e t i c a l fit'  For each  C) and  observed  moment  was  to  uncertainty obtained  the  'best  calculated  waves and t h e n f r o m R a y l e i g h waves.  The  chosen as the mechanism f o r which t h e  two  were  in  coupled with  the  agreement.  Due  'best  the  azimuthal  s e p a r a t e moment e s t i m a t e s f r o m L o v e and R a y l e i g h waves closest  Using a  amplitudes u n t i l a  seismic  the  the in  from  small the  number  instrument  stations  magnifications  the  solutions  t h i s comparison p r o c e s s a r e not m e a n i n g f u l .  f i t ' m e c h a n i s m was August  of  23  or  n o t a 'good f i t ' m e c h a n i s m  the  October  31 e a r t h q u a k e .  The  for  The  either  f i t of t h e  o b s e r v e d s u r f a c e wave r a d i a t i o n p a t t e r n t o t h e b e s t f i t m o d e l i s shown f o r t h e A u g u s t and  f o r the October  Focal  with  31  (M=6.4) e a r t h q u a k e (M=6.2) e a r t h q u a k e  sphere p l o t s of the  F i g u r e 41. for  23  the  The W i c k e n s October  the  earthquake.  few  best  first  motions  i n F i g u r e s 39 and  f i t mechanisms  and Hodgson  31 e a r t h q u a k e  i n F i g u r e s 37 and  (1967)  first  are  shown  motion  38, 40. in  solution  i s a l s o shown i n F i g u r e 41 a l o n g available  for  the  August  23  88  N  2 X  10 1  Figure  37 " THEORETICAL LOVE WAVE RADIATION PATTERN FOR AUGUST 23 EARTHQUAKE The r a d i a t i o n patterns are s c a l e d t o ( i t i n a square 2-3/4 inches on a side. Beneath each r a d i a t i o n pattern the period i s written along with a scale r e l a t i n g the plot size t o u n i t s o f dyne-cm. The radiation pattern shown i s o f t h e b e s t ( i t m e c h a n i s m solution. The d o t s i n d i c a t e t h e o b s e r v e d d a t a . Each dot represents a s t a t i o n , w i t h the azimuth of the dot corresponding t o the s t a t i o n azimuth, and t h e d i s t a n c e o( t h e d o t f r o m t h e c * n t e r o ( t h e r a d i a t i o n p a t t e r n .  THE  89  N  I  4? 2 X  Figure  •  JO  3 8 - THEORETICAL RAYLEIGH WAVE RADIATION THE AUGUST 23 EARTHQUAKE The radiation p a t t e r n s a r e s c a l e d t o f i t i n a square 2-3/4 inches on a s i d e . Beneath each radiation pattern the period i s written along with a scale relating the plot sire t o u n i t s o f dyne-cm. The radiation pattern shown i s o f t h e b e s t t i t m e c h a n i s m solution. The d o t s I n d i c a t e t h e o b s e r v e d d a t a . Each dot represents a s t a t i o n , with the azimuth of the dot corresponding t o the s t a t i o n azimuth, and the d i s t a n c e o f t h e d o t fro« t h e c e n t e r o f t h e r a d i a t i o n pattern.  PATTERN  FOR  90  2 X  10 ~  1  T = 30.0 N  I  2 X T =  30° 40.0  2 X  T = 50.0  N  N  I  2 X  I  30°  T = "70.0  Figure  30°  2 X  J0°  T = 80.0  39 - THEORETICAL LOVE WAVE RADIATION PATTERN FOR OCTOBER 31 EARTHQUAKE The radiation p a t t e r n s a r c scaled t o ( i t i n a square 2-3/4 inches on a side. Beneath each radiation pattern the p e r i o d i s written along with a scale r e l a t i n g the plot aire to units o f dyne-cm. The radiation pattern shown i t o f t h e b e l t ( i t m e c h a n i s m solution. The d o t s i n d i c a t e t h e o b s e r v e d d a t a . Each dot r e p r e s e n t s a s t a t i o n , w i t h t h e a z i m u t h of t h e d o t c o r r e s p o n d i n g t o t h e s t a t i o n a z i m u t h , and the d i s t a n c e o( t h e d o t ( r o a t h e c e n t e r o f t h e r a d i a t i o n pattern.  THE  -91  a 2 X T =  2  X  T =  ]0 —I  34.0  JO  20.0  2 X T =  JO —I  36.0  N  I  2 X  JO  I—L  T =  Figure  50.0  2 X JO ~ I—{ T -  J  60.0  40 - THEORETICAL RAYLEIGH WAVE RADIATION PATTERN THE OCTOBER 31 EARTHQUAKE The r a d i a t i o n p a t t e r n s a r e s c a l e d t o f i t i n a square 2-3/4 inches on a side. Beneath each r a d i a t i o n pattern the p e r i o d i s w r i t t e n along with a scale r e l a t i n g the p l o t site to units o f dyne-cm. The radiation pattern shown i s o f t h e b e s t f i t m e c h a n i s m solution. The d o t s i n d i c a t e t h e o b s e r v e d d a t a . Each dot represents a s t a t i o n , with the azimuth of the dot c o r r e s p o n d i n g t o the s t a t i o n a z i m u t h , and t h e d i s t a n c e of t h e d o t f r o m t h e c e n t e r o f t h e r a d i a t i o n p a t t e r n .  FOR  F i g u r e 41  - FOCAL MECHANISMS OF THE AUGUST 23 AND 31 EARTHQUAKES  Dipicted in this figure are lower hemisphere focal sphere p r o j e c t i o n s of: I) The poorly defined P-nodal s o l u t i o n of W i c k e n s and Hodgson ( 1 9 6 7 ) f o r the October 3) e a r t h q u a k e ( M - 6 . 2 ) , 2) The very poorly constrained best f i t surface wave mechanism solution for the October 31 earthquake, 3) The well defined P-nodal s o l u t i o n of R o g e r s ( 1 9 8 3 ) f o r the August 22 (M-8.1) earthquake. 4) The very poorly constrained best f i t s u r f a c e wave m e c h a n i s m solution for the August 23 e a r t h q u a k e ( M - 6 . 4 ) , 5) S u g g e s t e d p o s s i b l e n o d a l planes from the few f i r s t motion readings available for the A u g u s t 23 e a r t h q u a k e . Note that the p o s i t i o n of the pressure and tension axes for best f i t surface wave m e c h a n i s m s c a n be r e v e r s e d , a s r i g h t - l a t e r a l or leftlateral s t r i k e - s l i p motion c a n n o t be d i s t i n g u i s h e d from amplitude data alone (Herrmann, 1978).  OCTOBER  93  the  The c o r r e c t s u r f a c e wave s o l u t i o n  must be  first  focal  motion  data  radically  as t h e rupture  is  as  used  unless  the  progressed.  a constraint,  compatible mechanism  I f the f i r s t  changed  motion  t h e s u r f a c e wave m e c h a n i s m s  with  data  obtained  f o r t h e A u g u s t 23 e a r t h q u a k e must be w r o n g . The c o n c l u s i o n drawn f r o m t h i s s t u d y using the azimuthal focal history  mechanism  s u r f a c e wave r a d i a t i o n  is  ineffective  when s t a t i o n c o v e r a g e was  instrument  calibrations  poor.  for  i s t h a t t h e method  pattern t o obtain the  this  sparse  of  and  area  and p e r i o d i n  the  quality  of  94  VI. 6.1  directivity  analyzed  at three  rupture  propagating  rupture  rupture  other In  velocity  stations. to the  who  general,  The  rupture  are  appears  from  does not  agree w i t h the  the  It  this  l e n g t h and data  rupture  surface  the  is  s  good  3.1  the  1949 and  as are  indicate l e n g t h of  km/s  velocity  to  km  the  In  earthquake functions  d e r i v e d from this as  the  apparent  being  too  To  for  some  rupture  nevertheless,  the  incompatible  with  fact,  w h i l e my  data  Ben-Menahem's a n a l y s i s  Pasadena  instrument.  phases f a u l t  for  i s usually  of the d a t a .  are  other  km/s.  phase  results  t h a t they km.  These  crust.  resolve  uncertain;  at  velocity  Charlotte  490  km  with  the p r e c i s e values  490  265  t o 3.5  differential  were  unilateral  km/s.  i n the  Queen  instruments,  made u s i n g  3.5  rupture  rupture  l e n g t h of  long period  f o r the d i f f e r e n t i a l  the  the poor q u a l i t y  to short period  ), a t r u e  a  agreeement  s u r f a c e wave  velocity  wave f a u l t  and  the  tempting  true,  t h i s e a r t h q u a k e was  (Tg=70 km  be  are good enough t o  were l i m i t e d of  may  in  range of  fault  i n f l u e n c e d by  phases  imply  s h e a r wave v e l o c i t y  c o n f l i c t by d i s m i s s i n g t h e  extent  km/s  directivity  zone.  l i m i t e d and  3.1  that  l e n g t h of  derived  aftershock  results  have found t h a t  l e s s than the  differential  n o r t h w e s t "for a p p r o x i m a t e l y  i s i n the  i t  and  The  between  results  earthquakes  slightly  function  velocity  investigators  a  DISCUSSION  DISCUSSION The  a  SUMMARY AND  length  125-277 s e c o n d s show e x c e l l e n t c o h e r e n c e and  EW His  strain-meter r e s u l t s of  i n the p e r i o d c a n n o t be  265  range  dismissed  95  a s a f f e c t e d by n o i s e . The  r e l a t i o n s h i p between a f t e r s h o c k zone and f a u l t  l e n g t h c a n be s e e n more c l e a r l y i n v e s t i g a t e r s have o b t a i n e d . determination are  rupture  by l o o k i n g a t t h e r e s u l t s  other  Other examples o f source  parameter  from d i r e c t i v i t y and d i f f e r e n t i a l phase  functions  l i s t e d i n Table IV. DIRECTIVITY FAULT LENGTH (KM)  Chile 725 May 2 2 , 1960 M=8.5 Kamchatka 700 Nov. 4, 1952 M=8.25 Mongolia 560 Dec. 4, 1957 M=8.0 San F r a n c i s c o 240 J u n e 6, 1906 M=8.0 Alaska 350 J u l y 10, 1958 M=8.0 Kurile Islands O c t . 13, 1963 M=8.0 Sanriku 270 M a r c h 2, 1933 M=8.0 Table  DIFFERENTIAL FAULT LENGTH (KM)  AFTERSHOCK FAULT LENGTH (KM) 1000  REFERENCE Press e t a l . (1961)  675  Ben-Menahem a n d Toksoz (1963a)  500  Ben-Menahem a n d Toksoz (1962)  400  Ben-Menahem (1978)  279  380  Ben-Menahem a n d Toksoz (1963b)  250  300  Furumoto (1979)  270  Ben-Menahem (1967)  426  I V - RUPTURE LENGTH FROM D I R E C T I V I T Y PHASES  AND  DIFFERENTIAL  Examples from t h e l i t e r a t u r e of f a u l t l e n g t h s derived from the d i f f e r e n t i a l phases and or t h e d i r e c t i v i t y function. The e x a m p l e s a r e l i s t e d i n d e c r e a s i n g o r d e r of f a u l t l e n g t h .  Clearly wave  t h e r e c a n be a d i s c r e p a n c y rupture  length  and  of 40%  the rupture  between length  the  surface  defined  from  96  aftershocks. difference  Ben-Menahem ( 1 9 7 8 ) , between  the  in  seeking  directivity fault  to  explain  l e n g t h a n d t h e known  s u r f a c e r u p t u r e o f t h e 1906 San F r a n c i s c o e a r t h q u a k e , that  t h e r e i s an e f f e c t i v e  correspond observed  to the f u l l displacement  earthquake around Santa  ranged  fault  rupture.  l e n g t h which  He p o i n t s  P t . R e y e s t o u n d e r 0.5 m e t e r s f o r t h e a r e a  the  fault  radiation  He s u g g e s t s  becomes  that  amplitude  once  may n o t  that  the  f o r t h e 1906  42) •  displacement  l e s s than a g i v e n average  and  of the remaining  phase  i s small  v a l u e , 0.6 rupture  and  does  function  begin'rod.otion.loult'  E  - end  rodianon.fault  L  - end  rupture  JuOn BOutilto  meleri  Out Ml» DISTANCE  JOO I P i ArenO  IOIEMAI FROM  SE  END  OF  THE  FAULT  area  south of the  the  i n f l u e n c e t h e d i r e c t i v i t y and d i f f e r e n t i a l phase FlgUTe  out  a l o n g t h e San A n d r e a s f a u l t  m e t e r s i n t h e 1906 c a s e , t h e a f f e c t the  fault  suggested  f r o m s l i g h t l y more t h a n 6 m e t e r s f o r t h e  Cruz mountains.  along  radiation  the  4 0 0 km I O i l PI OclQotfrj  itmi  F i g u r e 42 - DISPLACEMENT ALONG THE SAN ANDREAS FAULT FOR THE 1906 EARTHQUAKE T h i s f i g u r e shows t h e r e l a t i o n s h i p o f t h e d i s p l a c e m e n t along t h e San A n d r e a s f a u l t t o t h e d i r e c t i v i t y f a u l t length. The d o t s represent t h e measured offset d i s p l a c e m e n t a l o n g t h e f a u l t ( f r o m Ben-Menaham, 1 9 7 8 ) .  on not  (see  97  If  a similar  between fault  the  explanation  surface  i s used t o e x p l a i n the d i s c r e p a n c y  wave f a u l t  l e n g t h and t h e a f t e r s h o c k  l e n g t h f o r t h e 1949 Queen C h a r l o t t e  implies  that  northwestward  displacement  along  propagation  of  rupture  suggests  occurred  f o r 265 km t o t h e  rupture  displacement  the  the  earthquake, fault  effective  of  continuing,  the  then  was u n e v e n . radiation  that the l a r g e s t displacement north  zone  along  i t The  fault  the f a u l t  epicenter  with  the  but w i t h s m a l l e r o f f s e t , f o r  a n o t h e r 35 km f u r t h e r n o r t h a n d 190  km  to  the  south  of  the  by  f u r t h e r a n a l y s i s of the  epicenter. Information M=8.1  can  be  obtained  A u g u s t 22 e a r t h q u a k e .  information given  In  by Ben-Menahem  particular,  there  is  enough  (1967) t o d e t e r m i n e t h e i n i t i a l  p h a s e , a n d , h e n c e , t h e t i m e f u n c t i o n o f t h e 1949 Queen C h a r l o t t e earthquake. as  The  t i m e f u n c t i o n w o u l d be o f p a r t i c u l a r  i t c a n be u s e d t o d e r i v e t h e r i s e  can  in  turn  (Kasahara, role  in  yield  1981).  time of the rupture,  i n f o r m a t i o n about the i n i t i a l  Rise-time  earthquake  analysis also  engineering  plays  stress an  due  to  the rupture  operating  Thus,- f u r t h e r s t u d y  of t h e source  body  be more s u i t e d t o t h e i n s t r u m e n t  would  Body wave d i r e c t i v i t y obtained  (e.g., Langston,  1978).  use  of  difficult i n 1949.  p a r a m e t e r s t h r o u g h t h e use  and a z i m u t h a l  t o supplement the f i r s t  levels  important  The  parameters proved  the l a c k of long p e r i o d instruments  waves  which  i n which p r e d i c t i o n of s e i s m i c  v i b r a t i o n , a c c e l e r a t i o n and v e l o c i t y a r e d e s i r e d . s u r f a c e waves t o a n a l y s e  interest  of  responses.  radiation patterns could  m o t i o n a n d s u r f a c e wave  be  results  98  As to  w e l l a s s t u d y i n g t h e m a i n 8.1 s h o c k an a t t e m p t was made  derive  t h e mechanism  aftershocks patterns. obtain  using  solutions  their  for  azimuthal  surface  I t was c o n c l u d e d t h a t t h e u s e o f  focal  mechanism  of instrument c a l i b r a t i o n s  In view of t h e l i m i t a t i o n s wave  radiation  two wave  this  pattern,  was  station  are w e l l train  f o rthis  poor.  more  known a n d t h e n t r y t o m o d e l at  that  station  d i s p e r s i o n curves f o r t h e October s u r f a c e waves have n o t been  productive  surface  approach be t o  to  select  can  be  seen,  well  and,  the  entire  surface  (e.g., Kanamori,  1970).  recorded  thus,  this  as  no  clear  collected  hand,  32-35)  d i s p e r s i o n c u r v e s f o r t h e August  .  On  the  other  23 e a r t h q u a k e do d i s p l a y  a r r i v a l s and suggest t h a t s y n t h e t i c  mode  I've the clear  seismogram m o d e l i n g of  t h e s u r f a c e wave f o r m s r e c o r d e d a t DBN m i g h t be s u c c e s s f u l F i g u r e s 29-31) .  The  method m i g h t n o t be data  (see Figures  wave  31 e a r t h q u a k e s u g g e s t t h a t t h e  s u c c e s s f u l when a p p l i e d t o t h a t e a r t h q u a k e u s i n g t h e  mode  area  and t h e  i n obtaining the o v e r a l l  a  to  f o r which t h e i n s t r u m e n t parameters and c a l i b r a t i o n  recorded  arrivals  radiation  sparse  d e t e r m i n i n g t h e s u r f a c e wave f o c a l m e c h a n i s m m i g h t one  largest  technique  solutions i s ineffective  and t i m e i n h i s t o r y when s t a t i o n c o v e r a g e quality  the  (see  99  6.2 CONCLUSION Using  horizontal  thirty-eight 1949 to  seismograms  new a f t e r s h o c k  l o c a t i o n s were  Queen C h a r l o t t e e a r t h q u a k e .  south  490  km.  aftershock  suggested seismic (Kelleher  and  gap  Savino,  to  1975)  d i s t r i b u t i o n a l s o suggests sequence,  zone the  a  and l a t e r The analyzed  directivity  function  three  velocity  stations.  length derived phases, fracture difference first  length  and  between  The  aftershock  in first  shallow  rupture  to the north  epicenter.  differential  phases  The  results  a  unilateral  f o r approximately  265 km a t  - and  imply  3.5  may  km/s.  were  These  (1967,1978).  zone,and t h e r u p t u r e  function  and  differential  be a d i f f e r e n c e b e t w e e n t h e  effective  radiation  n o t e d by Ben-Menahem ( 1 9 7 8 ) f o r  a  the  length.  This  t h e f r a c t u r e l e n g t h and r a d i a t i o n l e n g t h  earthquake, which, l i k e along  the  previously  not e x i s t .  the aftershock  there  the  1906  San  between t h e r a d i a t i o n f a u l t  strike-slip  fault.  occurred  This difference  l e n g t h and t h e f r a c t u r e f a u l t  suggests that the displacement  along  the fault  was  Francisco  t h e Queen C h a r l o t t e e a r t h q u a k e ,  vertical  of  and  from t h e d i r e c t i v i t y that  a  zone  epicenter  shock's  b e t w e e n 3.1 km/s  suggests  t o 190 km t o  1949  variation  t o the northwest  d i f f e r e n c e between  found  the  r e s u l t s a g r e e w i t h t h e r e s u l t s o f Ben-Menahem The  z o n e was  that  concentrating  o f t h e main  rupture propagating a rupture  does  of  Alaska, f o r the  aftershock  implies  north  t o the south  at  a total  time  with the aftershocks  determined  of the epicenter  of the e p i c e n t e r , y i e l d i n g This  at Sitka,  The.aftershock  e x t e n d f r o m 300 km t o t h e n o r t h  the  recorded  was u n e v e n ,  length with  100  the  largest displacement  to the radiation  occurring i n the area that  fault length.  The s e i s m i c moment, energy, strain M=8.1  apparent energy,  event As  stress  average  fault  drop,  stress  and f r a c t i o n a l  displacement,  seismic  drop,  stress,  a n d a r e s u m m a r i z e d i n T a b l e V.  well  their  concluded mechanism  average  s t r e s s were a l l e s t i m a t e d f o r t h e  a s s t u d y i n g t h e main shock  an a t t e m p t  d e r i v e t h e m e c h a n i s m s o l u t i o n s f o r t h e two using  corresponds  that  largest  a z i m u t h a l s u r f a c e wave r a d i a t i o n the  use  of  solutions  is  was  aftershocks  patterns.  technique  ineffective  h i s t o r y when s t a t i o n c o v e r a g e instrument c a l i b r a t i o n s  this  was made t o  to  obtain  I t was focal  f o r t h i s area and time i n  sparse  and  the  quality  poor.  Fault Length F a u l t Depth F a u l t Area Rupture V e l o c i t y Average F a u l t Displacement S e i s m i c Moment S t r a i n Energy Seismic Energy Apparent S t r e s s Drop S t r e s s Drop Average S t r e s s Frictional Stress  495 20 9900 3.1 4.96 1.15 X 1 0 9.5 X 1 0 8.9 X 1 0 25 34 26.9 1.9 2 8  2 3  2 3  km km km km/sec m dyne cm ergs ergs bars bars bars bars 2  T a b l e V - ESTIMATE OF SEISMIC SOURCE PARAMETERS OF THE 1949 QUEEN CHARLOTTE EARTHQUAKE  of  101  BIBLIOGRAPHY 1.  A c h a r y a , H. K. 1979. R e g i o n a l v a r i a t i o n s i n t h e r u p t u r e - l e n g t h magnitude r e l a t i o n s h i p s and t h e i r d y n a m i c a l significance. B u l l e t i n of t h e S e i s m o l o g i c a l S o c i e t y of A m e r i c a , 6 9 , pp. 2063-2084.  2.  A k i , K. 1966. G e n e r a t i o n a n d p r o p a g a t i o n o f G waves f r o m t h e N i i g a t a E a r t h q u a k e o f J u n e 16, 1964. B u l l e t i n o f t h e E a r t h q u a k e R e s e a r c h I n s t i t u t e , 44, p p . 2 3 - 7 2 .  3.  A k i , K., a n d R i c h a r d s , P.G. S e i s m o l o g y , V o l . 1. W. H. CA., 557 p p .  4.  Ben-Menahem, A. 1961. R a d i a t i o n o f s e i s m i c s u r f a c e - w a v e s from f i n i t e moving s o u r c e s . B u l l e t i n of the S e i s m o l o g i c a l S o c i e t y o f A m e r i c a , 5 5 , p p . 401-435.  5.  Ben-Menahem, A. 1967. S o u r c e s t u d i e s f r o m i s o l a t e d seismic signals. I n : VESIAC c o n f e r e n c e . on t h e c u r r e n t s t a t u s and f u t u r e p r o g n o s i s f o r understanding t h e source mechanism of s h a l l o w s e i s m i c e v e n t s . U n i v e r s i t y of M i c h i g a n , G e o p h y s . L a b . , p p . 85-108.  6.  Ben-Menahem, A. 1978. S o u r c e m e c h a n i s m o f t h e 1906 San Francisco earthquake. P h y s i c s of t h e E a r t h and P l a n e t a r y I n t e r i o r s , 17, p p . 163-181.  7.  Ben-Menahem, A., a n d T o k s o z , N. M. 1962. S o u r c e m e c h a n i s m f r o m s p e c t r a o f l o n g - p e r i o d s e i s m i c w a v e s , 1: The M o n g o l i a n e a r t h q u a k e o f December 4, 1957. J o u r n a l o f G e o p h y s i c a l R e s e a r c h , 67, pp. 1943-1955.  8.  Ben-Menahem, A., a n d T o k s o z , M. N. 1963a. Sourcem e c h a n i s m f r o m s p e c t r a o f l o n g - p e r i o d s e i s m i c w a v e s , 2: The K a m c h a t k a e a r t h q u a k e o f November 4, 1952. J o u r n a l o f G e o p h y s i c a l R e s e a r c h , 68, pp. 5207-5222.  9.  Ben-Menahem, A., a n d T o k s o z , M. N. 1963b. Sourcem e c h a n i s m f r o m s p e c t r a o f l o n g - p e r i o d s u r f a c e w a v e s , 3: The A l a s k a e a r t h q u a k e o f J u l y 10, 1958. B u l l e t i n o f t h e S e i s m o l o g i c a l S o c i e t y of A m e r i c a , 53, pp. 905-919.  1980. Q u a n t i t a t i v e Freeman Co., San F r a n c i s c o ,  10.  C h a n d r a , U. 1974. S e i s m i c i t y , e a r t h q u a k e m e c h a n i s m s and t e c t o n i c s a l o n g t h e w e s t e r n c o a s t of N o r t h A m e r i c a , from 42° t o 61°N. B u l l e t i n o f t h e S e i s m o l o g i c a l S o c i e t y o f A m e r i c a , 64, pp. 1529-1549.  11.  C h a s e , C. G. 1978. P l a t e k i n e m a t i c s : The A m e r i c a s , E a s t A f r i c a and t h e r e s t of t h e w o r l d . E a r t h and P l a n e t a r y S c i e n c e L e t t e r s , 3 7 , pp. 355-368.>  1 02  12.  F o r s y t h , D. A., B e r r y , M. J . , and E l l i s , R. M. A r e f r a c t i o n survey across the Canadian C o r d i l l e r a 54°N. C a n a d i a n J o u r n a l o f E a r t h S c i e n c e s , 11, pp. 548.  13.  F u r u m o t o , M. 1979. I n i t i a l p h a s e a n a l y s i s o f R Waves from g r e a t e a r t h q u a k e s . J o u r n a l of G e o p h y s i c a l R e s e a r c h , 84, pp. 6867-6874.  14.  G e l l e r , J . , and K a n a m o r i , H. 1977. Magnitudes of great s h a l l o w e a r t h q u a k e s f r o m 1944 t o 1952. B u l l e t i n of t h e S e i s m o l o g i c a l S o c i e t y o f A m e r i c a , 67, pp. 587-598.  15.  H a r k r i d e r , D. G. 1970. S u r f a c e waves i n m u l t i l a y e r e d e l a s t i c media. 2. H i g h e r mode s p e c t r a and s p e c t r a l r a t i o s from p o i n t s o u r c e s i n p l a n e l a y e r e d e a r t h models. B u l l e t i n o f t h e S e i s m o l o g i c a l S o c i e t y o f A m e r i c a , 60, pp. 1937-1988.  16.  H a s k e l l , N. A. 1953. The d i s p e r s i o n o f s u r f a c e waves on m u l t i l a y e r e d media. B u l l e t i n of the S e i s m o l o g i c a l S o c i e t y of A m e r i c a , 4 3 , pp. 17-34.  17.  H e r r m a n n , R. B., e d . , 1978. Computer P r o g r a m s I n E a r t h q u a k e S e i s m o l o g y , Department of E a r t h and A t m o s p h e r i c Sciences, Saint Louis U n i v e r s i t y .  18.  H o d g s o n , J . H., and M i l n e , W. G. 1951. D i r e c t i o n of f a u l t i n g i n c e r t a i n e a r t h q u a k e s of the n o r t h P a c i f i c . B u l l e t i n o f t h e S e i s m o l o g i c a l S o c i e t y o f A m e r i c a , 4 1 , pp. 221-242.  19.  H o d g s o n , J . H., and S t o r e y , R. S. 1954. D i r e c t i o n of f a u l t i n g i n some o f t h e l a r g e r e a r t h q u a k e s o f 1949. B u l l e t i n o f t h e S e i s m o l o g i c a l S o c i e t y o f A m e r i c a , 44, pp. 57-83.  20.  H o r n , J . R., C l o w e s , R. M., E l l i s , R. M., a n d B i r d , N. 1984. The s e i s m i c s t r u c t u r e a c r o s s an a c t i v e o c e a n i c / c o n t i n e n t a l t r a n s f o r m f a u l t zone. J o u r n a l of G e o p h y s i c a l R e s e a r c h , 89, pp. 3107-3120.  21.  H o r n e r , R. B. 1983. S e i s m i c i t y i n the S t . E l i a s Region o f n o r t h w e s t e r n Canada and s o u t h e a s t e r n A l a s k a . Bulletin o f t h e S e i s m o l o g i c a l S o c i e t y o f A m e r i c a , 7 3 , pp. 11171 1 38.  22.  Hyndman, R. D., and E l l i s , R. M. 1981, Queen C h a r l o t t e F a u l t Zone: m i c r o e a r t h q u a k e s f r o m a t e m p o r a r y a r r a y o f l a n d s t a t i o n s and o c e a n b o t t o m s e i s m o g r a p h s . Canadian J o u r n a l o f E a r t h S c i e n c e s , 18, pp. 776-788.  23.  Hyndman, R. D., M., Chapman, D.  L e w i s , T. J . , Wright, J . S., and Yamano, M. 1982.  1974. at 533-  D.  A., B u r g e s s , Queen  1 03  C h a r l o t t e f a u l t zone: Heat f l o w measurements. Canadian J o u r n a l o f E a r t h S c i e n c e s , 19, p p . 1657-1669. 24.  Hyndman, R. D., a n d W e i c h e r t , D. H. 1983. S e i s m i c i t y and r a t e s o f r e l a t i v e m o t i o n o f p l a t e b o u n d a r i e s o f western North America. Geophysical J o u r n a l of the Royal A s t r o n o m i c a l S o c i e t y , 72, pp. 53-69.  25.  I i d a , K. 1965. E a r t h q u a k e m a g n i t u d e , e a r t h q u a k e f a u l t source dimensions. J o u r n a l o f E a r t h S c i e n c e o f Nagoya U n i v e r s i t y , 13, p p . 115-132.  26.  J e f f r e y s , H., a n d B u l l e n , K. E. 1967. S e i s m o l o g i c a l tables. B r i t i s h A s s o c i a t i o n f o r t h e Advancement o f S c i e n c e , Gray M i l n e T r u s t , O f f i c e of the B r i t i s h A s s o c i a t i o n , L o n d o n , 50 p p .  27.  K a n a m o r i , H. 1970. S y n t h e s i s o f l o n g - p e r i o d s u r f a c e waves a n d i t s a p p l i c a t i o n t o e a r t h q u a k e s o u r c e s t u d i e s K u r i l e I s l a n d s e a r t h q u a k e s o f O c t o b e r 13, 1963. J o u r n a l of G e o p h y s i c a l R e s e a r c h , 75, pp. 5011-5027.  28.  K a n a m o r i , H., a n d A n d e r s o n , D. L. 1975. T h e o r e t i c a l b a s i s o f some e m p i r i c a l r e l a t i o n s i n s e i s m o l o g y . Bulletin o f t h e S e i s m o l o g i c a l S o c i e t y o f A m e r i c a , 6 5 , p p . 10731095.  29.  K a s a h a r a , K. 1981. E a r t h q u a k e M e c h a n i c s , C a m b r i d g e U n i v e r s i t y P r e s s , C a m b r i d g e , UK., 284 p p .  30.  K e l l e h e r , J . A. 1972. R u p t u r e z o n e s o f l a r g e S o u t h A m e r i c a n e a r t h q u a k e s a n d some p r e d i c t i o n s . J o u r n a l o f G e o p h y s i c a l R e s e a r c h , 79, pp. 2087-2103.  31.  K e l l e h e r , J . , a n d S a v i n o , J . 1975. D i s t r i b u t i o n o f s e i s m i c i t y b e f o r e l a r g e s t r i k e - s l i p and t h r u s t type earthquakes. J o u r n a l of G e o p h y s i c a l R e s e a r c h , 80, pp.260271.  32.  K o v a c h , R. L. 1965. S e i s m i c s u r f a c e w a v e s : some o b s e r v a t i o n s and recent developments. P h y s i c s and C h e m i s t r y o f t h e E a r t h , 6, p p . 251-314.  33.  L a n g s t o n , C. A. 1978. The F e b r u a r y 9, 1971 San F e r n a n d o Earthquake: A study of source f i n i t e n e s s i n t e l e s e i s m i c body w a v e s . B u l l e t i n of the S e i s m o l o g i c a l S o c i e t y of A m e r i c a , 68, p p . 1.-29.  34.  L a t h r a m , E. H. 1964. A p p a r e n t r i g h t l a t e r a l s e p a r a t i o n of t h e Chatham S t r a i t f a u l t , s o u t h e a s t A l a s k a . Bulletin of t h e S e i s m o l o g i c a l S o c i e t y o f A m e r i c a , 75, pp. 249-252.  35.  M i n s t e r , J . B., a n d J o r d a n , T. H. 1978. P r e s e n t day plate motions. J o u r n a l o f G e o p h y s i c a l R e s e a r c h , 8 3 , pp.  104  5331-5354. 36.  P a g e , R. 1969. L a t e C e n o z o i c movement on t h e F a i r w e a t h e r fault i n southeastern Alaska. B u l l e t i n of the S e i s m o l o g i c a l S o c i e t y of A m e r i c a , 80, pp. 1873-1877.  37.  P e r e z , 0. J . , a n d J a c o b , K. H. 1980. T e c t o n i c m o d e l and s e i s m i c p o t e n t i a l o f t h e e a s t e r n G u l f o f A l a s k a a n d Yakataga s e i s m i c gap. J o u r n a l of G e o p h y s i c a l R e s e a r c h , 85, pp. 7132-7150.  38.  P r e s s , F., Ben-Menahem, A., a n d T o k s o z , N. M. 1961. E x p e r i m e n t a l d e t e r m i n a t i o n of earthquake f a u l t l e n g t h and rupture v e l o c i t y . J o u r n a l o f G e o p h y s i c a l R e s e a r c h , 66, pp. 3471-3485.  39.  R i c h t e r , C. F. 1958. E l e m e n t a r y S e i s m o l o g y . Freeman Co., San F r a n c i s c o , CA., p. 6 9 .  40.  R i d d i h o u g h , R. P. 1977. A m o d e l f o r r e c e n t p l a t e i n t e r a c t i o n s o f f Canada's west c o a s t . Canadian J o u r n a l of E a r t h S c i e n c e s , 14, pp. 384-396.  41.  R i d d i h o u g h , R. P., C u r r i e , R. G., a n d Hyndman, R. D. 1980. The D e l w o o d K n o l l s a n d t h e i r r o l e i n t r i p l e j u n c t i o n t e c t o n i c s o f f n o r t h e r n Vancouver I s l a n d . C a n a d i a n J o u r n a l o f E a r t h S c i e n c e s , 17, p p . 577-593.  42.  R o g e r s , G. 1976. A m i c r o e a r t h q u a k e s t u d y i n n o r t h w e s t B r i t i s h Columbia and s o u t h e a s t A l a s k a . B u l l e t i n of the S e i s m o l o g i c a l S o c i e t y of A m e r i c a , 66, pp. 1643-1655.  43.  R o g e r s , G. 1983. S e i s m o t e c t o n i c s o f B r i t i s h C o l u m b i a . Ph.D. t h e s i s , U n i v e r s i t y o f B r i t i s h C o l u m b i a , 247 p p .  44.  S t a u d e r , W. 1959. A m e c h a n i s m s t u d y : The e a r t h q u a k e o f O c t o b e r 2 4 , 1927. G e o f i s i c a P u r a e A p p l i c a t a , 44, p. 135.  45.  S t a u d e r , W. 1960. The A l a s k a e a r t h q u a k e o f J u l y 10, 1958: S e i s m i c s t u d i e s . B u l l e t i n of the S e i s m o l o g i c a l S o c i e t y o f A m e r i c a , 50, p p . 293-322.  46.  T o b i n , P. G., a n d S y k e s , L. R. 1968. S e i s m i c i t y a n d t e c t o n i c s of t h e n o r t h - e a s t P a c i f i c Ocean. Journal of G e o p h y s i c a l R e s e a r c h , 73, pp. 3821-3846.  47.  T o c h e r , D. 1958. E a r t h q u a k e e n e r g y a n d g r o u n d b r e a k a g e . B u l l e t i n o f t h e S e i s m o l o g i c a l S o c i e t y o f A m e r i c a , 48, p p . 147-152.  48.  T s a i , Y., a n d A k i , K. 1970. P r e c i s e f o c a l d e p t h d e t e r m i n a t i o n f r o m a m p l i t u d e s p e c t r a o f s u r f a c e waves. J o u r n a l of G e o p h y s i c a l R e s e a r c h , 75, pp. 5729-5741.  W.  H.  105  49.  Von Heune, R., S h o r , G., a n d Wageman, J . 1979. C o n t i n e n t a l margins of t h e e a s t e r n Gulf of A l a s k a and boundaries of t e c t o n i c p l a t e s . I n : G e o l o g i c a l and Geophysical I n v e s t i g a t i o n s of C o n t i n e n t a l Margins, e d i t e d by J . S. W a t k i n s , L. M o n t a d e n t , a n d P. W.  50.  W e t m i l l e r , R. J . , a n d H o r n e r , R. B. 1978. C a n a d i a n e a r t h q u a k e s 1976. S e i s m o l o g i c a l S e r i e s o f t h e E a r t h P h y s i c s B r a n c h , 7 9 , p. 7 5 .  51.  W i c k e n s , A. J . , a n d H o d g s o n , J . H. 1967. C o m p u t e r r e e v a l u a t i o n o f e a r t h q u a k e m e c h a n i s m s o l u t i o n s 1922-1962. P u b l i c a t i o n s of t h e Dominion O b s e r v a t o r y , Ottawa, 33, pp. 1-560.  52.  Wyss, M. 1978. E s t i m a t i n g maximum e x p e c t a b l e m a g n i t u d e of e a r t h q u a k e f r o m f a u l t l e n g t h ( a b s t r a c t ) . EOS, T r a n s a c t i o n s o f t h e A m e r i c a n G e o p h y s i c a l U n i o n , 5 9 , p. 1 125.  53.  Wyss, M. 1979. E s t i m a t i n g maximum e x p e c t a b l e m a g n i t u d e o f e a r t h q u a k e s f r o m f a u l t d i m e n s i o n s . G e o l o g y , 7, p p 3 3 6 340.  106  APPENDIX A - L I S T OF SEISMOGRAPH STATIONS Instruments  Type o f R e c o r d s Received Source  Berkeley (BRK) B e n i o f f NS,EW,Z photocopy Berkeley-Network Aug.22,23 a n d O c t . 3 1 - m e s s y t r a c e s , o f f s c a l e . (Berk-Net) Bermuda (BEC) M i l n e - S h a w NE,NW m i c r o f i l m World Data Center A A u g . 2 2 - o f f s c a l e , Aug.23-o.k., O c t . 3 1 - a m p l i t u e s t o o small.(WDC-A) .  B o u l d e r C i t y (BCN) No r e c o r d s r e c e i v e d  Benioff  NS,EW,Z  WDC-A  Bozeman (BOZ) McComb-Romberg N,E m i c r o f i l m A u g . 2 2 - o f f s c a l e , Aug.23 a n d O c t . 3 1 - a r e good.  WDC-A  Chicago no r e c o r d s  WDC-A  (CHK) received  McComb-Romberg N,E  College (COL) B e n i o f f N,E Aug.22,23 a n d O c t . 3 1 - a l l o f f s c a l e . Columbia no r e c o r d s  (CSC) received  McComb-Romberg N,E  De B i l t (DBN) G a l i t z i n Z,N,E Aug.22,23 a n d O c t . 3 1 - a l l e x c e l l e n t .  .... microfilm ....  WDC-A WDC-A  photocopy  Fresno (FRE) S p r e n g n e t h e r Z,N,E p h o t o c o p y Aug.23 o n l y - e x c e l l e n t .  De B i l t Berk-Net  Halifax (HAL) B o s c h - O m o r i N.,E o r i g i n a l Canadian-Network Aug.22-L2,R2 a m p l i t u d e s t o o s m a l l , A u g . 2 3 - g o o d , O c t . 3 1 - p o o r . ( C a n - N e t ) Honolulu (HON) M i l n e - S h a w N,E Aug.22,23 a n d O c t . 3 1 - g o o d .  microfilm  WDC-A  Melbourne (MEL) Milne-Shaw E photocopy Melbourne Aug.22-L2,R2 a m p l i t u d e s t o s m a l l , A u g . 2 3 - m i s s i n g , O c t . 3 1 - o . k . Mt. H a m i l t o n (MHC) Wood-Anderson N,E, B e n i o f f i n s t r u m e n t t o o s h o r t p e r i o d t o be u s e f u l .  Z  microfilm Berk-Net  Ottawa (OTT) M i l n e - S h a w N,E, B e n i o f f z o r i g i n a l Can-Net Aug;22-L2,R2 a m p l i t u d e s t o o s m a l l , Aug.23 a n d O c t . 3 1 - g o o d . Pasadena (PAS) B e n i o f f Z,N,E Aug.22,23 a n d O c t . 3 l - a l l good.  microfilm  Pasadena  Perth (PER) Milne-Shaw N Aug.22 o n l y - u n r e a d a b l e  photocopy  Perth  Philadelphia  (PHI)  Wenner N,E  WDC-A  1 07  No  records  received  P i e r c e F e r r y (PFA) No r e c o r d s r e c e i v e d  Benioff  Z,N,E  ....  WDC-A  Rapid C i t y (RCD) Wood-Anderson E microfilm i n s t r u m e n t t o o s h o r t p e r i o d t o be u s e f u l .  WDC-A  Riverview (RIV) G a l i t z i n Z,N,E photocopy Riverview A u g . 2 2 - o f f s c a l e , Aug.23 a n d O c t . 3 1 - c o n f u s e d t i m i n g , r e c o r d s s u s p e c r S a l t L a k e C i t y (SLC) Bosh-Omori-McComb-Romberg N,E m i c r o f i l m Aug.22,23-off s c a l e , Oct.3l-good. WDC-A Saskatoon (SAS) Oct.31 only-o.k.  M i l n e - S h a w NE,NW  original  San J u a n (SJP) Wenner N,E microfilm A u g . 2 2 - o f f s c a l e , Aug.23 a n d O c t . 3 1 - g o o d .  Can-Net WDC-A  Seven F a l l s (SFA) Milne-Shaw E original Can-Net Aug.22-L2,R2 a m p l i t u d e s t o o s m a l l , Aug.23 a n d O c t . 3 1 - o . k . Shasta No r e c o r d s  (SHS) received  Benioff  Z,N,E  WDC-A  S h a w i n g a n F a l l s (SHF) Wood-Anderson N original Can-Net Aug.22-L2,R2 a m p l i t u d e s t o o s m a l l , Aug.23 a n d O c t . 3 1 - o . k . Sitka (SIT) Wenner N,E Aug.22,23 a n d O c t . 3 1 - a l l o f f s c a l e .  original  Stuttgart (STU) G a l i t z i n - W i l i p Z,N,E R e c e i v e d a r e p l y , b u t r e f u s e d t o send r e c o r d s . Tokyo (TOK) No r e s p o n s e .  W i e c h e r t , Omori, G a l i t z i n  Sitka Stuttgart  .... T o k y o  Tucson (TUO) Wood-Anderson NS,EW, B e n i o f f LPZ m i c r o f i l m A u g . 2 2 , 2 3 - o . k . , O c t . 3 1 - r i p s i n r e c o r d s make t h i s u s e l e s s , Uppsala (UPP) W i e c h e r t N,E photocopy Uppsala Aug.22-L2,R2 a m p l i t u d e s t o o s m a l l , A u g . 2 3 a n d O c t . 3 1 - a m p . t o o Utsunomiya (UTS) No r e s p o n s e Victoria instrument  Wiechert  Z,N,E  ....  (VIC) Benioff Z original t o o s h o r t p e r i o d t o be u s e f u l .  small  Utsunomiya Can-Net  108  APPENDIX B ~ WORLD AVERAGED PHASE V E L O C I T I E S AND Q VALUES LOVE PHASE V E L O C I T I E S PERIOD ( s ) 48. 86.24 90.55 100.61 113.16 129.26 143.54 161.35 180.52 196.05 209.57 230.79 249.79 256.84 264.31 299.19  C  Q VALUES  (km/s)  4.49 4.616 4.626 4.651 4.693 4.725 4.764 4.815 4.871 4.917 4.959 5.025 5.085 5. 107 5.131 5.244  (1) (1) (1) (1) (1) (1) (1) (1) (1) (1) (1) (1) (1) (1) (1) (1)  PERIOD ( s ) Q 44.68 53.94 72.36 102.59 125.92 139.46 161.78 181.04 200.95 210.21 225.70 250.66 281.55 300.37  1 97 187 190 139 1 19 11 6 121 119 11 1 11 1 11 3 11 2 11 5 1 10  U  (km/s)  5.519 5.265 5.413 4.498 4.385 4.385 4.384 4.382 4.382 4.382 4.382 4.386 4.397 4.407  \) xio k 6.46 5.91 4.22 4.89 4.78 4.42 3.66 3.32 3.21 3.07 2.81 2.55 2.20 2.15  (2 <2 (2 (2 < 1 11 < 1 <1 (1 I; 1 < I; 1 < 1 I; 1 L  RAYLEIGH PHASE V E L O C I T I E S PERIOD ( s ) C 10.0 20.0 25.0 30.0 35.0 40.0 46.0 92.0 125.0 1 50.0 1 75.0 200.0 225.0 250.0 275.0 300.0  Q VALUES  (km/s)  3.39 3.62 3.53 3.85 3.90 3.93 4.0 4.083 4. 196 4.296 4.432 4.575 4.739 4.918 5. 1 06 5.292  (3) (3) (3) (3) (4) (4) (4) (4) (1 ) (1 ) (1 ) (1 ) (1 ) (1) (1 ) (1)  PERIOD ( s ) Q 10.0 12.0 14.0 16.0 18.0 20.0 30.0 40.0 50.0 61 .08 73.92 97.73 125.04 160. 1 1 181.16 2.00.90 212.35 225.17 250.29 282.21 306.20  134 1 12 1 18 127 131 136 154 159 167 180 203 219  U (km/s) Vxio  3.837 3.812 3.758 3.707 3.649 3.615 3.588 3.577 3.569 3.578 3.652 3.758  33.0 30.0 26.0 23.0 20.0 16.0 13.0 10.0 10.0 10.0 9.13 7.24 5.33 4. 10 3.52 2.83 2.60 2.34 1 .94 1 .50 1 .24  5~  (5) (5) (5) (5) (5) (5) (5) (5) (5) (2) (2) (2) (6) (6) (6) (6) (6) (6) (6) (6) (6)  109  The  number i n t h e p a r e n t h e s i s  v a l u e s were t a k e n  from.  (1)  1970.  K a n a m o r i , H.  i n d i c a t e s the  V e l o c i t y and  P h y s i c s of t h e E a r t h and  Q values  source  that  the  of m a n t l e waves.  Planetary Interiors,  2, pp.  259-  275.  (2)  Dzienwonski,  A.  M.,  and  Anderson, D  .L.  1981.  Preliminary  r e f e r e n c e E a r t h m o d e l . P h y s i c s of t h e E a r t h and Interiors,  (3)  (4)  A k i , K.,  and  Vol.  W.  1.  K o v a c h , R. and  R i c h a r d s , P. G. H.  L.  pp.  H e r r m a n n , R. In:  Freman Co.,  1965,  1980.  Q u a n t i t a t i v e Seismology,  p.284.  Seismic  s u r f a c e w a v e s : Some Chemistry  observations of  B.,  ed.,  1978.  Input  t o the computer program  Computer p r o g r a m s i n e a r t h q u a k e s e i s m o l o g y ,  S a i n t L o u i s U n i v e r s i t y , pp.  C h a e l , E.  P.,  and  2,  A n d e r s o n , D.  L.  1982.  (XI -1 5) - (XI--28)  Global Q  f r o m a n t i p o d a l R a y l e i g h w a v e s , J o u r n a l of pp.  Vol.  Atmospheric  Sciences,  R e s e a r c h , 87,  the  251-314.  D e p t . o f E a r t h and  (6)  297-356.  r e c e n t d e v e l o p m e n t s , P h y s i c s and  E a r t h , 6,  (5)  25, pp.  Planetary  2840-2850.  estimates  Geophysical  QU  1 10  APPENDIX C - EARTH MODEL USED FOR THE AUGUST 23 AND OCTOBER 31 MECHANISM SOLUTIONS The  f o l l o w i n g model was u s e d a s t h e e a r t h m o d e l i n  determining  the t h e o r e t i c a l surface  Continental  wave r a d i a t i o n  U.S.A.  C r u s t a l and U p p e r  Mantle S t r u c t u r e  H km  P  a  km/s  28.0 12.0 13.0 25.0 50.0 75.0 50.0  6.15 6.70 7.96 7.85 7.85 7.85 8.20 8.40  km/s 3.55 3.80 4.60 4.50 4.41 4.41 4.50 4.60  Springer-Verlag  (H=layer t h i c k n e s s ) .  P g/cm  M,10" dyne/cnf  X 10" dyne/cm  2.74 3.00 3.37 3.39 3.42 3.45 3.47 3.50  3.453 4.332 7.131 6.864 6.651 6.710 7.027 7.406  3.457 4.803 7.091 7.161 7.772 7.841 9.279 9.884  (From Ben-Menahem, A., a n d S i n g h , S. and S o u r c e s .  pattern.  Co., p p .  J.  1981.  316.)  f  Seismic  1  Waves  APPENDIX D - INSTRUMENT RESPONSE niRVF.c  DBN N S . E W IOOOT  1000^3  TS:25  S  TG:25 S V:290 \00-d  o  lOOd  H I—  <x  cn  UOd  <10  LD cn  CC 51  I  10 PERJ0D  100  •H  '000  I  • I • "'I  I  GALITIZIN  DBN  1  I ' I ""I >—| ' | "") 10 100 PERIOD  1—)  i | 11ri]  1000  I .1  i  IiI  11 i i |  1  1—i  I 111 i i |  1—i  i  10 PERIOD  BOSCH-OMORI S L T  i  i •  I>i  100  1—i  i 11 rrt]  1000  BOSCH-OMORI H A L  MRGNIFICRTION  —  en  o  -  c  §  °  *  X  m  2  ¥ 5°  o  III  IIIIL  MAGNIFICATION 5 '  o o o  -  8  ' ' I mil  |  J—'  '  m  > oo  <  o  o  «  2  ro ro m 8^  o  —I  I  I  I mil  MAGNIFICATION 5  —I—  1 1 ,  •  I  1  o o o  -  8  I I 1111  I  I nu)  0)  m o z m H X m 30  cd  33 _ O  O u H  O'  o  <  ••  CD  ••  ro roW  o o  8^  o  SIT  ro m B  /  N  

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.831.1-0052501/manifest

Comment

Related Items