UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Crustal structure from a seismic refraction profile across southern British Columbia Cumming, William B. 1977

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-UBC_1977_A6_7 C84.pdf [ 4.06MB ]
Metadata
JSON: 831-1.0052994.json
JSON-LD: 831-1.0052994-ld.json
RDF/XML (Pretty): 831-1.0052994-rdf.xml
RDF/JSON: 831-1.0052994-rdf.json
Turtle: 831-1.0052994-turtle.txt
N-Triples: 831-1.0052994-rdf-ntriples.txt
Original Record: 831-1.0052994-source.json
Full Text
831-1.0052994-fulltext.txt
Citation
831-1.0052994.ris

Full Text

CRUSTAL STRUCTURE FROM A PROFILE ACROSS SOUTHERN SEISMIC BRITISH REFRACTION COLUMBIA Wil l i a m B. Cumming B. S c . , U n i v e r s i t y of Toronto,1974 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the Department of Geophysics and Astronomy We accept t h i s t h e s i s as conforming to the r e q u i r e d standard The U n i v e r s i t y of B r i t i s h Columbia March,1977 fc) William B. Chiming In presenting th is thes is in p a r t i a l fu l f i lment of the requirements for an advanced degree at the Un ivers i ty of B r i t i s h Columbia, I agree that the L ibrary shal l make it f ree ly ava i lab le for reference and study. I fur ther agree that permission for extensive copying of th is thes is for scho la r ly purposes may be granted by the Head of my Department or by his representat ives . It is understood that copying or pub l ica t ion of th is thes is for f inanc ia l gain sha l l not be allowed without my wri t ten permission. Department of C^Co^/vyf/'cS <?>-, &( /A"^T>r^m0 The Univers i ty of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 Date i ftBSTBACT A p a r t i a l l y r e v ersed s e i s m i c r e f r a c t i o n p r o f i l e u t i l i z i n g mine b l a s t s as so u r c e s was recorded a c r o s s southern B r i t i s h Columbia from Sparwood t o the Highland V a l l e y . The westwardly d i r e c t e d p r o f i l e c o n s i s t e d of 32 short p e r i o d seismograms c o v e r i n g 440 km, while the r e v e r s e d l i n e extended 330 km with 41 seismograms. The FM f i e l d tapes were d i g i t i z e d , f i l t e r e d , and combined i n t o v e r t i c a l component r e c o r d s e c t i o n s . Instrument and shot amplitude c o r r e c t i o n s were a p p l i e d i n order t o d i s p l a y the t r u e r e l a t i v e amplitude v a r i a t i o n along the p r o f i l e . As w e l l as ge o m e t r i c a l t e c h n i g u e s , l e a s t sguares delay-time methods and d i s c ray theory s y n t h e t i c seismograms were used to i n t e r p r e t the data. Where the p r o f i l e c r o s s e s the Eocky Mountain Trench and the Okanagan V a l l e y , the s e i s m i c data show a r r i v a l time and amplitude anomalies i n the approximately 6.0 km/s upper c r u s t a l r e f r a c t i o n a r r i v a l s . An i n t e r m e d i a t e c r u s t a l l a y e r of v e l o c i t y 7.05 km/s, depth 29 km, and t h i c k n e s s 9 km i s de f i n e d by second a r r i v a l data recorded 100 to 200 km west of the K a i s e r shot p o i n t . There i s poorer evidence, based on data between 80 and 180 km from the Highland V a l l e y shot p o i n t , f o r a l a y e r with a v e l o c i t y of 7.35 km/s, a depth of 15 to 24 km, and a t h i c k n e s s of 6 t o 10 km. The M-i i d i s c o n t i n u i t y g e n e r a l l y d i p s to the e a s t from an approximate depth of 33 km near the Highland V a l l e y , to about 42 km j u s t t o the west of the K a i s e r shot p o i n t . The upper mantle v e l o c i t y i s 7.8 km/s between the Okanagan V a l l e y and Kootenay Lake. Delay time i n t e r p r e t a t i o n s suggest t h a t a 165 km wavelength anomaly i n average c r u s t a l v e l o c i t y and/or depth t o the mantle occurs i n the E a s t e r n Metamorphic B e l t . . The anomaly i s probably a s s o c i a t e d with a deep t r a n s i t i o n zone between the Arrow Lakes and Kootenay Lake. The r e s u l t s of the present study are a p p l i c a b l e p r i m a r i l y t o the e a s t e r n I n t e r i o r Plateaux and the E a s t e r n Metamorphic B e l t south of 51°N. i i i l i J I J CF CONTENTS AESTRACT . i TAELE CF CONTENTS . i i i LIST CF TABLES i v LIST CF FIGURES V ACKNOWLEDGEMENTS v i C HAFT EE I 1 1. A c t i v a t i o n ....................................... 1 2. E e g i o n a l Geology . . . . 4 3. G e o p h y s i c a l Review .........10 CHAPTER I I . 16 1. Data A g u i s i t i o n ......16 2. P r e l i m i n a r y A n a l y s i s 25 CHAPTER I I I . 35 1. P r e l i m i n a r y I n t e r p r e t a t i o n 35 2. Near Source C r u s t a l P r o f i l e from Highland V a l l e y . 4 1 3. Near Source C r u s t a l F r c f i l e frcm K a i s e r 4 7 4 . S y n t h e t i c Seismcgrams .....52 5. l e a s t - S g u a r e s Delay Times ........................ 6 4 6. l i s c u s s i o n ......72 7 . C o n c l u s i o n s 7 7 LIST CF REFERENCES 7 9 i v IIST CF TABLES Table 1. Shot S t a t i s t i c s 18 Table 2a. K a i s e r S t a t i o n S t a t i s t i c s ........21 Table 2b. Highland V a l l e y S t a t i o n S t a t i s t i c s 23 V LIST CF FIGURES Fi g u r e 1. G e o l o g i c a l and S t a t i o n L o c a t i o n Raps .......3 Figu r e 2. K a i s e r Record S e c t i o n 29 Fi g u r e 3. Highland V a l l e y Record S e c t i o n 31 Fi g u r e 4. Near Source Highland V a l l e y S e c t i o n ........ 33 Fi g u r e 5. T r a v e l Tiroes, Topography, And Geology 37 Figu r e 6. Near Source Highland V a l l e y S e c t i o n with T r a v e l Time Curves 42 Figure 7. Schematic of Near Source K a i s e r Seistnic S t r u c t u r e 50 Fi g u r e 8. K a i s e r S e c t i o n With T r a v e l Time Curves .....54 Figu r e 9. S y n t h e t i c Seismogram S e c t i o n And V e l o c i t y Model of K a i s e r P r o f i l e ..56 Fi g u r e 10. Highland V a l l e y S e c t i o n with T r a v e l Time Curves 59 Figu r e 11. S y n t h e t i c seismogram s e c t i o n And V e l o c i t y Model of Highland V a l l e y P r o f i l e 61 F i g u r e 12a. Delay Time S o l u t i o n For A Plane 66 F i g u r e 12b. Delay Time S o l u t i o n With One F o u r i e r Term 68 ACKNOWLEDGEMENTS The guidance and a s s i s t a n c e of my s u p e r v i s o r . Dr.R.M. Clowes, has been g r e a t l y a p p r e c i a t e d . Dr. R.M. E l l i s who read the manuscript and provided f i e l d a s s i s t a n c e a l s o deserves thanks. The t e c h n i c a l p r e p a r a t i o n and companionable f i e l d work of C h r i s West, and the t e c h n i c a l c l a r i f i c a t i o n s by Ecb Meldrum were much a p p r e c i a t e d . Messrs. Peter S u l e , Bob C l a y t o n , George Spence, B a s i l P e t e r s , Stan Knize and Steven Malecek provided e n t h u s i a s t i c f i e l d a s s i s t a n c e . The personnel and management of Ka i s e r Resources, Bethlehem Copper, and Lornex Mining companies deserve s p e c i a l acknowledgement f o r t h e i r c o o p e r a t i o n a t the b l a s t s i t e and with shot data. The personnel of Cominco L t d . are a l s o thanked f o r t h e i r help i n the f i e l d and m a t e r i a l a s s i s t a n c e . The use of the s y n n t h e t i c seismogram programs of Dr. R.A. Wiggins was much a p p r e c i a t e d . The time-term programs provided by C.A.G. Fors y t h of the Earth P h y s i c s Eranch and modified by the author were a p p r e c i a t e d . Dr. L a r r y L i n e s , George McMechan, Tim Ahern, Rob C l a y t o n , John C. Davies, George Spence, Stevs Malecek, and Mat Y e d l i n provided programming a s s i s t a n c e and s u g g e s t i o n s . The authors understanding of the geology of the Canadian C o r d i l l e r a was c l a r i f i e d i n d i s c u s s i o n s with Dr. R. Armstrong, Ian Hunt, and Dr. C. Godwin of the Department o f G e o l o g i c a l S c i e n c e s a t the D n i v e r s i t y of B r i t i s h Columbia, and Er. G. Eisbacher of the G e o l o g i c a l Survey of Canada. S p e c i a l a p p r e c i a t i o n i s due my wife Yasmin, whc keypunched the d r a f t s and encouraged a healthy academic p e r s p e c t i v e . T h i s p r o j e c t was supported by the N a t i o n a l Research C o u n c i l cf Canada, the Department of Energy, Mines and Resources of Canada, and the B r i t i s h Columbia Department Mines and Fatroleum Resources. 1 1. M o t i v a t i o n A r e v e r s e d s e i s m i c r e f r a c t i o n p r o f i l e between t h e K a i s e r Resources s t r i p c o a l mine near Sparwcod, B r i t i s h C o l u m b i a , and the Lornex and Bethlehem open p i t copper mines i n t h e H i g h l a n d V a l l e y , was begun i n 1973. I t i s a c o n t i n u a t i o n o f the U n i v e r s i t y of B r i t i s h C olumbia's s e i s m i c s t r u c t u r a l s t u d i e s i n the Canadian C o r d i l l e r a u t i l i z i n g mine b l a s t s as energy s o u r c e s . T h i s work e x t e n d s s e i s m i c coverage t o the west c f an e a r l i e r s t u d y which used the K a i s e r shot p c i n t f o r a n o r t h w e s t e r l y p r o f i l e a l o n g the Rocky Mountain Trench (Bennett et a l . , 1 9 7 5 ) . The p r o f i l e o f the p r e s e n t s t u d y c r o s s e s o u t s t a n d i n g g e o l o g i c a l f e a t u r e s t h a t are p o o r l y u n d e r s t o o d , e s p e c i a l l y a t d e p t h . Any deep e x p r e s s i o n o f s u r f a c e v a r i a b i l i t y may be e c o n o m i c a l l y i m p o r t a n t i n e x p l a i n i n g the f o r m a t i o n o f major m i n e r a l d e p o s i t s . For example, Cominco's S u l l i v a n ore body has been r e l a t e d t o a F r e c a m b r i a n r i f t (Kanasewich,1969) and i t i s e x a c t l y i n l i n e w i t h t h e p r o f i l e . However, p r e v i o u s g e o p h y s i c a l models of the upper mantle and c r u s t a c r o s s t h i s r e g i o n , based ma i n l y on g r a v i t y e v i d e n c e , have had very 2 l i t t l e c o r r o b o r a t i n g s e i s m i c data. The c o o p e r a t i o n of the mining companies i n o b t a i n i n g shot s t a t i s t i c s o f f e r e d a r e l a t i v e l y i n e x p e n s i v e o p p o r t u n i t y to u t i l i z e the e x c e p t i o n a l l y l a r g e shots i n a s e i s m i c i n v e s t i g a t i o n of a p o o r l y understood r e g i o n , 2. Regional Geology. The narrow r e g i o n of southern E r i t i s h Columbia w i t h i n which the p r o f i l e i s l o c a t e d c r e s s e s s e v e r a l g e o l o g i c a l zones (Figure 1 ) . At the e a s t e r n end, the K a i s e r shot p o i n t i s i n the Rocky Mountains. T h i s area was once a s t a b l e p l a t f o r m of Hudsonian s h i e l d - t y p e recks o v e r l a i n by m i o g e o c l i n a l sedimentary seguences. In s e v e r a l p u l s e s of a c t i v i t y , the f i r s t beginning i n the Mesozoic, and the most rec e n t ending i n the Eocene, a s e r i e s of low angle t h r u s t sheets have been stacked p r o g r e s s i v e l y eastward. There i s g e n e r a l agreement t h a t , i n the easternmost Front Ranges, a decollement s e p a r a t e s the l a r g e l y p a s s i v e c r y s t a l l i n e basement from the o v e r t h r u s t sediments. However, c o n s i d e r a b l e debate has a r i s e n over the degree of basement involvement i n the t h r u s t i n g i n the Main and Western Ranges of the Rocky Mountains. The l a t e r a l s h o r t e n i n g of the sedimentary s e c t i o n i s p a r t i a l l y c o n t r o l l e d by basement defo r m a t i o n , and the degree of s h o r t e n i n g w i l l c o n s t r a i n the minimum westerly d i s t a n c e of the P r c t e r o z o i c c o n t i n e n t a l s h e l f - s l o p e boundary from the present western margin of the Figure 1. G e o l o g i c a l and s t a t i o n l o c a t i o n maps. Upper map: The r e g i o n a l i z e d g e o l o g i c a l zone map i s modified from Stacey (1973). The area of the lower map i s o u t l i n e d with heavy l i n e s . Lower map: The open and c l o s e d c i r c l e s r epresent Highland V a l l e y and Kaiser r e c o r d i n g s i t e s r e s p e c t i v e l y . Alpha-numeric i d e n t i f i c a t i o n of r e c o r d i n g s i t e s i s e x p l a i n e d i n the t e x t . PNT i s the l o c a t i o n of the Canadian Standard Seismic Network s t a t i o n which was used f o r amplitude n o r m a l i z a t i o n . INTERIOR PLAINS 5 Pocky Mountains. Campbell (1973) suggests t h a t , t o the north of l a t i t u d e 55° at l e a s t , the basement has been deformed i n the Main Ranges,in the Western Ranges, and i n a l l of the mountains to the west of the Rocky Mountain Trench. A deccllement would f i t h i s i n t e r p r e t a t i o n o n l y i n the f r o n t Ranges and the F o o t h i l l s . However, the i n t e r p r e t a t i o n s of B a l l y et a l . (1966) and P r i c e and Mountjoy (1970) are s t i l l widely accepted. They extend the decollement w e l l to the west cf the Rocky Mountains, i n t o the E a s t e r n Metamorphic B e l t , T h i s i m p l i e s t h a t as much as 200 km of s h o r t e n i n g o c c u r r e d i n the t h r u s t zone, which would place, the . o r i g i n a l s h e l f slope assemblage west of the present day Arrow Lake. Campbell and E i s t a c h e r (personal communication, 1977) suggest t h a t the s h o r t e n i n g i s l e s s than h a l f of t h i s amount. The Western Ranges are terminated to the north cf the' area of t h i s study, while the Main Ranges are p h y s i o g r a p h i c a l l y t r u n c a t e d along a l i n e approximately c o i n c i d e n t with the p r o f i l e , T h e r e f o r e , i t would be d i f f i c u l t to use the i n f o r m a t i o n from t h i s study t o r e s o l v e these models of the Reeky Mountains. The Rocky Mountain Trench i s an intermontane v a l l e y extending over 1600 km from Montana t o northern B r i t i s h Columbia. I t forms a sharp p h y s i o g r a p h i c and g e o l o g i c boundary between the g e n e r a l l y i m b r i c a t e s t r u c t u r e cf the Rocky Mountains to the n o r t h e a s t , and the more complex s t r u c t u r e of the v a r i o u s ranges to the southwest. The P u r c e l l Mountains are bounded by the t r e n c h at the l a t i t u d e s 6 of t h i s study. However, f a r t h e r n o r t h , the t r e n c h t r u n c a t e s a s e r i e s of ranges i n the E a s t e r n Metamorphic B e l t i n an "en e c h e l c n " f a s h i o n . The Rocky Mountain Trench has been a very enigmatic s t r u c t u r e . In Montana i t appears to be a gracen, while i n the north i t has been i n t e r p r e t e d by d i f f e r e n t authors as a h a l f - g r a t e n , a t r a n s c u r r e n t f a u l t , a t h r u s t f a u l t s t r u c t u r e , or a p u r e l y e r o s i o n a l f e a t u r e . The l i n e a r i t y and p e r s i s t e n c e of the t r e n c h makes the l a s t u n l i k e l y . S p e c u l a t i o n as t o the o r i g i n of the trench f r e g u e n t l y r e f l e c t s Leech's (1965) suggestion t h a t , "the t r e n c h may mark an o l d , deep f r a c t u r e zone that has r e a s s e r t e d i t s e l f through the a l l o c t h o n o u s veneer." However, the complexity of the geology makes even a r e c o n s t r u c t i o n of the "veneer" d i f f i c u l t . Any u n d e r l y i n g v e s t i g i a l t e c t o n i c f e a t u r e may be d e t e c t a b l e only by i n f e r e n c e . More i m p o r t a n t l y , the p r o x i m i t y of such a boundary may be very i n d i r e c t l y r e l a t e d t o the p h y s i o g r a p h i c t r e n c h , and i t may be c n l y c o i n c i d e n c e . Although the g e o l o g i c a l f o r m a t i o n s along the t r e n c h vary i n s t r u c t u r a l d e t a i l , they do seem to be c o n s i s t e n t with the e x t e n s i o n a l t e c t o n i c s t h a t have c h a r a c t e r i z e d t h i s part of the e a s t e r n C o r d i l l e r a s i n c e the Miocene, T h e r e f o r e , the p r e f e r r e d i n t e r p r e t a t i o n i s of a r e c e n t e x t e n s i o n a l f e a t u r e e x p r e s s i n g a l a t e - M e s o z o i c to Eocene boundary between the b r i t t l e and d u c t i l e deformation to the east and west r e s p e c t i v e l y . Deep s t r u c t u r e s may be i n d i r e c t l y i n v o l v e d . The P u r c e l l A n t i c l i n o r i u m i s a t h i c k sedimentary wedge 7 s e p a r a t i n g the E a s t e r n Metamorphic E e l t from the Rocky Mountain Trench i n southern B r i t i s h Columbia. As a s i m p l i f i c a t i o n , i t i s o f t e n i n c l u d e d i n the E a s t e r n Metamorphic B e l t as another t r u n c a t e d range (Wheeler and G a b r i e l s e , 1 9 7 2 ) . The sediments of the P u r c e l l s are g e n e r a l l y c h a r a c t e r i z e d as a c o n t i n e n t a l s l o p e assemblage, with the deeper water sediments i n the west grading to shallow water d e p o s i t s i n the more e a s t e r l y s e c t i o n s . The P r o t e r c z o i c P u r c e l l Group experienced mild deformation i n the Racklan orogeny from 1000 to 800 mya, probably a l s o i n v o l v i n g the c r y s t a l l i n e basement cn which i t was d e p o s i t e d . Unccmformably o v e r l a i n by the Windermere Group and P a l e o z o i c r o c k s , the e n t i r e sedimentary s e c t i o n was then f o l d e d , t h r u s t e d , i n t r u d e d , and m i l d l y metamorphosed du r i n g a s e r i e s of phases i n the Mesozoic. Despite the models of decollement s t r u c t u r e s ( B a l l y et a l . , 1966),the basement i n t h i s area was almost c e r t a i n l y i n v o l v e d i n the deformation. The E a s t e r n Metamorphic B e l t , which forms the c e n t r a l r e g i o n a c r o s s which the p r o f i l e was run, i s d i s t i n g u i s h e d from the P u r c e l l s by i t s high degree of metamorphism and widespread g r a n i t i c i n t r u s i o n . T h i s a r e a , o f t e n c a l l e d the Omenica C r y s t a l l i n e B e l t , i s dominated, p a r t i c u l a r l y i n i t s southwestern s e c t i o n s , by the Shuswap Complex of i n t e n s e l y a l t e r e d and deformed v o l c a n i c , sedimentary, and, perhaps, basement r o c k s . The r e g i o n i s u s u a l l y r e f e r r e d to as the "core zone" of the l a t e - M e s o z o i c deformation. The thermal a c t i v i t y appears to have occu r r e d mainly i n the J u r r a s i c , 8 f o l l o w e d by a milder T e r t i a r y event. Because of the i n t e n s e metamorphism, the s u b s t r u c t u r e of t h i s zone has o n l y r e c e n t l y become b e t t e r understood. Of p a r t i c u l a r i n t e r e s t i s a b e l t of g r a n i t o i d g n e i s s e s , approximately c o i n c i d e n t with Arrow Lake, t h a t a p p a r e n t l y r e p r e s e n t r e m o f c i l i z s d Hudsonian c r y s t a l l i n e basement (Wanless and Eessor, 1974). These rocks are probably not a simple e x t e n s i o n of the s h i e l d - t y p e rocks beneath the Rocky Mountains t h a t have been brought to the s u r f a c e . Duncan (personal communication,1977) has suggested t h a t a t e c t o n i c geometry with a major P a l e o z o i c t r a n s c u r r e n t (or transform) f a u l t along an Arrow l a k e " s u t u r e " zone b e t t e r agrees with the s t r u c t u r a l evidence than p r e v i o u s models i n v o l v i n g -eastward d i p p i n g subduction zones (Monger e t a l . , 1972). Although t h i s c o n s i d e r a b l y c o m p l i c a t e s the g e o l o g i c a l r e c o n s t r u c t i o n of t h i s r e g i o n , the f e a t u r e p r i m a r i l y c o n s i d e r e d i n the i n t e r p r e t a t i o n of the present study, i s the r e l a t i v e l y simple p a t t e r n of more i n t e n s e metamorphism i n the western s e c t i o n of the E a s t e r n Metamorphic B e l t . Another proposed t e c t o n i c " s u t u r e " zone, g e n e r a l l y along the Okanagan V a l l e y , separates the E a s t e r n Metamorphic E e l t from the I n t e r i o r Plateaux. The nature of t h i s " s u t u r e " i s i n c o n s i d e r a b l e doubt, although i t forms an obvious g e o l o g i c a l boundary. The I n t e r i o r Plateaux i s a heterogeneous, but r e l a t i v e l y undefcrmed group of v o l c a n i c , p l u t o n i c , and v o l c a n i c sedimentary rocks. These rocks are t y p i c a l of ocean b a s i n , i s l a n d a r c , and s u c c e s s o r b a s i n 9 s e t t i n g s . By a complex process of eastward d i p p i n g s u b d u c t i c n , seme obduction, and probably sotre t r a n s c u r r e n t movement, the rocks of the I n t e r i o r P l ateaux were brought i n t o t h e i r present p o s i t i o n r e l a t i v e to the E a s t e r n Metamorphic E e l t sometime d u r i n g the e a r l y Mesozoic (Monger et a l . , 1972). The r e a c t i v a t i o n of o l d f e a t u r e s i n d i f f e r e n t modes probably causes much of the c o n f u s i o n i n the i n t e r p r e t a t i o n of t h i s a r e a . Near the western margin of the I n t e r i o r P l a t e a u x , the Highland V a l l e y shot p c i n t s l i e around the core zone of the Mesozoic g r a n c d i o r i t e Guichcn Creek b a t h o l i t h which i n t r u d e s v o l c a n i c s and v o l c a n i c sediments. The gross s t r u c t u r e of the b a t h o l i t h has been determined from g r a v i t y data (Ager e t a l . , 1S73). I t appears to be a t i l t i n g f u n n e l shaped i n t r u s i o n . I t s v a r i o u s phases roughly encase each ether, with the most recent emplacement approximately i n the c e n t r e or "core zone" (Northcote, 1969). The disseminated copper m i n e r a l i z a t i o n i s a p p a r e n t l y a s s o c i a t e d with the core zene. In order to i n v e s t i g a t e the b a t h o l i t h , and the N i c o l a v o l c a n i c s on i t s e a s t e r n margin, a g r e a t e r d e n s i t y of r e c o r d i n g s i t e s was us€d near the Highland V a l l e y shot p c i n t s . 10 3• G e o p h y s i c a l Review The C o r d i l l e r a i n B r i t i s h Columbia has been the s u b j e c t c f c o n s i d e r a b l e g e o p h y s i c a l i n v e s t i g a t i o n much of which i s summarized i n Berry et a l . (1971). They pointed out that there are few mantle depth d a t e r m i n a t i o n s from s e i s m i c data i n the Eastern Metamorphic B e l t , although an average c r u s t a l t h i c k n e s s of 30 to 35 km was i m p l i e d by g r a v i t y data (Stacey, 1973 ) . Stacey developed a g r a v i t y model with a s l i g h t l y more dense mantle, and a l e s s dense c r u s t i n the c e n t r a l C o r d i l l e r a west of the Pocky Mountain Trench, than i n a d j a c e n t r e g i o n s . A vague mantle d e p t h - v e l o c i t y - d e n s i t y boundary based on the g r a v i t y data was suggested i n southern B r i t i s h Columbia running southwest to n o r t h e a s t . I t was placed between 49°N and 51°N. To the s c u t h , the M-d i s c o n t i n u i t y s l o p e d from 33 km i n the I n t e r i o r Plateaux to 45 km beneath the Rocky Mountains, and to the north the mantle dipped from 33 km to 53 km. A deep mantle between 50 and 60 km i n the northern Rocky Mountain Trench i s confirmed by Bennett et a l . ( 1 9 7 5 ) and Spence et a l . (1 977) . At the western end of the p r o f i l e of t h i s study, White et a l . (1968) found a t h r e e l a y e r c r u s t : a 5.2 km/s l a y e r over a 6.1 km/s c r u s t t h a t a p p a r e n t l y d i r e c t l y o v e r l i e s the mantle. A mantle d i s c o n t i n u i t y near 5 0° with an east-west s t r i k e was proposed. One mcdel had a v e l o c i t y change from 7.8 km/s i n the south to 8.1 km/s to the north i n a mantle 30 km deep. The a l t e r n a t e model had the mantle depth 11 changing from 33 km i n the north to 28 km i n the south, with a uniform Fn v e l o c i t y of 8.0 km/s. The nature of the cru s t - m a n t l e t r a n s i t i o n i n B r i t i s h Columbia has been s t u d i e d by Berry and F o r s y t h (1975), p r i m a r i l y i n the western C o r d i l l e r a , but with l i m i t e d data as f a r east as the Eastern Metamorphic E e l t . In the southwest,a mantle v e l o c i t y of 7.8 km/s i n c r e a s e s to 8.1 kir/s north of 51°, Time-term i n t e r p r e t a t i o n s r e v e a l a shallower upper mantle boundary i n the south, with a l e s s complex topography than p r o f i l e s north of 50° 30'N. Regional amplitude s t u d i e s suggest that the M - d i s c o n t i n u i t y becomes l e s s d i s t i n c t t o the southwest cf Kamloops, than to the northwest. Using s u r f a c e wave data, Wickens (1976) confirmed a tendency to a sharper c r u s t - m a n t l e t r a n s i t i o n t o the north and e a s t of the Highland V a l l e y shot p o i n t . A low v e l o c i t y l a y e r 40 to 50 km t h i c k and about 15 to 20 km beneath the «-d i s c o n t i n u i t y i n the I n t e r i o r P lateaux, was found t o become t h i c k e r and deeper t o the north and east. wickens a l s o confirmed the g e n e r a l l y low mantle v e l o c i t i e s p r e v i o u s l y suggested f o r the r e g i o n i n v e s t i g a t e d by the present study. A g e n e r a l s y n t h e s i s of pr e v i o u s s t u d i e s suggests t h a t a g e n t l y d i p p i n g upper mantle boundary , perhaps of v a r y i n g c h a r a c t e r l i e s along the p r o f i l e , with a v e l o c i t y of about 7.8 to 8.0 km/s and an average depth of 35 km. Although the upper c r u s t i s extremely complex at the s u r f a c e , i t i s reasonable to assume t h a t i t has r e l a t i v e l y 12 smooth a n o m a l i e s near mantle depths ( B e r r y and F c r s y t h , 1 975) . F a i r l y s i m p l e models have a c c o u n t e d f o r most of t h e c r u s t a l r e f r a c t i o n r e s u l t s , w i t h a 6.5 km/s average c r u s t west o f t h e I n t e r i o r P l a t e a u x g r a d i n g t o a 6.1 km/s average c r u s t i n the e a s t e r n C o r d i l l e r a . Wickens (1976) suggested t h a t t h e s e i s m i c r e f r a c t i o n e x p e r i m e n t s were unable to d e t e c t a c r u s t a l low v e l o c i t y zone t h a t was e v i d e n t f r c m s u r f a c e wave s t u d i e s . In the r e g i o n o f t h i s s t u d y , t h i s lew v e l o c i t y zone a p p a r e n t l y bottomed a t t h e M-d i s c o n t i n u i t y . A l t h o u g h such a f e a t u r e would te n d to g i v e a n omalously s h a l l o w M-depths from r e f r a c t i o n r e s u l t s , as Wickens p o i n t e d o u t , i t would be d i f f i c u l t t o d e t e c t w i t h r e f r a c t i o n d a t a . The c o r r e l a t i o n between the major g e o l o g i c a l d i v i s i o n s and magnetic a n o m a l i e s was d e s c r i b e d by Haines e t a l . ( 1 9 7 1 ) . The Rocky Mountain Trench forms t h e major magnetic boundary w i t h a s h a r p c o n t r a s t between t h e broad smooth a n o m a l i e s c h a r a c t e r i s t i c of t h e Canadian S h i e l d t o the e a s t , and the m a g n e t i c a l l y g u i e t E a s t e r n Metamorphic B e l t t o the west. The I n t e r i o r P l a t e a u x i s r e l a t i v e l y g u i e t w i t h p a t c h e s c f s m a l l s c a l e a n o m a l i e s . The Rocky Mountain Trench d i s c o n t i n u i t y has been e x t e n s i v e l y i n v e s t i g a t e d by Caner e t a l . (1971) u s i n g geomagnetic depth s c u n d i n g d a t a . The v e r t i c a l magnetic component, Z, has a marked d i s c o n t i n u i t y j u s t t o the west c f the t r e n c h , w i t h h i g h Z t o the e a s t , and low Z t o the west. T h i s f e a t u r e a p p a r e n t l y runs p a r a l l e l t o the t r e n c h frcm t h e n o r t h u n t i l i t r e a c h e s the n o r t h end of 13 the P u r c e l l A n t i c l i n o r i u m where i t f o l l o w s the Kcotenay Arc along the western margin of the P u r c e l l s . A deep c r u s t a l high c o n d u c t i v i t y l a y e r 15 to 40 km deep to the west of the t r a n s i t i o n was proposed . I t would c o n s i s t of t h e r m a l l y hydrated rock. Caner et a l . (1971) a l s o proposed an e a s t -west t r e n d i n g anomaly j u s t north of 49° and suggested that t h i s marked e i t h e r t i e n o r t h e r n margin of the h i g h l y c o n d u c t i v e upper mantle r e g i o n i n the U.S.A. (Reitze^. et a l . , 1970), or an o f f s e t i n the c r u s t a l c o n d u c t i v e l a y e r . Using new data, Dragert (1973) a l t e r e d the i n t e r p r e t a t i o n of Caner et a l . He put the c o n d u c t i v i t y l a y e r deeper, and i n c r e a s e d the complexity of the s t r u c t u r e s , p a r t i c u l a r l y i n the west. He a l s o suggested t h a t an e x t e n s i o n of the Precambrian r i f t zone of Kanasewich et al.(1969) from southern A l b e r t a i n t o the P u r c e l l A n t i c l i n o r i u m might e x p l a i n some of the data. Using the e x t e n s i o n of the r i f t zone of Kanasewich et a l . (1969) to allow f o r the magnetic and g e o l o g i c a l anomalies i n the P u r c e l l s , Berry and F o r s y t h (1975) r e a f f i r m e d the s u g g e s t i o n of Berry et a l . (1971) and Law and Riddihcugh (1971) t h a t the Rocky Mountain Trench d i d , i n f a c t , mark the c r a t o n i c margin. However, the magnetic anomalies may be more c l o s e l y r e l a t e d to heat flow o b s e r v a t i o n s than to s t r u c t u r a l models (Camfield and Gough,1975). The area from the Rocky Mountain Trench to the e a s t e r n margin of the Coast Metamorphic B e l t appears to e x p e r i e n c e moderately high heat flow, compared t o low values found to the e a s t and west (Jesscp and Judge, 14 1971). A.M. Jessop has suggested that the southern E a s t e r n Metamorphic B e l t and P u r c e l l s are an e x t e n s i o n of the n o r t h e r n U.S.A. Rocky Mountain thermal anomaly (Blackwell,1969). Because t h i s a r e a , p a r t i c u l a r l y the Eastern Metamorphic B e l t , has undergone i n t e n s i v e thermal a l t e r a t i o n s i n c e the middle Mesozoic, i t seems that the magnetic data i s more l i k e l y to be d i r e c t l y r e l a t e d to r e l a t i v e l y r e c e n t thermal anomalies, than to P r o t e r o z o i c t e c t o n i c f e a t u r e s . The p r e f e r r e d i n t e r p r e t a t i o n of the Rocky Mountain Trench p r e v i o u s l y d e s c r i b e d agrees with t h i s , a l though a c o i n c i d e n t a l l y c r i n d i r e c t l y r e l a t e d a n c i e n t t e c t o n i c f e a t u r e i s not u n l i k e l y . B a l l y et a l . (1966) i n t e r p r e t e d d e t a i l e d r e f l e c t i o n s e i s m i c work through the Rocky Mountains, and a c r o s s the Rocky Mountain Trench, at approximately the l a t i t u d e s of the p r o f i l e of t h i s study. In the Front Ranges they found a high v e l o c i t y P a l e o z o i c seguence (6.1 km/s), covered by Mesozoics (4,0 to 4,6 km/s) i n the e a s t , and o v e r l y i n g Frecambrian P u r c e l l or Windermere sediments (5.5 km/s) i n the west. These seguences are t h r u s t i n t o i m b r i c a t e sheets with an c i d e r l a y e r o f t e n o v e r t h r u s t i n g a ycunger sequence. The r e l a t i v e l y p a s s i v e basement (6.5 km/s) s l o p e s g e n t l y about 2° to the west. T h i s i n f o r m a t i o n was important i n the i n t e r p r e t a t i o n of the a r r i v a l s from s t a t i o n s near the K a i s e r shot p o i n t . The e x t e n s i o n of t h e i r r e s u l t s to the northwest i n the Main and Western Ranges, and a c r o s s the Reeky Mountain Trench where the data was poor, was d o u b t f u l . 15 I n t e g r a t i n g the g e o p h y s i c a l and g e o l o g i c a l i n t e r p r e t a t i o n s i s d i f f i c u l t , s i n c e the g e o l o g i c a l models are r a p i d l y e v o l v i n g , and i t i s not c l e a r what the g e o p h y s i c a l data r e p r e s e n t i n t e c t o n i c terms. The most prominent g e o p h y s i c a l anomalies to the west of the Rocky Mountain Trench should be r e l a t a b l e to f a i r l y r e c e n t events (since the mid-Mesozoic). The tendency to r e l y on i n v o k i n g a n c i e n t s t r u c t u r e s to model the data should be approached with c a r e ; two b i l l i o n years of t e c t o n i c a c t i v i t y with s e v e r a l i n t e n s e o r o g e n i c episodes might a l l o w l i t t l e d i r e c t evidence to s u r v i v e . T e c t o n i c r e c o n s t r u c t i c n s are a l s o m i s l e a d i n g , s i n c e t h e r e i s growing evidence t h a t l a t e r a l movements p a r a l l e l to the t e c t o n i c s t r i k e are as g e o l o g i c a l l y important as subduction and other compressional movements p e r p e n d i c u l a r to the s t r i k e . Long range s e i s m i c r e f r a c t i o n can be used to d e f i n e l a r g e s c a l e l a t e r a l and v e r t i c a l c r u s t a l f e a t u r e s with the p r e v i o u s l y d e s c r i b e d c o n s t r a i n t s cn the i n t e r p r e t a t i o n . In order to s u c c e s s f u l l y r e s o l v e these s t r u c t u r e s , Berry and F o r s y t h (1975) p r e s c r i b e d a s i g n a l - t o - n o i s e r a t i o of b e t t e r than 2 , and a r e g u l a r s t a t i o n s p a c i n g of l e s s than 20 km. 16 CHAPTER I I 1. Data A g u i s i t i q n The s e i s m i c systems used i n t h i s survey are d e s c r i b e d i n d e t a i l by Bennett (1973). Three systems designated A, B and C were deployed. Each system a m p l i f i e d and recorded s i g n a l s from v e r t i c a l , r a d i a l , and t r a n s v e r s e Willmcre Mark II seismometers with a n a t u r a l freguency of one Hertz. In order to extend dynamic range, the Geotech AS330 s e i s m i c a m p l i f i e r s have lew and high output g a i n l e v e l s s eparated by 18 to 30 dB, with a coaximum g a i n of 100 dE. Both g a i n l e v e l s f o r the v e r t i c a l and r a d i a l components, the high g a i n t r a n s v e r s e component, and two time s i g n a l s were recorded on seven channel FM tape. A c r y s t a l c l o c k s y n c h r o n i z e d with the KRV r a d i o time s i g n a l , and the KWVB b i n a r y coded decimal time s i g n a l provided t i m i n g . The shot point system c o n s i s t e d of a geophene p l a c e d w i t h i n 50 m of the b l a s t s i t e , and a two channel c h a r t r e c o r d e r monitoring i t and the WWVB time s i g n a l . The paper speed cf 4 cm/s allowed a deterrxination of o r i g i n time to w i t h i n 20 ms. Fcr some of the s h o t s , no operator was at the b l a s t s i t e and t i m i n g was achieved by r e d u c i n g a r r i v a l times from 17 the FK tapes of the MICA s e i s m i c array to the north of E e v e l s t o k e , or from the P e n t i c t c n (PNT) Canadian Standard Seismic Network s t a t i o n . Table 1 g i v e s the complete shot s t a t i s t i c s . The shot p o i n t system timing e r r o r of .02 s was based on r e a d i n g c a p a b i l i t y and the v a r i a b l e d i s t a n c e of the gecphcne from the exact b l a s t l o c a t i o n . The MICA and PNT t i m i n g e r r o r s of .04 s and .1 s t o .4 s r e s p e c t i v e l y , were assign e d on the b a s i s of the a b i l i t y to match a r r i v a l s from timed and untimed b l a s t s . Traces with a l a r g e t i m i n g u n c e r t a i n t y are marked a p p r o p r i a t e l y on the r e c o r d s e c t i o n s and the f i r s t a r r i v a l t r a v e l times were not used. The shot p o i n t s at both ends of the p r o f i l e are s c a t t e r e d over a s m a l l area. The v a r i o u s p i t s of the K a i s e r c o a l nine are up to one km a p a r t , while the Lornex and Eethlehem mines are about 5 km apart. The K a i s e r shots t y p i c a l l y c o n s i s t e d of a 200 by 100 m g r i d of 15 to 20 m d r i l l h o l e s spaced about 30 m apart and f i l l e d with e x p l o s i v e s l u r r y . The e x p l o s i o n s were not i m p u l s i v e s i n c e time d e l a y s between the d e t o n a t i o n of each s e c t i o n of holes gave t y p i c a l t o t a l time d e l a y s of 70 to 200 E S . Some m u l t i p l e b l a s t s were spread over more than one second. The Lcrnex and Bethlehem shots were s m a l l e r i n charge s i z e and a r e a l e x t e n t , but had s i m i l a r d e l a y s . The centre of the b l a s t zone and the e l e v a t i o n of the base of the d r i l l h o les were p r e c i s e l y determined through c o o p e r a t i o n of the mining companies. The u n c e r t a i n t y a s s o c i a t e d with shot l o c a t i o n e r r o r s i n the d i s t a n c e c a l c u l a t i o n s was assumed to be l e s s Table 1. Shot s t a t i s t i c s . Seme of the shots had no c o r r e s p o n d i n g s t a t i o n s . The l o c a t i o n s and e l e v a t i o n s were determined from data s u p p l i e d by the mining companies. Most t i m i n g s were determined at the s i t e , but some shots were timed remotely and have estimated t i m i n g e r r o r s g r e a t e r than .03 s. SHOT S T A T I S T I C S S H O T I ' DATE M I N E - P I T S I Z E ' L A T I T U D E LONGITUDE K I E V * T I K E (U.T.) PNT AMP.> 1- 7 3 2 - 7 3 1 - 70 2 - 70 3 - 7 U 0- 7 0 5 - 70 6- 7 0 7- 70 8- 70 9- 7 0 1 0 - 70 1 1 - 70 1 2 - 70 1 2 - 70-3 1 3 - 70 1- 7 5 2 - 7 5 3- 75 0 - 7 5 5- 7 5 6- 75 6- 7 5 - 2 7- 75 8- 7 5 9- 7 5 1 0 - 75 1 1 - 75 1 2 - 75 1 3 - 75 1 0 - 7 5 1 5 - 75 1 6 - 75 1 7 - 75 1 8 - 75 1 9 - 75 2 0 - 75 2 1 - 75 2 2 - 75 2 3 - 75 2 0 - 7 5 J U L Y 2 6 / 7 3 J O L T 2 7 / 7 3 MAY 2 1 / 7 0 HAY 2 2 / 7 0 MAY 2 0 / 7 0 J U N E 6/70 J U N E 7/70 AUG 1 2 / 7 0 AUG 1 3 / 7 0 S E P T 0/70 S E P T 0/70 S E P T 5/70 S E P T 5/70 S E P T 6/70 s S E P T 6/70 MAY 6/75 MAY 7/75 MAY 8/75 MAT 9/75 MAY 9/75 MAY 2 7 / 7 5 MAY 2 7 / 7 5 MAY 2 8 / 7 5 MAY 2 9 / 7 5 MAY 2 9 / 7 5 MAY 3 0 / 7 5 MAY 3 0 / 7 5 J U N E 1 7 / 7 5 J U N E 1 7 / 7 5 J U N E 1 8 / 7 5 J U N E 1 9 / 7 5 J U N E 2 0 / 7 5 J U N E 2 0 / 7 5 J U N E 2 5 / 7 5 J U N E 2 5 / 7 5 J U N E 2 6 / 7 5 J U N E 2 7 / 7 5 J U N E 2 7 / 7 5 J U N E 2 7 / 7 5 K A I S E R - A D I T 2 9 K A I S E R - H A R M E R 1 K A I S E R - H ARMER2 K A I S E R - A D I T 2 9 K A I S E R - A D I T 2 9 K A I S E R - A D I T 2 9 K A I S E R - H A R M E S 2 K A I S E P - H A R M E R 2 K A I S E R - A D I T 2 9 B E T H L E H S M - H U E S T I S LORNEX BETH L E HEM-HU E S T is' LORNEX K A I S E R - H A P M E R 2 B E T H L E H E M - J E R S E Y LORNEX B E T H L E H S M - H U E S T I S K A T S E P - H A P M E R 2 B E T H L E H E M - H I E S T I S K A I S E R - A D I T 2 9 K A I S E R - H A R H E B 2 LORNEX L C R N E X K A I S E R - A D I T 2 9 L C R N E X K ATSE R - A D I T 2 9 L C P N E X K A I S E R - 1 6 SEAM LORNEX LOPNEX K A I S E R - H A P M E R 2 K A I S E R L C F N E X B E T H L E H E M - H U E S T I S L C R N E X L C R N E X B E T H L E H E H - I O N A K A I S E R L C R N E X 1 5 0 0 9 . 7 5 2 5 150 0 9 . 7 7 7 3 261 09. 7 8 0 8 2 3 0 09. 7 5 8 2 2 5 0 0 9 . 7 5 0 3 1 6 0 0 9 . 7 6 0 7 2 5 5 0 9 . 7 8 8 8 2 0 3 0 9 . 7 8 8 5 0 6 7 0 9 . 7 5 9 8 9 5 0 . 0 9 7 0 0 3 5 0 . 0 5 8 3 28 50. 0 9 5 8 31 5 0 . 0 5 5 2 100 0 9 . 7 9 0 5 300 0 9 . 7 8 9 3 01 5 0 . 0 9 6 2 60 50. 0 5 0 8 27 5 0 . 0 9 5 7 3 0 0 09. 7 8 7 8 20 5 0 . 0 9 5 8 6 0 0 0 9 . 7 5 6 3 2 2 0 09. 78 37 2 1 5 0 9 . 7 8 7 8 19 50. 0 5 3 7 19 50. 0 5 8 0 2 5 0 0 9 . 7 5 0 7 27 5 0 . 0 5 5 7 2 0 0 0 9 . 7 6 1 2 10 5 0 . 0 5 3 0 5 0 0 9 . 7 5 0 8 OMITTED OMITTED 115 0 9 . 7 8 7 8 7 0 9. 76 08 37 50. 0 5 0 5 ? 5 0 . 0 9 5 3 38 50. 0 5 5 3 17 50. 0 5 2 7 26 50. 0 9 3 7 ? 09. 7 5 5 7 01 50. 0 5 8 2 1 1 0 1 1 0 , 1 1 0 . 1 1 0 . 1 1 0 , 1 1 0 . 1 1 0 . 1 1 0 , 1 1 0 . 1 2 0 . 1 2 1 . 1 2 0 . 1 2 1 . 1 1 0 . 1 1 0 . 1 2 0 . 1 2 1 . 1 2 0 . 1 1 0 . 1 2 0 . 1 1 0 . 1 1 0 . 1 1 0 . 1 2 1 . 1 2 1 . 1 1 0 . 1 2 1 . 1 1 0 . 1 2 1 . 1 1 0 . . 8 1 0 5 . 8303-. 8 3 6 7 . 8 1 6 5 . 8 0 8 3 . 8 1 7 8 . 8 3 2 8 . 8302 . 8 1 5 0 . 9906 . 0 0 0 0 . 9 9 0 9 . 0 0 6 3 . 8 1 5 5 . 8 3 7 7  9 8 2 6 . 00 18 . 9971 . 8362 . 9 9 8 1 . 81 53 . 83 53 . 8 3 2 2 .0000 , 0 0 7 9 .8108 ,00 18 . 8 1 8 3 . 0 3 9 7 8 3 6 3 1 1 0 . 8 3 2 2 1 1 0 . 8 1 8 1 1 2 1 . 0 0 1 0 1 2 0 . 9 9 0 3 1 2 1 . 0 0 8 3 1 2 1 . 0 0 0 5 1 2 0 . 9 7 8 7 1 1 0 . 8 3 6 7 1 2 1 . 0 0 8 0 6 3 7 0 6 3 7 0 6 3 7 0 6 2 7 0 6 2 2 0 6 2 2 0 6 3 7 0 6 2 9 5 6 2 2 0 0 0 0 0 0 6 7 2 0 3 3 3 0 7 5 2 6 3 20 6 3 2 0 0 9 6 7 0 6 3 2 0 2 6 7 6 3 2 0 0 2 6 7 6 1 7 0 6 2 7 0 6 2 7 0 0 6 7 2 0 7 5 2 6 1 7 0 0 6 3 2 6 1 2 0 0 6 7 2 6 1 5 0 6 1 5 0 6 1 5 0 0 6 3 2 0 0 3 3 0 7 1 2 0 7 1 2 5 0 3 3 6 1 5 0 0 7 5 2 19: 58 1 8 : 1 5 18: 3 3 2 0 : 58 1 8 : 1 2 2 1 : 0 3 1 8 : 38 1 8 : 1 9 2 0 : 5 8 1 9 : 0 2 2 2 : 50 1 9 : 0 2 2 2 : 5 5 :08. 9 3 t . 02 : 1 0 . O l t . 0 2 :08. 6 7 * . 02 :02. 9 6 * . 02 : 1 0 . 8 5 * . 0 3 :03. 2 8 t . 02 : 0 8 . 1 3 * . 02 : 2 3 . 0 7 t . 0 2 :07. 7 3 t . 0 0 : 12. 9 0 t . 02 : 28. 0 8 i . 02 : 32. 9 9 t . 0 0 : 5 0 . 8 7 * . 0 0 18: 1 ? : 2 5 . 8 1 1 . 0 0 1 9 : 0 8 : 3 1 . 31±. 0 2 2 2 : 5 5 : 5 5 . 2 2 t . 0 0 1 8 : 5 9 : 5 0 . 0 9 * . 0 0 NO T I M I N G 1 9 : 0 5 : 2 2 . 3 5 * . 02 2 1 : 0 2 : 1 8 . 5 7 * . 0 0 2 0 : 0 1 : 13. 0 2 * . 00 2 2 : 58 :27. 0 0 * . 0 2 2 2 : 5 7 : 5 8 . 8 5 * . 0 2 2 1 : 0 1 : 1 7 . 1 0 * . 1 0 2 2 : 5 3 : 17. 5 2 * . 0 2 2 1 : 0 7 : 0 9 . 5 0 * . 00 2 2 : 5 7 : 2 7 . 0 5 * . 0 2 1 8 : 1 5 : 3 8 . 0 5 * . 0 2 1 8 : 16: 2 0 : 5 9 : 2 2 : 5 7 ; 1 9 : 0 6 : 2 2 : 5 8 : 2 2 : 5 0 ; 1 9 : 2 9 : 2 0 : 5 1 : 2 2 : 5 3 : 3 3 . 5 1 * . 0 2 5 5 . 9 5 * . 00 0 6 . 3 2 * . 0 2 5 1 . 2 2 * . 0 2 35. 3 6 * . 02 0 3 . 3 1 * . 02 5 5 . 5 0 * . 0 2 0 2 . 6 7 * . 0 0 38. 5 7 ± . 0 2 0. 1 2 . 9 2 . 9 0.9 0.5 3. 9 5. 6 0. 0 6.5 0. 5 2 0 1. 1 2 . 1 5. 3 1 . 9 6. 0 3. 8 2 . 5 1. 0 0. 8 1.6 0. 5 1.0 0. 8 5 . 8 6. 3 2 . 5 2 . 3 0 . 5 8. 8 • S I Z E - THE T C T A L SHOT H E I G H T I N THOUSANDS OP POUNDS * E L E V - THE E L E V A T I O N OP THE BOTTOM OF THE SHOT HOLE I N F E E T ABOVE SEA L E V E L » P N T AMP. - THE PEAK TO PEAK A M P L I T U D E OF THE P - A E B I V A L MEASURED I N CH. FROM PNT P A P E R RECORDS (CORRECTED FOR INSTRUMENT RESPONSE) • * DENOTES S C A L E A M P L I T U D E S D E T ERMINED FROM MICA ARRAY • M U L T I P L E B L A S T ( T I M I N G G I V E N FOR F I R S T B L A S T ) 20 than .1 km. The r e c o r d i n g s i t e s were p r e f e r a b l y l o c a t e d on bedrock outcrops found near access roads, as c l c s e to the p r o f i l e l i n e as p o s s i b l e . F i g u r e 1 i l l u s t r a t e s the l i n e , with the c l o s e d c i r c l e s i n d i c a t i n g s t a t i o n s which recorded K a i s e r s h o t s , and with open c i r c l e s shewing those which recorded Highland V a l l e y s hots. Tables 2a and 2b give the s t a t i s t i c s of those s t a t i o n s used i n the i n t e r p r e t a t i o n . The s t a t i o n l a b e l s are d e r i v e d frcm the system i d e n t i f i c a t i o n (A, B or C ) , the shct number, and the year of the f i e l d season. The s i t e s were l o c a t e d u s i n g 1:50000 t o p o g r a p h i c maps, a e r i a l photographs, and P r o v i n c i a l F o r e s t Inventory Maps. The r e s u l t i n g e r r o r s i n the c a l c u l a t i o n of d i s t a n c e s were g e n e r a l l y l e s s than .2 km with a few e x c e p t i o n s as noted l a t e r . The s e i s n i c s t a t i o n s were c o r r e c t e d to an e l e v a t i o n datum of one km above sea l e v e l by assuming a 5.3 km/s near-s u r f a c e v e l o c i t y , and a 6.0 or 8.0 km/s i n f e r r e d r e f r a c t o r v e l o c i t y . System and environmental n o i s e c o n t a m i n a t i o n , poor t i m i n g , system m a l f u n c t i o n , l o g i s t i c a l prcblems, and d u p l i c a t i o n r e s u l t e d i n a severe r e d u c t i o n i n the t o t a l number of r e c o r d i n g s a c t u a l l y used i n the i n t e r p r e t a t i o n . F i f t e e n of a t o t a l of n i n e t e e n K a i s e r shots were used f o r 34 s u c c e s s f u l r e c o r d i n g s . E i g h t e e n of a t o t a l of twenty Highland V a l l e y shots were used f c r 41 s u c c e s s f u l r e c o r d i n g s . Table 2a. K a i s e r s t a t i o n s t a t i s t i c s . The l o c a t i o n s and e l e v a t i o n s were mainly determined from 1:50000 t o p o g r a p h i c maps. The f i r s t a r r i v a l times were determined from the analog output. The column PICT i n d i c a t e s whether the t r a c e was i n c l u d e d i n the f i n a l r e c o r d s e c t i o n and whether the analog t r a v e l time i n f o r m a t i o n was used i n the delay time and f i r s t a r r i v a l time a n a l y s i s . Many t r a v e l time p i c k s on noisy t r a c e s were c o n s i d e r e d erroneous. KAISER PROFILE STATISTICS S I T E C137S A77<4 C774 C1675 A474 C674 A674 A1373 A1675 A574 A2375 B774 B1675 C2375 A173 C173 3674 A273 C273 B273 A177a C177j A374 A274 A975 C274 B27U C975 C174 B374 C37U C474 8474 C574 LATITUDE LONGITU DE 4 9 . 7 7 1 7 7 4 9 . 8 1 3 5 1 "4 9. 814550 1 9 . 7 5 7 9 3 4 9 . 7 8 C 1 7 «9.78i416' U 9 . e 3 7 0 1 4 9 . 7 3 5 4 6 a s . 7 C5 en 149 . 7 3 167 <4 9 . 706U8 4 9 . 7 5 3 3 4 149. 7 1776 14 9 . 76146 3 <4 9. 9 38 17 5 0 . C 4 C 0 8 4 9 . 9 8 7 3 4 5 0 . 1 2 1 0 6 5 0 . 1 2 3 0 0 5 0 . 1 1 6 3 3 119.90125 4 9 . 9 3 0 3 6 H9 .61551 5 0 . 0 9 1 7 5 5 0 . 191400 5 0 . 2 U 1 5 0 5 C . 2 6 5 0 0 5 0 . 2 6 5 0 0 5 0 . 3 5 4 6 8 5 C . 3 5 C 0 1 5 0 . 3 3 9 6 8 5 0 . 3 8 1 0 0 50.148927 5 0 . D 7 5 6 9 11U. 91401)14 1 1 5 . 1 3 9 3 3 1 1 5.214583 1 1 5 . 3 8 7 C 5 1 1 5 . 5 1 6 6 6 1 1 5 . 6 7 7 6 7 1 1 5 . eo«3u 1 1 5 . 9 8 2 8 0 1 16 . 223314 116 . 110568 .1 16 . 62277 1 1 6 . 7 0 0 0 0 1 16. 823 e« 1 1 6 . 9 0 9 7 4 1 1 6 . 9 4 7 3 3 117 . 127143 1 1 7 . 3 5 2 0 1 1 1 7 . 5 0 8 8 2 117 . 761314 1 1 8 . C0917 1 1 8 . 0 8 6 1 2 118.23UI47 I 1 8 . 3014 314 118.U733U II 8 . 568214 118 . 6 3 6 2 8 118 . 8 2 2 e 3 118.e22 e3 119 . 0 9 8 0 1 119 . 5 1 6 6 6 1 1 9 . 9 5 9 8 2 1 2 0 . 3 0 1 3 3 1 2 0 . 4 7 0 2 1 1 2 0 . 9 5 0 3 9 DISTANCE TIME* ELEV* E-C03' LO-CUT* HI-CUT PLOT* TTIDLE SCIDLl 7.296 1.62 4050 -.11 0.75 12.50 Y Y -. 15 1.00 24. 197 4. 32 4000 -.11 0.75 12. 50 Y Y -. 10 1. 00 32.553 5.65 . 4400 -.13 0.75 12.50 t Y -.18 1. 00 40. 141 6.99 5100 -.15 0. 75 12. 50 Y Y 0.0 0.50 50.40 2 8. 62 5100 -.15 0. 75 12.50 ' Y Y 0.0 1. 00 60. 80 1 10. 33 2900 -.08 0.75 12.50 Y Y : 0.0 1. 00 70.115 11.88 2950 -.08 0. 75 7.00 Y Y 0.0 1.00 82.754 13.00 5500 -.16 0. 75 7.00 1 Y 0.0 1.00 100.780 17. 09 5600 -.16 1. 50 6.00 I I 0.0 0. 50 113.664 18.88 3800 -.11 0.75 10.00 Y Y -.30 1.00 130.324 0.0 4900 -.14 0. 80 8.00 Y N 0.70 1. 00 135.993 22. 82 5900 -.17 0.75 12.50 Y Y 0.0 • 1. 00 143.877 24. 39 3700 -.10 0. 75 6.00 Y Y 0.0 1.00 150. 79 1 0. 0 1900 -.05 0. 80 8.00 N N 0.0 1. 00 155. 203 26. 07 6262 -.19 0. 75 8.50 Y Y 0.0 1. 00 169.653 28.72 3750 -.11 0. 75 12. 50 Y Y 0.0 10. 00 182.435 30.44 2900 -.12 0. 75 8.00 Y Y 0.0 1.00 196. 176 32. 34 2450 -.10 0.75 12.50 Y Y 0.0 1. 00 214.015 3 4.64 2100 -.09 0. 75 7.50 Y Y 0.0 10. 00 23 1. 44 1 36.54 2950 -.12 0. 80 7.00 Y Y 0.0 1.00 234.578 0. 0 1700 -.06 0.80 7. 50 Y N 0.0 0. 25 245.326 0. 0 3950 -.16 0. 75 7. 50 Y N 0.0 0. 25 252.071 39.47 3150 -.13 0.75 6.00 Y Y 0.0 1.00 26 5. 40 9 40.99 4100 -.17 0. 75 6.00 Y Y 0.0 1. 00 273. 94 3 4 1.. 9 1 2700 -.10 0. 80 8.00 Y Y 0.0 0. 25 279.297 C O 1950 -.07 0.75 '6.00 Y N 0.0 1.00 292.e66 44. 24 2300 -.09 0. 75 6.00 Y Y 0.0 1. 00 293.164 0.0 2300 -.09 0.80 6.00 N N 0.0 1.00 311.637 46.73 5050 -.22 0. 75 7. 50 Y Y 0.0 2. 00 343.997 50. 83 3200 -.13 0. 75 5.20 Y Y 0.0 1. 00 375.023 54. 93 3150 -.13 0.75 7.50 Y Y 0.0 1.00 398.842 57.67 2900 -.11 0.75 5.00 Y N 0.0 1. 00 412.502 59. 90 4200 -.17 0.75 5.00 Y N 0.0 1. 00 442. 742 64. 00 4050 -.17 0.75 5.00 Y N 0.0 1.00 'TRAVEL TINE IK SECONDS IS DETERMINED EROH ANALOG PLAYBACKS A ZEdC IMPLIES THAT NC TIME CCULD EE DETERMINED ^ELEVATION CP THE RECORDING S I T E IN FEET ABOVE SEA LEVEL (FROM 1:50000 BAPS) J E L E V ATICN CCRRECIION I!l SECCNDS TO A CNE K K DATUt! (APPLIED TC ELOTS FOR DISTANCES OVER 80 KB) THE CCRRECTICK IS SOT INCLUDED IN THE TRAVEL TIMES REPORTED IN THIS TABLE •LO-CUT AND HI-CUT ARE THE LIMITS IN HERTZ CF THE BANDPASS FILTER USED CN THE FILTERED BECOBO SECTIONS *THE FIRST COLOMN CF ELCT SPECIFIES WHETHER OR NOT (Y OR N) I HE TRACE IS INCLUDED IN THE FINAL SECTION THE SICCND COLUMN SIMILARLY S F E C I F I E S IF THE ANALOG TRAVEL TIME INFORMATION HAS USED Table 2b. Highland V a l l e y s t a t i o n s t a t i s t i c s . The l o c a t i o n s and e l e v a t i o n s wsre mainly determined from 1:50000 topo g r a p h i c maps. The f i r s t a r r i v a l times were determined from the analog output. The column PLOT i n d i c a t e s whether the t r a c e was i n c l u d e d i n the f i n a l r e c o r d s e c t i o n and whether the analog t r a v e l time i n f o r m a t i o n was u s e f u l . Many t r a v e l time p i c k s cn n c i s y t r a c e s were c o n s i d e r e d erroneous. H I G H L A N D V A L L E Y P R O F I L E S T A T I S T I C S S ITS . LAT ITUDE LONGITUDE A87tt A 97 4 C874 C974 8874 B974 A1074 A 1174 C1074 C U 74 B1074 B 11 71* A 1374 C1374 A275 A175 B 1 2 7 5 C275 C 1 2 7 5 A 12 75 B U 7 5 C 4 7 5 A775 B 8 7 5 C875 A875 C1075 A 1075 B21 75 C 1 3 7 5 A 21 75 A 1875 C2175 A 1 9 7S A 20 75 C1975 C2075 B2075 C2275 A 2 2.75 A 24 75 50. 47569 50. 47569 50 .4P560 50. 48560 50. 47029 50. 47029 50 .48151 50. 48151 5 0 . 4 6 5 6 7 5 0 . 4 5 6 6 7 50. 45000 50. 45000 5 0 . 4 3 8 0 5 50. 38 100 50. 34550 50. 34550 5 0 . 3 2 4 5 8 50. 33 968 5 0 . 3 « 4 5 2 50. 42976 .50. 35739 5 0 . 3 8 3 0 0 50. 3U575 50 . 34575 50. 34354 50. 35309 50 .26500 5 0 . 1 " H 0 0 5 0 . 0 6 6 5 7 4 9 . 93036 4 9 .93036 4 9 . 90125 4 9 . 9 0 1 2 5 50 . 06081 50 . 06081 50 . 13155 50. 13155 49. 98? 33 49. 76463 4 9 . 70648 49 . 70648 1 2 0 . 9 5 0 4 2 1 2 0 . 9 5 0 4 2 120 .88460 120 .88460 120.81161 120.81161 1 2 0 . 7 3 0 0 0 120 .73000 1 2 0 . 6 4 9 9 9 120. 64999.^ 1 2 0 . 5 3 3 3 3 1 2 0 . 5 3 3 3 3 120. 39127 120. 301 33 120 .28320 1 2 0 . 2 8 3 2 0 119 .99663 119 .95982 1 1 9. 32585 1 1 9 . 6 2 ^ 2 9 1 1 9 . 5 1 0 7 0 1 1 9 . 3 4 0 6 7 119 .20061 119 .20061 119 .11406 1 1 8 . 9 2 3 1 6 118 .82283 118 .56824 .1 1 8. 435 33 1 1 3 . 2 3 4 4 7 1 1 8. 23447 118 .08612 118. 086 12 117 .79668 117 .79658 1 1 7 . 5 3 3 0 7 1 1 7 . 5 3 3 0 7 117 .34902 116 .90974 1 1 6 . 6 2 2 7 7 1 1 6 . 6 2 2 7 7 DISTANCE T I H E 1 ELEV* E - C O R » 4. 399 0. 70 ' 4050 - . 0 6 7. 296 1.07 4050 - . 0 7 3. 519 1. 42 3900 . - . 0 5 12. 048 2. 07 3900 - . 0 6 13. 560 2.53 3300 . - . 0 4 16. 896 3. 11 3300 - . 0 4 19. 050 3. 29 3850 - . 0 5 22. 860 3.86 3850 - . 0 6 24. 887 4. 39 4000 - . 0 6 28. 34 1 4. 90 4000 - . 0 7 33. 287 5.62 4500 - . 0 7 36 .610 6. 10 4500 - . 0 8 42. 540 7.23 3600 - . 0 6 50. 161 8. 64 3100 - . 0 5 53 . 521 9. 64 3800 - . 0 5 55 . 387 ' 9.88 3800 - . 0 6 75. 627 12.60 3350 - . 0 5 7 5 . 8 8 2 12.71 3150 . - . 0 3 8 6 . 6 0 3 0. 0 2300 - . 01 1 0 0 . 4 6 7 16. 45 3400 - . 0 5 106 .953 1 7. 85 3200 - . 0 3 118. 520 19.65 2050 0.01 131 .433 22. 26 3200 - . 0 4 132. 039 22. 35 3200 - . 0 4 138. 199 23. 30 4500 - . 0 8 151.591 25. 00 2500 - . 0 2 159. 463 26 . 07 2300 - . 0 1 1 7 8 . 6 9 7 28. 78 2700 - . 0 2 191. 102 0. 0 4200 - . 1 0 208. 923 32. 58 3950 - . 0 9 2 0 9 . 0 7 3 32. 84 3950 - . 0 9 220 . 069 34. 07 1700 0.01 2 2 0 . 2 2 2 34. 32 1700 0.01 233. 191 0. 0 2500 - . 0 2 236. 182 38. 69 2500 - . 0 3 2 5 0 . 0 5 7 0.0 2450 - . 0 1 25 3. 278 40 . 24 2450 - . 0 3 2 6 9 . 4 0 0 0. 0 2900 - . 0 5 3 0 2 . 2 6 0 0. 0 1900 - . 02 3 2 3 . 9 5 8 4 7 . 01 4900 - . 15 327. 850 0. 0 4900 - . 14 ELEV* E-C R* LO-COT* H I -CUT PLOT* T T I D L E S C I D L E 0.75 0. 75 0. 75 0. 75 0. 75 0. 75 0. 75 0. 75 0. 75 0. 75 0. 75 0. 75 0. 75 0. 75 0. 75 0. 75 0. 75 0. 75 0. 75 1. 00 0. 75 0. 75 0. 75 0. 75 2. 70 2.70 0. 75 0. 75 1. 00 0. 75 0. 75 0.75 0. 75 1. 50 0. 75 1. 50 0. 75 0. 80 1. 50 1. 00 1. 00 12. 50 12 .50 12. 50 12. 50 12. 50 12. 50 12. 50 12 .50 12. 50 12. 50 12. 50 12. 50 12. 50 12. 50 12. 50 12. 50 12. 50 .12.50 5. 20 12.00 5 .50 9. 50 10. 60 10 .60 10.00 10.00 10. 00 12. 50 5. 50 12.00 12.00 5. 50 5. 50 4 .00 12.00 4 .00 5.50 5. 50 5.00 5. 50 6. 00 I Y I Y Y Y Y Y Y Y 1 Y Y Y Y Y N Y Y Y Y Y Y Y Y Y Y Y Y N Y N N Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y N Y Y Y Y Y . Y Y Y Y N N Y 0.0 - . 2 0 0 .05 - . 22 0 0 0 05 0 - . 0 5 - . 0 5 0. 92 0 .05 - . 0 2 0. 10 0 .0 0.0 - . 0 8 0 .0 0 .0 0 .0 0 .0 0 .0 0 . 0 0 .0 0.0 0 .0 0 .0 0. 10 0.0 0 .0 0 .0 0.0 0.0 0 .0 . 0.0 0 .0 0 .0 0.0 0 . 0 0 .0 1. 00 1. 00 1. 00 1. 00 1. 00 0. 25 1. 00 1. 00 1. 00 1. 00 1. 00 1. 00 1. 00 1. 00 1. 00 1. 00 1. 00 1. 00 0. 50 0. 50 1. 00 1. 00 1. 00 1. 00 1. 00 1. 00 ' 1. 00 1. 00 1.00 1.00 1.00 1. 00 1. 00 1. 00 1. 00 1. 00 1. 00 1. 00 1. 00 1. 00 1. 00 • T R A V E L T I K E I N S E C O N D S IS D E T E R M I N E D F R O H ANALOG P L A Y B A C K S A Z E R O I M P L I E S T H A T NO T I K E C O U L D B E D E T E R M I N E D ^ M ^ 0 5 1 ° F ™ S R S C 0 * D I ! , G S I T E I N F E E T A B O V E S E A L E V E L (FPOM 1-50000 MAPS) lllZlr\ll°" C 0 P R - C T I 0 N ™ S E C O N D S TO A ONE KM D A T U H ( A P P L I E D TO P L O T S FOR D I S T A N C E S OV-R 8 0 K H l T R E C O R R E C T I O N I S NOT I N C L U D E D TN T H E T R A V E L T I M E S R E P O R T E D I N T 5 K T » B L » ' 25 2. P j e l i j i n a r i A n a l y s i s The FM f i e l d tapes were e d i t e d onto a master tape and subsequently d i g i t i z e d . Four channels (three s e i s m i c p l u s time) were i n p u t to a 14 b i t a n a l o g - t o - d i g i t a l c c n v e r t o r system with magnetic tape output. The system i n c l u d e d a Hewlett Packard FM playback u n i t , a m o d i f i e d A n a l o g i c Corp. AN5800 A-D c o n v e r t o r , a Kennedy 8108 9-track d i g i t a l tape t r a n s p o r t with a Kennedy 8230 b u f f e r e d f o r m a t t e r , and c o n t r c l - i n t e r f a c e l o g i c c i r c u i t s . The e f f e c t i v e d i g i t i z a t i o n r a t e was 62.5 Hz with minor v a r i a t i o n s due to FM tape speed f l u t t e r i n g and tape s t r e t c h i n g . An average sample r a t e was determined from the f i r s t 24 seconds of data and used i n the a n a l y s i s . The average d i g i t i z i n g r a t e was not e x a c t , and i n order to improve the appearance of the f i n a l r e c o r d a c t i o n , a time c o r r e c t i o n i n c l u d e d i n Table 2 as TTIDLE was used. I t was determined by matching the analog and d i g i t a l a r r i v a l times and i t s e f f e c t i s p r i m a r i l y a e s t h e t i c . Power s p e c t r a l a n a l y s i s , u s i n g a t r u n c a t e d a u t o c o r r e l a t i o n power e s t i m a t e , showed t h a t most of the s e i s m i c energy, on the m a j o r i t y of t r a c e s , was between 2 and 4 Hz. There was c o n s i d e r a b l e s i g n a l o u t s i d e of t h i s pass band, however, so t h a t to preserve the g u a l i t y of the f i r s t break, c n l y t r a c e s t h a t showed s i g n i f i a n t n o i s e were band passed. For u n f i l t e r e d t r a c e s the f i e l d system a m p l i f i e r c u t o f f s of .75 and 12.5 Hz at the -6 dB l e v e l are guoted i n 26 Table 2. The d i g i t a l f i l t e r l i m i t s were s e t t o e l i m i n a t e the n o i s e spectrum determined from the f i v e seconds of noise preceding the f i r s t a r r i v a l . A f o u r t h c r d e r zero-phase Butterworth f i l t e r (Kanasewich, 1975) was used t c bandpass the t r a c e s . In some cases c r o s s - t a l k between the time channels and the s e i s m i c channels caused c o n s i d e r a b l e n o i s e c o n t a m i n a t i o n w i t h i n the frequency l i m i t s of the s i g n a l . Maximum E n t r o p y -(MEM) s p e c t r a l a n a l y s i s (Dlrych and Bishop,1975) was used to c l o s e l y r e s o l v e the n c i s e and s i g n a l s p e c t r a i n order t h a t a notch f i l t e r might be a p p l i e d . However, the s i g n a l - t o - n o i s e r a t i o was not improved by the notch f i l t e r and the a r r i v a l s were d i s t o r t e d . As a compromise, a narrow bandpass with a width of a few Hertz was a p p l i e d to these t r a c e s . Amplitude c o r r e c t i o n f a c t o r s due to the system a m p l i f i e r responses were c a l c u l a t e d from the f i e l d g ain s e t t i n g s . The energy y i e l d - o f the b l a s t s was a l s o e s t i m a t e d by determining the amplitude c f the f i r s t a r r i v a l on the PNT r e c o r d s . T h i s s t a t i o n i s south of the p r o f i l e , but the azimuths r e l a t i v e to the shot s i t e s were judged to be c l o s e enough to the p r o f i l e d i r e c t i o n t h a t the amplitude estimate would be reasonable., No e t h e r permanent s t a t i o n c o u l d give e q u i v a l e n t data. However, because the FNT s t a t i o n was i n o p e r a b l e f o r a s h o r t time d u r i n g the f i e l d work, some; of the shots were s c a l e d from MICA a r r a y a r r i v a l s as i n d i c a t e d i n Table 1. Although charge s i z e s were i n c l u d e d i n Table 1 f c r comparison, they were net used d i r e c t l y i n the s c a l i n g . 27 but they d i d help i n d i c a t e some d i f f i c u l t i e s . The s c a l e adjustment f a c t o r SCIDLE i n Table 2 was used t c c o r r e c t p o s s i b l e e r r o r s i n f i e l d a m p l i f i e r s e t t i n g s , and to allow f o r i n a p p r o p r i a t e shot y i e l d f a c t o r s . I t was assumed t h a t , a f t e r s c a l i n g , the amplitudes should vary more or l e s s smoothly along the p r o f i l e , and t h a t they should be independent of the shot. Using t h i s c r i t e r i o n , r e c o r d i n g s of shots 9-75, 12-75, 16-75 and 17-1/5 were amplitude c o r r e c t e d by the a d d i t i o n a l f a c t o r SCIDLE. These g u a l i t a t i v e l y j u s t i f i a b l e adjustments are s i m i l a r to the TTIDLE f a c t o r i n that t h e i r e f f e c t i s more a e s t h e t i c than s u b s t a n t i a l . The t r a c e s were d i g i t a l l y e d i t e d and compiled i n t o the f i n a l f i l t e r e d r e c o r d s e c t i o n s , shown i n F i g u r e s 2, 3 and 4. Question marks placed a f t e r the t r a c e l a b e l imply t h a t the t i m i n g f o r the t r a c e was only approximate, so t h a t only the amplitude i n f o r m a t i o n i s r e l e v a n t . The s m a l l h o r i z o n t a l t i c s on the t r a c e s correspond to the f i r s t a r r i v a l times as picked from the seven channel FM playbacks. The a n a l c g r e c o r d s were g e n e r a l l y e a s i e r t c pick than the d i g i t a l t r a c k s . Only the p i c k s which were reasonably c l e a r were p l o t t e d ; the f u l l s e t of data was i n c l u d e d i n Table 2. F i g u r e s 2 and 3 are f u l l r e c o r d s e c t i o n s c f K a i s e r and Highland V a l l e y s h o t s , while F i g u r e H i s an enlargement of the near source t r a c e s i n Highland V a l l e y , with a 6 km/s r e d u c i n g v e l o c i t y . In order to enhance the head waves r e l a t i v e to the body waves, an R 2 g e o m e t r i c a l s p r e a d i n g f a c t o r was i n c l u d e d i n the amplitude s c a l i n g . A few a p p a r e n t l y unreasonable d e s c r e p a n c i e s , t h a t c c u l d not be c o r r e c t e d , are mentioned as they appear i n the i n t e r p r e t a t i o n . The remaining amplitude and t r a v e l time i n f o r m a t i o n was assumed to be r e l a t e d t c g e o p h y s i c a l s t r u c t u r e a l c n g the p r o f i l e s . F i g u r e 2. K a i s e r r e c o r d s e c t i o n . The f i l t e r e d t r a c e s are amplitude c o r r e c t e d and have a R 2 f a c t o r a p p l i e d t c emphasize a r r i v a l s a t l a r g e d i s t a n c e s . The h o r i z o n t a l t i c marks on the t r a c e s mark the f i r s t a r r i v a l p i c k s from the analog output. Question marks appearing beside t r a c e names imply t h a t those t r a c e s had poor timing and provide only amplitude i n f o r m a t i o n . D I S T A N C E (KM) F i g u r e 3. Highland V a l l e y r e c o r d s e c t i o n . The f i l t e r e d t r a c e s are amplitude c o r r e c t e d and have a R 2 f a c t o r a p p l i e d to emphasize a r r i v a l s at l a r g e d i s t a n c e s . The h o r i z o n t a l t i c marks on the t r a c e s mark the f i r s t a r r i v a l p i c k s from the analog output. Question marks appearing beside t r a c e names imply that those t r a c e s had poor t i m i n g and provide only amplitude i n f o r m a t i o n . 00 D I S T A N C E (KM) F i g u r e 4. Near s o u r c e H i g h l a n d V a l l e y s e c t i o n . The f i r s t s e venteen t r a c e s o f F i g u r e 1 a r e d i s p l a y e d w i t h a r e d u c i n g v e l o c i t y o f 6 km/s. The f i l t e r e d t r a c e s are a m p l i t u d e c o r r e c t e d and have a R 2 f a c t o r a p p l i e d t o emphasize a r r i v a l s at l a r g e d i s t a n c e s . The h o r i z o n t a l t i c marks on the t r a c e s mark the f i r s t a r r i v a l p i c k s from the a n a l o g o u t p u t . C M H I G H L A N D V A L L E Y DISTANCE (KM) 35 CHAPTER I I I 1. Frj5liminar_y I n t j r _ c r e t a t i o n S e v e r a l f a c t o r s encouraged a r e l a t i v e l y simple approach t c the i n t e r p r e t a t i o n . The p r o f i l e has obvious l a t e r a l d i s c o n t i n u i t i e s with few e t h e r g e o p h y s i c a l c o n s t r a i n t s . More s o p h i s t i c a t e d approaches t o s e i s m i c modelling of these s t r u c t u r e s are not r e a d i l y a v a i l a b l e . In any event, the very non-impulsive nature of the sources, together with the lew frequency of the r e c o r d i n g s , l i m i t s the r e s o l u t i o n to a few k i l o m e t e r s at depths c o r r e s p o n d i n g to the H-d i s c o n t i n u i t y . Timing equipment m a l f u n c t i o n s , inclement weather, i n t e r f e r i n g s e i s m i c a r r i v a l s from ether u n i d e n t i f i e d b l a s t s , and u n c e r t a i n s i t e l o c a t i o n i n p o o r l y mapped and r a p i d l y changing areas a l l c o n t r i b u t e d t c make much c f the data of i n d i f f e r e n t q u a l i t y . D espite these d i f f i c u l t i e s , s e v e r a l i n t e r e s t i n g f e a t u r e s are d e f i n e d or suggested by t h i s experiment. Common assumptions about observed a r r i v a l s were used i n the i n t e r p r e t a t i o n s . A r r i v a l s with an apparent v e l o c i t y of 7.5 km/s cr g r e a t e r were i n t e r p r e t e d k i n e m a t i c a l l y as c r i t i c a l r e f r a c t i o n s from the M - d i s c o n t i n u i t y . Amplitude 36 modelling r e q u i r e d the more c o r r e c t dynamic r e p r e s e n t a t i o n of these waves as i n t e r f e r e n c e or d i f f r a c t i o n head waves ( E r a i l e and Smith, 1975; Cerveny, 1966). Phases with apparent v e l o c i t i e s c f 4.5 to 6.1 km/s were assumed to be k i n e m a t i c a l l y behaving l i k e s u b - c r i t i c a l l y and c r i t i c a l l y r e f r a c t e d waves i n the upper c r u s t . Dynamically they may be a grcup of a r r i v a l s c o r r e s p o n d i n g t c the sum of m u l t i p l e r e f l e c t i o n s i n the c r u s t a l wave guide (Berry and F o r s y t h , 1975). Intermediate l a y e r s with v e l o c i t i e s from 7.0 to 7.4 km/s were t e n t a t i v e l y i d e n t i f i e d , although c n l y second a r r i v a l s were observed on the K a i s e r record s e c t i o n . The p r e l i m i n a r y d e t e r m i n a t i o n of the v e l o c i t i e s and depths cf these l a y e r s was made from l e a s t squares f i t s t o the f i r s t a r r i v a l t r a v e l times. Simple models from s t r a i g h t l i n e f i t s t c the a r r i v a l s suggested the b a s i c s t r u c t u r e and i d e n t i f i e d i n t e r p r e t a t i o n a l d i f f i c u l t i e s . The f i r s t a r r i v a l times picked frcm the analog r e c o r d s are p l o t t e d i n F i g u r e 5 along with the topography and a c r o s s - s e c t i o n of the n e a r - s u r f a c e geology. The l i n e s were f i t t e d u s i n g a weighted g e n e r a l i z e d l e a s t sguares program adapted by Ahem (1975) from a program d e s c r i b e d by York (1969). Weights were computed from e s t i m a t e s of the e r r o r s i n d i s t a n c e and time a s s o c i a t e d with each o b s e r v a t i o n . The u s u a l e r r o r assigned to the d i s t a n c e was .2 km, and the assumed t i m i n g e r r o r was normally .05 s. E x c e p t i o n s are noted i n the d e t a i l e d d i s c u s s i o n below. The Highland V a l l e y data can be f i t t e d r e a s o n a b l y with Figure 5. T r a v e l t i m e s , topography, and geology. Upper: Reduced t r a v e l time curves were determined from l e a s t - s g u a r s s f i t s to the data< Crosses are Highland V a l l e y o b s e r v a t i o n s and squares are data from K a i s e r s hots. Middle: The t o p o g r a p h i c variations along the p r o f i l e were measured on 1:250000 maps, lower: The schematic g e o l o g i c a l c r o s s - s e c t i o n was adapted from Campbell (1973) and Wheeler and G a b r i e l s e (1 972) . I n t r u s i v e s - ^ V o l c a n i c s - WM Sediments and V o l c a n i c Sediments-lys-al Sediments-Hudsonian Basement-EES P a l e o z o i c Sediments-38 CD CD CO LO c o CD C O C\J • V= 7 . 9 3 ± . 0 4 km/s Tj=7.38±.2s —Q-• • • • V= 7.49+.01 km/s ' \ V= 7.3 6 ±.01 km/s \E Tj = 4 . 9 3 ± . 0 4 Tj = 4.42±.03s V=6.11±.03 km/s Tj = .39±.03s V = 6 . 0 4 ± . 0 4 k m / s Tj= .121.05 s 0 450 90 360 180 270 270 180 360 90 0 DISTRNCE (KM) |+ INTERIOR PLATEAUX EASTERN METAMORPHIC BELT PURCELl RMT ROCKY +. T, ANTICLINORIUM I I MOUNTAINS I I fif ? / ' / - ^ ^ ^ ^ £'* '~*^~\ J O k n 40 km 39 a two l a y e r model, although a t h r e e l a y e r v e r s i o n with three t r a v e l time branches i s d i s p l a y e d i n F i g u r e 5. The d i f f e r e n c e i s i n the assumption that the three p c i n t s past 178 km r e p r e s e n t a separate t r a v e l time branch from the f i v e p r e v i o u s p o i n t s . The i n t e r c e p t of the near s u r f a c e c r u s t a l r e f r a c t i o n i s non-zero, but t h i s i s a v e s t i g e of the s y s t e m a t i c s c a t t e r i n the p o i n t s that i s d i s c u s s e d below. The branch has a l e a s t squares apparent v e l o c i t y of 6.G4±.04 km/s. The two l a y e r assumption ( a c t u a l l y one l a y e r and a h a l f - s p a c e ) g i v e s a lower l a y e r v e l o c i t y of 7.35±.05 km/s with an i n t e r c e p t of 4.41±.12 s. ft h o r i z o n t a l l y l a y e r e d model c a l c u l a t i o n y i e l d s a depth of 14.6±1.4 km f o r the i n t e r f a c e . With t h i s v e l o c i t y s t r u c t u r e , a Pn a r r i v a l with apparent v e l o c i t y 7.6 km/s and apparent depth of 30 km, would not be observed as a f i r s t a r r i v a l on a p r o f i l e o f t h i s l e n g t h . I f the three a r r i v a l s past 178 km are i n t e r p r e t e d as a separate branch, then the v e l o c i t i e s and i n t e r c e p t s p l o t t e d i n F i g u r e 5 give a 7.36±.02 km/s l a y e r at a depth of 23.4±1.0 km with a t h i c k n e s s of 6.1+.5 km. The h a l f - s p a c e below has an apparent v e l o c i t y of 7.49±.02 km/s. T h i s can be i n t e r p r e t e d as an upper mantle branch, using the c r i t e r i o n of a s s o c i a t i n g apparent v e l o c i t i e s of 7.5 km/s or over with Pn a r r i v a l s . The K a i s e r t r a v e l time curve has two w e l l d e f i n e d branches p l o t t e d i n Figure 5. The f i r s t has an apparent v e l o c i t y of 6.11±.03 km/s. Because the s i x p o i n t s w i t h i n 70 km of the shot have l e s s s c a t t e r , the i n t e r c e p t , ,39±.03 s. ao was c a l c u l a t e d using c n l y them. The a r r i v a l at the r e c o r d i n g s i t e c l c s e s t to the shot i m p l i e s an average f i r s t l a y e r v e l o c i t y of a.5±.02 km/s with a maximum probable t h i c k n e s s of 1.3±.1 km. The second l a y e r has a t h i c k n e s s of 33.2±1.1 km p u t t i n g the 7.93±.04 km/s h a l f - s p a c e at a depth of about 35 km. I t i s immediately obvious that t h e r e are c o n s i d e r a b l e changes along the p r o f i l e , and that a simple h o r i z o n t a l l y l a y e r e d model i s inadequate. The s i m p l e s t a l t e r n a t i v e i s a d i p p i n g l a y e r model. Using formulae frcm Dcbrin (1 960) , and assuming an average upper c r u s t a l v e l o c i t y cf 6.1 km/s , a model was computed with a mantle v e l o c i t y of 7.7 km/s, and a M - d i s c c n t i n u i t y g e n t l y d i p p i n g 2° to the east from a depth of about 25 km under Highland V a l l e y to a depth cf 37 km under the K a i s e r shot p o i n t . Based on the previous d i s c u s s i o n of the t r a v e l time c u r v e s , the assumption f o r the average c r u s t a l v e l o c i t y may be too low, p a r t i c u l a r l y f c r the Highland V a l l e y three l a y e r model, so t h a t the depth i s l i k e l y t o be g r e a t e r than the one c a l c u l a t e d at t h a t end of the p r o f i l e . The c r u s t a l models d e r i v e d from the f i r s t a r r i v a l data are very vague averages. To extend the i n t e r p r e t a t i o n , second a r r i v a l s and l a t e r phases cn the r e c o r d s e c t i o n were i d e n t i f i e d u s ing ray t r a c i n g and s y n t h e t i c seismogram programs. A delay time approach was f i n a l l y used to separate upper mantle topography from l a t e r a l v a r i a t i o n s i n the upper c r u s t a l v e l o c i t y . The c o n s i d e r a b l e near-source 41 v a r i a t i o n s frcm the c r u s t a l t r a v e l time curves are d e s c r i b e d i n d e t a i l i n the f o l l o w i n g s e c t i o n s . 2. Near Source Crusta 1 P r o f i l e from Highland V a l l e y The c o n c e n t r a t i o n of s i t e s near the Highland V a l l e y shot p o i n t s r e f l e c t s an attempt to get s e i s m i c i n f o r m a t i o n about the l o c a l geology. The averaging nature of a r e f r a c t i o n p r o f i l e and the complexity of the geology makes the e v a l u a t i o n n e c e s s a r i l y q u a l i t a t i v e . F igure 6 d i s p l a y s the near scurce t r a c e s out to 80 km with a 6.04 km/s t r a v e l time curve p l o t t e d . The l e a s t squares i n t e r c e p t of . 12±.05 s can be best e x p l a i n e d as due to v a r y i n g s u r f i c i a l t h i c k n e s s e s of lower v e l o c i t y r o c k s . The near-source f i r s t a r r i v a l s are sharp with f o u r or f i v e c y c l e s i n the f i r s t phase. Bethlehem a r r i v a l s tend to have hig h e r f r e q u e n c i e s of 3 t o 10 Hz while Lcrnex a r r i v a l s are i n the 3 to 7 Hz range. The more r a p i d a t t e n u a t i o n of the higher frequency Bethlehem a r r i v a l s may e x p l a i n an apparent s l i g h t overcompensation of Bethlehem amplitudes frcm the PNT s c a l i n g . The Lornex b l a s t s a l s o generate much l a r g e r R a y l e i g h waves (ground r o l l ) . The s u r f a c e wave a r r i v a l s are o f t e n sharp (C1174, A1374) but they were not w e l l c o r r e l a t e d between t r a c e s , r e s u l t i n g i n the p o o r l y d e f i n e d 3.4 km/s branch i n F i g u r e 6. The t r a c e s are p a i r e d . For example , the r e c o r d s A874 and AS74 were recorded from the Bethlehem and Lcrnex shot F i g u r e 6. Near s o u r c e H i g h l a n d V a l l e y s e c t i o n w i t h t r a v e l time c u r v e s . The f i r s t 6.04 km/s c u r v e i s a n e a r s o u r c e c r u s t a l r e f r a c t i o n . The 3.4 km/s c u r v e through the second a r r i v a l s c o r r e s p o n d s to the s u r f a c e wave (ground r o l l ) p r i m a r i l y produced by Lornex b l a s t s . Shots 8-74 10-74, and 2-75 were Bethlehem s h o t s and 9-74, 1 74, 13-74, and 1-75 were Lornex s h c t s . an p o i n t s r e s p e c t i v e l y , u s i n g t h e same s i t e . The ray paths a r e s i m i l a r near the r e c e i v e r , but they a re v e r y d i f f e r e n t c l o s e to t h e shot p c i n t s . T h e r e f o r e , t h e a p p a r e n t v e l o c i t y between f i r s t a r r i v a l s d e t e c t e d a t the same s i t e from two s e p a r a t e s h o t s i s assumed t o te r e l a t e d t o the g e o l o g y w i t h i n a few k i l o m e t e r s o f the shot p o i n t s , and i s r e l a t i v e l y i n d e p e n d e n t of the l o c a l g e o l o g y of the s i t e . The apparent v e l o c i t i e s between a d j a c e n t s t a t i o n l o c a t i o n s , i f t h e y a re c o n s i s t e n t f o r Lornex and Bethlehem s h o t s s e p a r a t e l y , r e f l e c t l a t e r a l v a r i a t i o n s i n a c o u s t i c p r o p e r t i e s between the s i t e s . U s i n g t h e above a s s u m p t i o n s , r e a s o n a b l e e x p l a n a t i o n s can be found f o r most o f the obs e r v e d t r a v e l t i m e a n o m a l i e s . The d e v i a t i o n s frcm the l e a s t - s q u a r e s t r a v e l time c u r v e a l o n g the near s o u r c e p r o f i l e a r e s m a l l , but i f t h e y a r e c o n s i s t e n t , then some g e o l o g i c a l f e a t u r e may be c o r r e l a t e d w i t h them. The average v e l o c i t y between the f i r s t s i t e , A874 and the Bethlehem mine i s 6.2±.2 km/s w h i l e t h e average v e l o c i t y from A974 t o the Lornex p i t i s 6.7±.2 km/s. The Eethlehem mine i s on the e a s t s i d e of the Bethlehem Phase o f the G u i c h c n Creek B a t h o l i t h ( N o r t h c c t e , 1 9 6 9 ) . The Lornex mine i s on the western m a r g i n , so t h a t t h e r a y paths o f t h e waves t r a v e l l i n g from Lornex b l a s t s go th r o u g h t h i s phase o f the b a t h o l i t h , w h i l e the r a y paths from Bethlehem s h o t s a v o i d i t . The two r a y p a t h s are s i m i l a r t o each o t h e r f o r the r e s t o f t h e i r c o u r s e i n the H i g h l a n d V a l l e y Phase. T h i s i m p l i e s t h a t the Bethlehem Phase near the c e r e zone of t h e , 45 b a t h o l i t h has an average v e l o c i t y of 6.7 km/s, while the surrounding Highland V a l l e y Phase has a v e l o c i t y near 6.1 km/s, the average f o r the I n t e r i o r Plateaux n e a r - s u r f a c e c r u s t . G r a v i t y s t u d i e s o f the b a t h c l i t h seem to c o n f l i c t with t h i s data s i n c e the d e n s i t y g e n e r a l l y decreases toward the core zone (Ager et al.,1973). The changing azimuths of s t a t i o n s f a r t h e r away from the shot l o c a t i o n s r e s u l t i n s m a l l v a r i a t i o n s i n the apparent v e l o c i t i e s between Bethlehem and Lornex a r r i v a l s at the same s i t e s . D i f f e r e n t p r o p o r t i o n s of Lornex ray paths are i n the Bethlehem Phase f o r d i f f e r e n t azimuths. T h i s c h a r a c t e r i s t i c can be observed as f a r as 55 km from the sources. The a r r i v a l s C874 and C974 were i n the outer "Hybrid" zone of the b a t h o l i t h and suggest t h a t most of the c u t e r phases have v e l o c i t i e s near 6.0 km/s. The times a t B874 and B974 are l a t e r e l a t i v e to the t r a v e l time curve, perhaps caused by a l a t e r a l low v e l o c i t y zone at the outer margin of the b a t h c l i t h . However, the s i t e was a c t u a l l y o f f of the b a t h c l i t h i c outcrop, on u n c o n s o l i d a t e d sediments of unknown t h i c k n e s s t h a t may have delayed the a r r i v a l . The s t a t i o n s from A1074 to B1174 are l o c a t e d cn the N i c o l a Group of v o l c a n i c s . The s c a t t e r e d a r r i v a l times appear to r e f l e c t an inhomogeneous zone, with v e l o c i t i e s near 6.0 km/s. Unknown t h i c k n e s s e s of g l a c i a l d r i f t miqht make the a r r i v a l s at C1074 and C1174 appear l a t e , thus exaggerating the apparent magnitude of the inhomcgeneity. The a r r i v a l s at A1374 and C275 suggest t h a t , although 46 the formations between them are very inhomogeneous, the average 6.0 km/s v e l o c i t y i s w e l l determined. The l a t e a r r i v a l at C1374 could be a t t r i b u t e d to the u n c o n s o l i d a t e d ' sediments cn which the s i t e was l o c a t e d , or i t may r e f l e c t f u r t h e r inhomcgeneity i n the N i c o l a Group, presumably u n d e r l y i n g the d e t r i t u s . The a r r i v a l s at A275 and A175 are .6 s l a t e . The t r a c e s are very " r i n g y , " probably due to a c o u s t i c q u a l i t i e s of the s i t e , but there i s no reasonable e x p l a n a t i o n on s e i s m i c grounds f o r the delay. However, due to inadequate mapping, t h e r e i s some doubt as to the exact l o c a t i o n of the s i t e , so that these t r a c e s were as s i g n e d 3 km e r r o r s and were weighted a c c o r d i n g l y i n the l e a s t sguares c a l c u l a t i o n s . An a r r i v a l at -.5 s on A175 appears to c o r r e l a t e with energy cn t r a c e s c l o s e r to the s h o t s . T h i s a r r i v a l on A175 i s probably due to an u n i d e n t i f i e d source net r e l a t e d to the Highland V a l l e y shots, and the apparent c o o r e l a t i c n s are erroneous s i n c e they are only observed on the n o i s i e s t t r a c e s . The c r u s t a l a r r i v a l s at d i s t a n c e s g r e a t e r than 80 km are d i s p l a y e d i n F i g u r e 10 (page 59). The a r r i v a l at A1275 i n F i g u r e 10 i s e a r l y . T h i s i s a very unusual t r a c e with i t s high frequency l a r g e amplitude l a t e r a r r i v a l s , and low amplitude c r u s t a l phase. The next t r a c e s , E475 and C475, c o n f i r m an average c r u s t a l v e l o c i t y of 6.04 km/s out to 120 km. East 120 km, the c r u s t a l phase i s e i t h e r delayed or s e v e r e l y a t t e n u a t e d , s i n c e the observed a r r i v a l s a t A775 and B875 are l a t e . T h i s may be due to a major l a t e r a l 47 g e o l o g i c a l boundary c o r r e l a t e d with the Okanagan V a l l e y , which i s l o c a t e d at about 125 km. 3• Near Source C r u s t a l P r o f i l e from K a i s e r The i n t e r p r e t a t i o n of the near source a r r i v a l s of the K a i s e r p r o f i l e p r e s e n t s a more t r a c t a b l e problem than t h a t of the Highland V a l l e y p r o f i l e . There i s c o n s i d e r a b l e upper c r u s t a l g e o p h y s i c a l i n f o r m a t i o n over at l e a s t the f i r s t 80 km. Although they are very complex, the g e o l o g i c a l s t r u c t u r e s are l e s s heterogeneous than those of the I n t e r i o r Plateaux. A l s o , they have a more obvious g e o p h y s i c a l e x p r e s s i o n , that i s , g r e a t e r d e n s i t y , a c o u s t i c and magnetic c o n t r a s t s . The p r e v i o u s l y d e s c r i b e d 6 .1 km/s c r u s t a l r e f r a c t i o n i s very c o n s i s t e n t f o r the f i r s t 80 km on the K a i s e r s e c t i o n i n F i g u r e 8. A gradual i n c r e a s e i n amplitude with very sharp 2 to 4 Hz a r r i v a l s i s the g e n e r a l p a t t e r n . However, the t r a c e j u s t past 80 km, A 1 3 7 5 , has an anomalous f i r s t a r r i v a l time and amplitude. The a r r i v a l time at A1375 i s approximately one second e a r l y . The c r u s t a l phase a r r i v a l times of t r a c e s past 85 km are s c a t t e r e d , but are roughly along the 6 .1 km/s l i n e . The only reasonable model f o r the e a r l y a r r i v a l on A1375 would be an abrupt l a t e r a l upper c r u s t a l v e l o c i t y i n c r e a s e . T h i s i s not r e f l e c t e d i n a r r i v a l s at g r e a t e r d i s t a n c e s . As w e l l , A1375 i s on the west margin of the Pocky Mountain Trench and 48 the work of B a l l y et al.(1966) suggests t h a t a v e l o c i t y decrease i n t h i s area i s more l i k e l y . T h e r e f o r e , the a r r i v a l i s probably a s e i s m i c event u n r e l a t e d to the timed b l a s t . T h i s i s q u i t e probable s i n c e a number of other r e c o r d i n g s experienced i n t e r f e r e n c e frcm background s e i s m i c events. The a t t e n u a t i o n of a r r i v a l s a f t e r the trench i s r e a l . The c r u s t a l phases beyond 80 km are very low amplitude and emergent and the t r a v e l times are s c a t t e r e d around the 6. 1 km/s l i n e . A1675 has a c r u s t a l a r r i v a l l a t e by .1 s, r e f l e c t i n g the lower v e l o c i t y P r o t e r o z o i c sediments i n the P u r c e l l s . The f i r s t a r r i v a l at A574 i s .2 s e a r l y . T h i s c o u l d be e x p l a i n e d by i n a c c u r a t e s i t e l o c a t i o n , or by l o c a l high v e l o c i t y P a l e o z o i c carbonates. I t i s i n t e r e s t i n g to note that the 6.5 km/s basement at a depth of 8 km at K a i s e r could be extended to the west as i n B a l l y e t a l . ( 1 9 6 6 ) . . with a westward s l o p e of 2°, t h i s l a y e r would produce a f i r s t a r r i v a l branch with an apparent v e l o c i t y s l i g h t l y l e s s than 6.5 km/s at about 115 km from the K a i s e r shot p o i n t (Dobrin,1960). The A574 e a r l y a r r i v a l i s a t an a p p r o p r i a t e d i s t a n c e . However, t h i s i n t e r p r e t a t i o n i s u n l i k e l y s i n c e a r r i v a l s at g r e a t e r d i s t a n c e s do not show s i m i l a r c h a r a c t e r i s t i c s , and th e r e are no cor r e s p o n d i n g second a r r i v a l s . The f i r s t a r r i v a l s i n f o u r t r a c e s from E774 to C173 are high frequency very emergent• phases.. E774 and A173 agree w e l l with the 6.1 km/s l i n e . The t r a c e B1675, which appears to be of lower frequency because of severe d i g i t a l 49 f i l t e r i n g , has a a r r i v a l time .3 s l a t e . However, i t was very noisy with an u n c e r t a i n pick of the a r r i v a l . The upper c r u s t a l phase at C173 may have been missed because i t was belcw the n o i s e l e v e l . In support of t h i s , the f i r s t a r r i v a l picked f o r C173 was abrupt, while the a r r i v a l a t A173, 8 km nearer the shot, was very emergent, suggesting t h a t the c o r r e c t f i r s t a r r i v a l time f o r C173 was not picked. The c r u s t a l model needed t o e x p l a i n the kinematic c h a r a c t e r i s t i c s of t h i s p r o f i l e i s a simple 6.1 km/s b l c c k with s m a l l i n h c m o g e n e i t i e s . However, the dynamic c h a r a c t e r i s t i c s , s p e c i f i c a l l y the amplitude a t t e n u a t i o n beyond 80 km, n e c e s s i t a t e a more complex s o l u t i o n . Using the r e s u l t s of B a l l y et a l . (1 966), the average upper c r u s t a l model i n F i g u r e 7 was s y n t h e s i z e d . The 6.1 km/s l a y e r i s composed of P a l e o z o i c s t r a t a . The u n d e r l y i n g low v e l o c i t y P r o t e r o z o i c recks have an unknown extent. The c r y s t a l l i n e basement v e l o c i t y of 6.5 km/s was taken from a study done 100 km to the north by Chandra and dimming (1972). The g e o l o g i c a l d i s c o n t i n u i t y at the Rocky Mountain Trench c o u l d attenuate c r u s t a l amplitudes using any number of reasonable geometries f o r the s t r u c t u r e . F i g u r e 7. Schematic of near source K a i s e r s e i s m i c s t r u c t u r e . I t i s a c o m p i l a t i o n from B a l l y et a l . (1966)-and i s not d e f i n e d by the data set of t h i s study. The p o o r l y determined d i s c o n t i n u i t y at the Rocky Mountain Trench and the sedimentary low v e l o c i t y zone probably c o n t r i b u t e to the low amplitudes observed on the K a i s e r r e c o r d s e c t i o n beyond 80 km. 15km 52 4 • S Y n t h e t i c Seismograms S y n t h e t i c seismogram computaticns o f f e r a method of v e r i f y i n g s e i s m i c models. Phases mere complex than the c r i t i c a l r e f r a c t i o n s that appear as f i r s t a r r i v a l s can be i n c l u d e d i n the i n t e r p r e t a t i o n . However, no g e n e r a l l y a p p l i c a b l e program i s a v a i l a b l e to compute the s e i s m i c response of a l a t e r a l l y heterogeneous medium. T h e r e f o r e , the computed s y n t h e t i c s c o r r e s p o n d i n g to the r e c o r d s e c t i o n s of the present study are u s e f u l only as a g e n e r a l i n d i c a t i o n of the c o r r e c t n e s s of the i n t e r p r e t a t i o n . The models can not be t r e a t e d as d e f i n i t i v e . The D i s c Ray Theory (DBT) method of computation of the s y n t h e t i c seismograms i s d e s c r i b e d by Wiggins (1976). Chapman (1976) has provided a t h e o r e t i c a l d e r i v a t i o n of DRT. The program used was the HRGLTZ r o u t i n e developed by Wiggins. Besides c o n s t r a i n i n g the model to t h a t of l a t e r a l l y homogeneous media, the computational procedure a l s o has d i f f i c u l t y with models t h a t have t h i c k , homogeneous l a y e r s with l a r g e v e l o c i t y c o n t r a s t s . The c o r r e s p o n d i n g head wave amplitudes are exaggerated. T h i s problem can be o b v i a t e d by using the more expensive but exact G e n e r a l i z e d Ray Theory (Wiggins and Helmberger,1974). For the present study, the D i s c Ray Theory approach was used s i n c e only the i d e n t i f i c a t i o n of phases and a s u g g e s t i o n of amplitude trends was expected. The output from the HRGLTZ r o u t i n e i n c l u d e s t r a v e l time 53 curves and s y n t h e t i c seismograms. F i g u r e s 8 and 10 are the K a i s e r and Highland V a l l e y r e c o r d s e c t i o n s , r e s p e c t i v e l y , with the t r a v e l time curves f o r the models i n F i g u r e s 9 and 11 superimposed. F i g u r e s 9 and 11 a l s o i n c l u d e the c c r r e s p c n d i n g computed seismograms. Numerous models were computed: those d i s p l a y e d are the s i m p l e s t , and they demonstrate most of the d i f f i c u l t i e s . The i n t e r p r e t a t i o n of the K a i s e r r e c o r d s e c t i o n i s more complex than the simple t r a v e l time model p r e v i o u s l y d e s c r i b e d . The major change i s the a d d i t i o n cf a 9 km t h i c k 7.05 km/s i n t e r m e d i a t e l a y e r at a depth of 29 km. The wide angle r e f l e c t i o n s from t h i s l a y e r match the l a r g e amplitude phases about 1 s a f t e r the Pn a r r i v a l cn B674, A273, and C273. They c o r r e l a t e w e l l with a r r i v a l s beyond 120 km. The i n t e r f e r e n c e e f f e c t near 125 km, due to r e f l e c t i o n s and r e f r a c t i o n s from the mantle and the i n t e r m e d i a t e l a y e r , produce very l a r g e amplitudes on the s y n t h e t i c s , c o r r e s p o n d i n g with the o b s e r v a t i o n s on B774, A2375, and B1675. The lower amplitudes at d i s t a n c e s l e s s than 120 km are supported by the CST c a l c u l a t i o n s as w e l l . The computed upper c r u s t a l r e f r a c t i o n branch and the r e f l e c t i o n branch frcm the i n t e r m e d i a t e l a y e r converge at the upper r i g h t . There i s a g e n e r a l l y good c o r r e l a t i o n with s e i s m i c energy along these l i n e s out to 440 km. However, the amplitudes computed are f a r too l a r g e . T h i s would be expected from t h i s model, d e s p i t e the problems with the DPT method. fln attempt to use low v e l o c i t y zones or v e l o c i t y g r a d i e n t s to Figure 8. K a i s e r s e c t i o n of Figure 2 with t r a v e l time curves. The t r a v e l time curves were c a l c u l a t e d from the v e l o c i t y - d e p t h -nodel g i v e n i n F i g u r e 9 using the program HRGLTZ. D I S T A N C E (KM) F i g u r e 9. S y n t h e t i c seismogram s e c t i o n and v e l o c i t y model f o r K a i s e r p r o f i l e . In comparison with F i g u r e 8, the amplitudes of the n e a r - s u r f a c e c r u s t a l phase and the wide angle r e f l e c t i o n from the 7.0 km/s l a y e r are e x c e s s i v e . T - D / 8 . 0 (SEC) 58 reduce t h e s e a m p l i t u d e s seems f u t i l e , s i n c e the most prominent c r u s t a l a m p l i t u d e change at A1375 near t h e Rocky Mountain Trench i s c e r t a i n l y r e l a t e d t o l a t e r a l changes. There i s e v i d e n c e f o r a c r u s t a l low v e l o c i t y zone i n t h e d i s a p p e a r a n c e or d e l a y c f the c r u s t a l phase on C173. However, w i t h the p r e s e n t d a t a s e t , t h i s complex a r e a on t h e r e c o r d s e c t i o n cannot be r e s o l v e d . The H i g h l a n d V a l l e y p r o f i l e was more d i f f i c u l t t c model than the K a i s e r p r o f i l e . A f i r s t a p p r o x i m a t i o n p r o v i d e d by t h e s i m p l e model de t e r m i n e d from t h e f i r s t a r r i v a l d a ta p r e v i o u s l y d e s c r i b e d was used t c produce t h e s y n t h e t i c s e c t i o n i n F i g u r e 11. The f i t o f the c o r r e s p o n d i n g t r a v e l time c u r v e t o the a c t u a l d a t a i s d i s p l a y e d i n F i g u r e 10. At d i s t a n c e s beycnd 90 km, t h e H i g h l a n d V a l l e y p r o f i l e has l a r g e a m p l i t u d e phases a r r i v i n g a t about 5.5 s. They are e s p e c i a l l y e v i d e n t on A1275 and B475. These p r o b a b l y c o r r e s p o n d t o p o s t - c r i t i c a l c o n s t r u c t i v e i n t e r f e r e n c e between r e f l e c t e d and c r i t i c a l l y r e f r a c t e d phases from t h e deep c r u s t a l i n t e r f a c e (Cerveny, 1966). A p p a r e n t l y the sub-c r i t i c a l r e f l e c t i o n s a r e o f v e r y s m a l l a m p l i t u d e , s u g g e s t i n g an a b r u p t but not f i r s t o r d e r i n t e r f a c e ( B r a i l e and S m i t h , 1975). S i n c e t h e s y n t h e t i c seismogram program HRGLTZ w i l l have the same d i f f i c u l t i e s w i t h the model d e p i c t e d i n F i g u r e 9 as was p r e v i o u s l y m e n t i o n e d , a comparison o f a m p l i t u d e s i s d i f f i c u l t . The e x c e s s i v e head wave a m p l i t u d e s t h a t the program p r e d i c t s a t l a r g e d i s t a n c e s may be e r r o n e o u s . However, s e v e r a l o b v i o u s s h o r t c o m i n g s o f the' model can be 59 Fi g u r e 10. Highland V a l l e y s e c t i o n o f F i g u r e 3 with t r a v e l time curves. The t r a v e l time curves were c a l c u l a t e d from the v e l o c i t y - d e p t h model i n Figu r e 11, The l a c k of d e f i n i t i o n o f the three l a y e r model i s p a r t i c u l a r l y e v i d e n t . The model i s a l s o u n s a t i s f a c t o r y i n t h a t the upper c r u s t a l r e f r a c t i o n and lower c r u s t a l wide angle r e f l e c t i o n branches do not c o n s i s t e n t l y c o r r e l a t e with the l a r g e amplitude a r r i v a l s appearing past 150 km. D I S T R N C E (KM) F i g u r e 11. S y n t h e t i c seismogram s e c t i o n and v e l o c i t y model of Highland V a l l e y p r o f i l e . Although the g e n e r a l l y poor f i t of the amplitudes to Figure 10 can be improved, many of the most reasonable a l t e r n a t i v e s could not be modelled by DPT. 39 63 v e r i f i e d . The e x i s t e n c e of the i n t e r f a c e at 30 km i s tenuous. A two-layer model g i v e s s i m i l a r r e s u l t s . The sharp phases a r r i v i n g at approximately 5 s on A1275 and C475 and showing c o r r e l a t i o n s on C275 and C1275 have no e x p r e s s i o n i n the model. Most i m p o r t a n t l y , t h e r e are unaccounted sharp phases a r r i v i n g at 7 s and l a t e r on C1075, A1075, A2175 and l e s s o b v i o u s l y on C2175 and A2075. They a r r i v e about 2 s a f t e r the f i r s t a r r i v a l , and a p p a r e n t l y become emergent a f t e r 220 km. I t i s a l s o a f t e r t h i s d i s t a n c e t h a t f i r s t a r r i v a l data become too i n d i s t i c n t to p i c k . Although the a r r i v a l s c o r r e l a t e g e n e r a l l y with the near s u r f a c e c r u s t a l r e f r a c t i o n and the wide angle r e f l e c t i o n frcm the deep c r u s t a l l a y e r , the agreement i s i n c o n s i s t e n t . A f t e r 220 km, the a r r i v a l s are e a r l i e r than the t r a v e l time curve p r e d i c t s f o r e i t h e r phase. T h i s e f f e c t may be due to l a t e r a l changes, but the appearance of the s e c t i o n suggests a deep c r u s t a l low v e l o c i t y zone. The l a r g e a r r i v a l s would correspond to wide angle r e f l e c t i o n s from the top c f the low v e l o c i t y zone. T h i s h y p o t h e s i s i s u n tested, but the G e n e r a l i z e d Ray Theory s y n t h e t i c seismogram programs w i l l be a p p l i e d to t h i s problem i n f u t u r e s t u d i e s . The present study does not d e f i n e the deep s t r u c t u r e i n the d i s t a n c e range of 80 to 180 km cn the Highland V a l l e y p r o f i l e as w e l l as might be accomplished from the data. Perhaps, with more s o p h i s t i c a t e d i n t e r p r e t a t i o n t e c h n i g u e s and a d d i t i o n a l geo'physical c o n t r o l , the i n t e r p r e t a t i o n can 64 be improved. However, i t i s apparent from s y n t h e t i c m o d e l l i n q t h a t t h e r e may be a high v e l o c i t y deep c r u s t a l l a y e r between 80 and 2C0 km from both shot p o i n t s . I t i s s h a l l o w e r , probably t h i c k e r , and of higher apparent v e l o c i t y at the Highland V a l l e y end of the p r o f i l e than at the K a i s e r end (assuming t h a t the Highland V a l l e y deep c r u s t a l a r r i v a l s are not Pn phases). In t h i s i n t e r p r e t a t i o n , the average c r u s t a l v e l o c i t y would i n c r e a s e towards the west from K a i s e r . A low v e l o c i t y zone i n c l u d e d i n the Highland V a l l e y model would net a l t e r t h i s s i t u a t i o n . Since the K a i s e r and Highland V a l l e y i n t e r p r e t a t i o n s d i f f e r c o n s i d e r a b l y , the c r u s t a l s t r u c t u r e s determined from the s y n t h e t i c s assuming l a t e r a l homogeneity are not g e n e r a l l y v a l i d . 5. l e a s t - S q u a r e s Delay Times The obvious l a t e r a l changes a l c n g the p r o f i l e made a term-term method a t t r a c t i v e f o r i n t e r p r e t i n g the Pn f i r s t a r r i v a l s . A s i m p l i f i e d v e r s i o n of the "Delay-Time-Function" method d e s c r i b e d by F o r s y t h et a l . (1974) was used. A d e l a y -time s u r f a c e composed of l i n e a r and F o u r i e r terms (as a f u n c t i o n of p o s i t i o n ) was f i t t e d to the t r a v e l time data using l e a s t - s g u a r e s . The f i r s t f i t used a p r e s e t average o f f s e t d i s t a n c e and lower l a y e r v e l o c i t y . In subsequent i t e r a t i o n s , an o f f s e t d i s t a n c e p r o p o r t i o n a l to the time-term was a p p l i e d and the lower l a y e r v e l o c i t y was updated. T h i s method r e q u i r e s t h a t there not be a high c o r r e l a t i o n between 65 s h o t / r e c e i v e r d i s t a n c e and p o s i t i o n ( M o r r i s , 1972). A l s o , the upper l a y e r average v e l o c i t y should net change s i n c e t h i s a f f e c t s the correspondence between the delay times and the depth to the r e f r a c t i n g i n t e r f a c e . Because only three u n c e r t a i n Pn t r a v e l times from the Highland V a l l e y sources are a v a i l a b l e , the f i r s t reguirement i s very n e a r l y u n f u l f i l l e d . The d i f f e r e n t c r u s t a l s t r u c t u r e s p r e v i o u s l y determined f o r o p p o s i t e ends c f the p r o f i l e may make the time terms only i n d i r e c t l y i n d i c a t i v e of mantle depths. The average c r u s t a l v e l o c i t y a t the Highland V a l l e y end, as suggested i n the model c f F i g u r e 11, i s near 6.5 km/s. I t i s near 6.3 km/s f o r the Kaiser model. A range of average v e l o c i t i e s were used to f i t the d a t a , but h i g h e r v e l o c i t i e s gave a lower standard d e v i a t i o n f o r the s o l u t i o n s . T h e r e f o r e , a 6.5 km/s average upper c r u s t a l v e l o c i t y was assumed. The r e s u l t s cf c o n s t r a i n i n g the delay-time s u r f a c e t o a d i p p i n g plane r e s u l t e d i n the t h i r d i t e r a t i o n s o l u t i o n given i n F i g u r e 12a. The t r a v e l time o b s e r v a t i o n corresponding to B273 (Figure 8) was not used i n the f i n a l delay time s o l u t i o n s because of i t s l a r g e r e s i d u a l i n the p r e l i m i n a r y work. The l e a s t sguares mantle v e l o c i t y was 7.82±.04 km/s with a standard d e v i a t i o n of .14 s f o r the s o l u t i o n . There i s an apparent o s c i l l a t i o n , with a 165 km wave l e n g t h , of the o b s e r v a t i o n s about the l i n e . An a d d i t i o n a l F o u r i e r term of t h i s wavelength was i n c l u d e d i n the s o l u t i o n of F i g u r e 12b. The l e a s t squares mantle v e l o c i t y f o r t h i s s o l u t i o n , which had a s t a n d a r d d e v i a t i o n F i g u r e 12a. Delay time s o l u t i o n f o r a plane. The Highland V a l l e y and K a i s e r shot p o i n t s are l o c a t e d at -225 and 225 km. Crosses (Highland V a l l e y ) and squares (Kaiser) denote o b s e r v a t i o n s from each source. The average c r u s t a l v e l o c i t y was assumed to be 6.5 km/s. T h i s i s a t h i r d i t e r a t i o n r e s u l t i n g i n a l e a s t - s q u a r e s r e f r a c t o r v e l o c i t y of 7,82±.04 km/s. The standard d e v i a t i o n of the s o l u t i o n i s .1U s. Note the apparent o s c i l l a t i o n (of one c y c l e ) with a 165 km wave l e n g t h . F i g u r e 12b. Delay time s o l u t i o n with one F o u r i e r term. The assumed average c r u s t a l v e l o c i t y was 6.5 km/s, g i v i n g a t h i r d i t e r a t i o n s o l u t i o n with a .08 s standard d e v i a t i o n . The c a l c u l a t e d r e f r a c t o r v e l o c i t y was 7.80+.03 km/s. Note the disagreement i n the s l o p e s of the Highland V a l l e y and K a i s e r data set about the s o l u t i o n . 70 o f .08 s, was 7.80±.03 km/s. The peak to peak a m p l i t u d e of the o s c i l l a t i o n was a p p r o x i m a t e l y .5 s. The c a l c u l a t e d d e l a y t i m e s range frcm 3.0 to 3.6 s. I t i s i m p o r t a n t t o note t h a t t h e s o l u t i o n i s v a l i d c n l y where data p o i n t s e x i s t . The i n t e r p r e t a t i o n o f the d e l a y t i m e s o l u t i o n s i n v o l v e s the s e p a r a t i o n o f c r u s t a l v e l o c i t y v a r i a t i o n from mantle topography. L a t e r a l v e l o c i t y changes i n the upper mantle a r e a l s o p o s s i b l e , but the s t a b i l i t y o f t h e d e l a y time s o l u t i o n s f o r a 7.8 km/s v e l o c i t y s u g g e s t s t h a t t h i s i s not a major c o n s i d e r a t i o n . The p r e v i o u s l y d e t e r m i n e d upper c r u s t a l models would r e s u l t i n a d e l a y time i n c r e a s e from H i g h l a n d V a l l e y t o K a i s e r . The magnitude would be from . 2 t o . U s i f t h e r e were no l a t e r a l changes i n the M-d i s c c n t i n u i t y . T h i s would account f o r most of the c o s i n e term of the d e l a y time s o l u t i o n . Assuming t h a t most of the c o s i n e term i s r e l a t e d t o average c r u s t a l v e l o c i t y , t h e n a sudden decrease i n v e l o c i t y a p p a r e n t l y o c c u r s between 0 t o 60 km cn t h e s c a l e o f F i g u r e 12. T h i s c o r r e s p o n d s t o the a r e a from j u s t e a s t of the Arrow Lakes t o Kootenay Lake on F i g u r e 1. Because o f the l a t e r a l v e l o c i t y change, the d e l a y t i me c o n v e r s i o n t o depths i s t o e l a r g e a t t h e K a i s e r end o f the p r o f i l e . T a k i n g the v e l o c i t y v a r i a t i o n s i n t o c o n s i d e r a t i o n i n a s u b j e c t i v e f a s h i o n , , the d e l a y t ime s o l u t i o n i n d i c a t e s a 7.8 km/s M - d i s c o n t i n u i t y d i p p i n g from about 33 km near the H i g h l a n d V a l l e y t o a p c o r l y d e f i n e d 40 km a t the K a i s e r end. 71 The a l t e r n a t i v e would be t o assume t h a t the delay times r e f l e c t e d mantle topography d i r e c t l y . T h i s iray imply t h a t at l e a s t p a r t of the 7.35 km/s t r a v e l time branch i n t e r p r e t e d as being from the lcwer c r u s t i s a c t u a l l y a s s o c i a t e d with c r i t i c a l r e f r a c t i o n s from a s t e e p l y d i p p i n g M - d i s c o n t i n u i t y . In t h i s case, the mantle boundary would di p s t e e p l y tc the east l o c a l l y beneath the r e g i o n adjacent to Ckanagan Lake and the p r e v i o u s l y d e s c r i b e d area between the Arrow l a k e s and Kootenay Lake. T h i s i n t e r p r e t a t i o n i s encouraging s i n c e l a t e r a l changes i n v e l o c i t y dc not seem to compensate f o r a l l o f , t h e s h o r t wavelength c h a r a c t e r of the delay time curve. A l s o , the delay times match w e l l with the delay time s o l u t i o n s determined f o r areas immediately t o the west (Berry and F o r s y t h , 1975). However, as Berry and F o r s y t h (1975) note, the l a c k of improvement of a s o l u t i o n with an i n c r e a s e d number of i t e r a t i o n s , t o g e t h e r with a s y s t e m a t i c disagreement between r e v e r s e d p o i n t s on a d e l a y time curve, suggest t h a t there are s i g n i f i c a n t l a t e r a l average c r u s t a l v e l o c i t y v a r i a t i o n s . Beth c f these i n d i c a t i o n s are evident i n t h i s study. T h e r e f o r e , i t i s l i k e l y t h a t both h o r i z o n t a l v e l o c i t y g r a d i e n t s and r e l a t i v e l y s h o r t wavelength c r u s t - m a n t l e topography are p r e s e n t . 72 6. D i s c u s s i o n The i n t e r p r e t a t i o n of t h i s p r o f i l e as d e s c r i b e d i s i n ge n e r a l agreement with p r e v i o u s s t u d i e s o f the r e g i o n . The primary f e a t u r e i s a 7.8 km/s M - d i s c o n t i n u i t y d i p p i n g t o the e a s t , with an average depth near 35 km. Although the r e s o l u t i o n o f t h i s study i s l i m i t e d , i t does c o n f i r m p r e v i o u s models d e r i v e d from g r a v i t y data (Stacey, 1973) . The near source i n f o r m a t i o n was a l s o not d e f i n i t i v e , a l though i t i n d i c a t e d seme i n t e r e s t i n g f e a t u r e s . The mcst i n t e r e s t i n g r e s u l t s were the short wavelength but very smooth v a r i a t i o n s i n the de l a y time i n t e r p r e t a t i o n , the deep c r u s t a l l a y e r s , and the undeveloped p o s s i b i l i t y of a low v e l o c i t y zone i n t e r p r e t a t i o n f o r the Highland V a l l e y p r o f i l e . A deep c r u s t a l l a y e r from the Ka i s e r data was not s u p r i s i n g s i n c e Chandra and Cumming (1972) suggested a s i m i l a r 7.0 km/s l a y e r immediately to the east of K a i s e r , with a g r a d u a l taper to the west. The t h i c k n e s s c a l c u l a t e d i n t h i s study was g r e a t e r than was p r e v i o u s l y suggested. A l l o w i n g f o r o f f s e t d i s t a n c e s , the l a y e r a p p a r e n t l y e x i s t s a t l e a s t as f a r west as Kootenay Lake. The a r r i v a l s become i n d i s t i n c t a t g r e a t e r d i s t a n c e s , and, c o n s i d e r i n g the other c o m p l i c a t i o n s i n t h i s a r e a , t h i s i s very r e a s o n a b l e . The deep c r u s t a l l a y e r i n the Highland V a l l e y i n t e r p r e t a t i o n i s more tenuous. The p o s s i b i l i t y o f a steep eastward d i p i n the mantle, suggested by the delay time 73 study, c o m p l i c a t e s the problem of s e p a r a t i n g deep c r u s t a l branches from Pn s e c t i o n s of the t r a v e l time curve. A l s o , the data i s of poorer q u a l i t y . From a p r o f i l e d i r e c t e d westward from a shot point approximately 90 km east of the Highland V a l l e y , Berry and F o r s y t h (1975) found an i n t e r m e d i a t e c r u s t a l l a y e r of v e l o c i t y frcm 6.5 to 7.0 km/s ( i n c r e a s i n g with depth). Since i t has not been found elsewhere i n E r i t i s h Columbia, t h i s may i n d i c a t e t h a t such a l a y e r e x i s t s c n l y south of 51°. T h e r e f o r e , the east-west s t r i k i n g upper mantle boundary near t h i s l a t i t u d e t h a t i s d e s c r i b e d i n the G e o p h y s i c a l Review of Chapter I, may have a g e n e r a l e x p r e s s i o n i n the deep c r u s t as w e l l . Because of the g e o l o g i c a l complexity of the C o r d i l l e r a , and because of i t s u n c e r t a i n t e c t o n i c h i s t o r y , a d e f i n i t i v e c o r r e l a t i o n can not be made between the present study and h y p o t h e t i c a l t e c t o n i c models. Eerry and F o r s y t h (1975) e x t e n s i v e l y d i s c u s s e d p o s s i b l e t e c t o n i c i m p l i c a t i o n s of s e i s m i c r e f r a c t i o n i n t e r p r e t a t i o n s i n B r i t i s h Columbia. The t e c t o n i c c o m p l i c a t i o n s t h a t they c o n s i d e r e d can be s i m p l i f i e d by r e l a t i n g g e o p h y s i c a l f e a t u r e s p r i m a r i l y t c s t r u c t u r e s that would have formed s i n c e the Cretaceous. The r e g i o n c o n s i d e r e d i n t h i s study has not undergone subduction or t r a n s c u r r e n t type a c t i v i t y s i n c e then. V e r t i c a l t e c t o n i c s have probably c h a r a c t e r i z e d the deep c r u s t and upper mantle, and i t i s probably t h i s a c t i v i t y t h a t has the g r e a t e s t e f f e c t on present g e o p h y s i c a l parameters. The i n t e r p r e t a t i o n of the o b s e r v a t i o n s using t h i s v i e w p o i n t . 74 r e d u c e s t h e s p e c u l a t i v e p o s s i b i l i t i e s c o n s i d e r a b l y . The C o r d i l l e r a n T h e r m a l Anomaly Zone, which p r o b a b l y i n c l u d e s mcst o f t h e I n t e r i o r P l a t e a u x and a l l c f t h e E a s t e r n M e t a m o r p h i c B e l t and P u r c e l l A n t i c l i n o r i u m , i s p r o b a b l y an e f f e c t o f T e r t i a r y s u t d u c t i o n o f t h e E a s t P a c i f i c p l a t e and t h e F a r a l l o n (now J u a n de Fuca) p l a t e a t t h e l a t i t u d e s c f t h e p r e s e n t s t u d y ( B e r r y e t a l , 1 9 7 1 ; A t w a t e r , 1 9 7 0 ) . The l a t e - M e s o z o i c t h e r m a l e v e n t s may be a s s o c i a t e d w i t h a more c o m p l e x s y s t e m o f i m b r i c a t e h i g h a n g l e s u b d u c t i c n z o n e s (Godwin,1975). The r e l a t i v e l y s h a l l o w and lew v e l o c i t y u p p e r m a n t l e b e n e a t h t h e E a s t e r n M e t a r a c r p h i c B e l t may te r e l a t e d t o t h e h e a t i n g and a s s o c i a t e d upward m o b i l i t y o f t h e s e t h e r m a l r e g i m e s . The i n t e n s i t y o f s u r f a c e metamcrphism used as a measure o f l a t e - M e s o z c i c t o r e c e n t anomalous t h e r m a l a c t i v i t y a l l o w s a d i r e c t a s s o c i a t i o n o f t h e d e l a y t i m e d i s c o n t i n u i t i e s w i t h t h e r m a l b o u n d a r i e s . The most i n t e n s e metamorphism a l o n g t h e l i n e o f t h e H i g h l a n d V a l l e y t o K a i s e r p r o f i l e o c c u r s between Okanagan Lake and t h e Arrow L a k e s . The r e g i o n between the Arrow L a k e s and K o o t e n a y Lake e x p e r i e n c e d somewhat l e s s s e v e r e metamorphism, w h i l e t h e P u r c e l l M o u n t a i n s were o n l y m i l d l y a f f e c t e d . T h e r e f o r e , e a s t o f Okanagan L a k e , the i n c r e a s i n g d e l a y t i m e s a r e w e l l c o r r e l a t e d w i t h d e c r e a s i n g metamcrphism. The l a t e r a l c h a n g e s p r e v i o u s l y d e s c r i b e d i n e i t h e r t h e l o w e r c r u s t o r t h e m a n t l e c o u l d be c o n s i s t e n t w i t h t h i s view. Mechanisms t h a t might e x p l a i n t h e a p p a r e n t c c r r e l a t i c n o f more s e v e r e metamorphism w i t h e i t h e r a h i g h e r 75 average v e l o c i t y i n t h e c r u s t o r a s h a l l o w e r and perhaps l o w e r v e l o c i t y upper mantle a r e h i g h l y s p e c u l a t i v e . The s h a l l o w , h i g h v e l o c i t y l o w e r c r u s t a l l a y e r p o s t u l a t e d beneath t h e west s e c t i o n of the E a s t e r n Metamorphic E e l t c o u l d be formed by a d i f f e r e n t i a t i o n p r o c e s s s u g g e s t e d by R.L. Armstrong ( p e r s o n a l c o m m u n i c a t i o n , 1976). Under i n t e n s e h e a t i n g w i t h p a r t i a l c r f u l l m e l t i n g , t h e h e a v i e r g a b b r o i c r o c k s c o u l d s e p a r a t e downward from t h e l i g h t e r , l o w e r v e l o c i t y g r a n i t i c r o c k s which would form the s u r f a c e l a y e r . I f the degree o f t h i s a c t i v i t y was r e l a t e d t o t h e r a t e of u p l i f t , t h e n s u r f a c e e r o s i o n and l a t e r a l movement of the near s u r f a c e l a y e r s c o u l d a c c o m p l i s h a net l a t e r a l change i n average c r u s t a l v e l o c i t y and, presumably, d e n s i t y ( P r i c e and Mountjoy,1970). However, t h i s d e n s i t y i n c r e a s e c o n t r a d i c t s the f i n d i n g s o f S t a c e y (1973). The o n l y o t h e r e v i d e n c e i n the E a s t e r n Metamorphic B e l t f o r a deep c r u s t a l or upper mantle boundary a s s o c i a t e d w i t h t h e r m a l e f f e c t s was t h e c o n d u c t i v e , h y d r a t e d lower c r u s t proposed by Caner (1971). The depth of 10 t o 15 km, l a t e r m o d i f i e d t o 20 t o 40 km, c o u l d be i d e n t i f i e d w i t h e i t h e r a c r u s t a l anomaly i n t h e former c a s e , or a deep c r u s t / u p p e r mantle anomaly i n the l a t t e r c a s e . A l s o , t h e magnetic t r a n s i t i o n zone marking the e a s t e r n boundary of the c o n d u c t i v e l a y e r i s near Kootenay Lake, t h e e a s t e r n boundary of t h e r a p i d i n c r e a s e i n the d e l a y times. These o b s e r v a t i o n s are c e r t a i n l y r e l a t e d , a l t h o u g h the p r e c i s e n a t u r e o f t h e a s s o c i a t i o n i s obscured by poor r e s o l u t i o n . 76 Anomalous b e h a v i o u r i n t h e u p p e r m a n t l e would a l s o be e x p e c t e d n e a r major l a t e r a l t h e r m a l b o u n d a r i e s . W i c k e n s (1976) has s u g g e s t e d t h a t t h e lew upper m a n t l e v e l o c i t y d e t e r m i n e d w i t h i n t h e C o r d i l l e r a n T h e r m a l Anomaly Zcne i n d i c a t e s t h a t t h e G u t e n b u r g low v e l o c i t y z c n e i s a t c r n e a r t h e base o f t h e c r u s t . S i n c e s m a l l e r s c a l e t h e r m a l f e a t u r e s o b s e r v e d a t t h e s u r f a c e p r o b a b l y have t h e i r o r i g i n s b e l c w t h e M - d i s c c n t i n u i t y as w e l l , t h e d e p t h t o t h i s a l r e a d y a n o malous m a n t l e b o u n d a r y may v a r y l a t e r a l l y i n a f a s h i o n a n a l o g o u s t o t h e met a m o r p h i c v a r i a t i o n s i n t h e s u r f a c e f e a t u r e s . W h i l e t h e g e n e r a l f e a t u r e s o f t h e deep c r u s t and m a n t l e o f t h e c e n t r a l C o r d i l l e r a p r o b a b l y r e l a t e t c l a t e - M e s c z c i c t o r e c e n t e v e n t s , t h e d e t a i l s may have a much o l d e r h i s t o r y . The p o s s i b l e i n c r e a s e i n a v e r a g e c r u s t a l v e l o c i t y between K o o t e n a y Lake and t h e Arrow L a k e s c o u l d a l s c be e x p l a i n e d i n t e r m s c f h o r i z o n t a l t e c t o n i c novements. I . Duncan ( p e r s o n a l c o m m u n i c a t i o n , 1977) s u g g e s t s t h a t t h e E a s t e r n M e t a m o r p h i c B e l t west c f t h e Arrow L a k e s was a s e p a r a t e c r u s t a l b l c c k e a r l y i n t h e P a l e o z o i c , a l t h o u g h i t s p o s i t i o n had n e t c h a n g e d r e l a t i v e t o t h e c r a t o n , p r o b a b l y s i n c e t h e P r o t e r o z o i c . When s u c h a n c i e n t l a t e r a l v a r i a t i o n s a r e t a k e n i n t o a c c o u n t , a much b e t t e r u n d e r s t a n d i n g o f t h e g e o p h y s i c a l and g e o l o g i c a l s i t u a t i o n t h a n h as been a c c o m p l i s h e d i s n e c e s s a r y t o r e l a t e g e o p h y s i c a l p a r a m e t e r s t o t h e p r e -M e s o z o i c g e o l o g y and t e c t o n i c s . 77 7. C o n c l u s i o n s 1. In o r d e r t o o b t a i n u p p e r c r u s t a l r e s o l u t i o n i n h e t e r o g e n e o u s a r e a s s u c h as t h e I n t e r i o r P l a t e a u x an a r e a l p l a n f o r t h e e x p e r i m e n t ( s u c h a s f a n p r o f i l i n g ) c o u l d be u s e d w i t h a s t a t i o n s p a c i n g l e s s t h a n 1 km. The p r e s e n t s t u d y s u g g e s t s t h a t i n t e r e s t i n g v e l o c i t y c o n t r a s t s do e x i s t ; f o r example i n t h e h i g h v e l o c i t y c o r e zone o f t h e G u i c h c n C r e e k B a t h o l i t h . The K a i s e r p r o f i l e r e s u l t s show t h a t t h e Rocky M o u n t a i n T r e n c h i s a major l a t e r a l b o u n d a r y , b u t w i t h o u t r e v e r s e d s e i s m i c c o n t r o l , t h e n a t u r e o f t h i s d i s c o n t i n u i t y i s s p e c u l a t i v e . I t may be t h a t r e f r a c t i o n methods do not have t h e n e c e s s a r y r e s o l u t i o n t o d e l i n e a t e t h i s f e a t u r e . 2. T h e r e a r e major l a t e r a l c h a n g e s , i n b o t h t h e a v e r a g e c r u s t a l v e l o c i t y and t h e m a n t l e d e p t h , a t s h o r t w a v e l e n g t h s i n t h e E a s t e r n M e t a m o r p h i c B e l t . 3. B e s i d e s p o s s i b l e s h o r t e r wave l e n g t h d e p t h v a r i a t i o n s , t h e upper m a n t l e o f v e l o c i t y c l o s e to 7.8 km/s g e n e r a l l y d i p s t o t h e e a s t from an a p p r o x i m a t e d e p t h o f 33 km n e a r t h e H i g h l a n d V a l l e y t o a b o u t 42 km j u s t t o t h e west o f t h e K a i s e r s h o t p o i n t . 4. The s h o r t w a v e l e n g t h d e l a y t i m e a n o m a l i e s c a n be c o r r e l a t e d w i t h t h e t h e r m a l h i s t o r y and v e r t i c a l t e c t o n i c e v e n t s s i n c e t h e J u r a s s i c . 5. T h e r e i s s t r o n g e v i d e n c e f o r an i n t e r m e d i a t e c r u s t a l 78 l a y e r o f v e l o c i t y 7.05 km/s, d e p t h 29 km, and t h i c k n e s s 9 km between 100 and 200 km f r c m t h e K a i s e r s h o t p o i n t . Based on t h e i n t e r p r e t a t i o n c f p o o r e r d a t a , a 7.35 km/s l a y e r may e x i s t between 80 and 180 km f r o m t h e H i g h l a n d V a l l e y s h c t p o i n t a t a d e p t h o f 15 t o 24 km and a t h i c k n e s s o f 6 t o 10 km. 6. T h i s s t u d y c o n f i r m s s u g g e s t i o n s by o t h e r s ( B e r r y and F o r s y t h , 1975) t h a t l a t e r a l s t r u c t u r e and lew v e l o c i t y c h a n n e l s c a n o n l y be d e f i n e d w e l l w i t h a s i g n a l - t o - n o i s e r a t i o c f 2 o r b e t t e r and a r e g u l a r s t a t i o n s p a c i n g o f l e s s t h a n 20 km. The u n i g u e n e s s o f an i n t e r p r e t a t i o n c c u l d be t e s t e d by v a r y i n g s h o t p o i n t s a s w e l l a s s t a t i o n l o c a t i o n s a l o n g a p r o f i l e . A number o f s t a t i o n s r e c o r d i n g m u l t i p l e s h o t s t h a t a r e s e p a r a t e d by a t l e a s t t h e a v e r a g e s t a t i o n s p a c i n g would make a d e l a y t i m e a p p r o a c h more v a l i d . F o r t h e i m i t e d i a t e f u t u r e , s e i s m i c e x p e r i m e n t s would be most s u c c e s s f u l i n d e l i n e a t i n g l a t e r a l a n o m a l i e s (which a r e o f t e n t h e most i n t e r e s t i n g and s i g n i f i c a n t f e a t u r e s ) , i f t h e e x p e r i m e n t was a d a p t e d t o t i m e - t e r m a n a l y s i s . R e c e n t work by E a m f o r d ( 1 9 7 6 ) , s u g g e s t s t h a t t i m e - t e r m and p r o f i l i n g a p p r o a c h e s a r e c o m p a t i b l e , p a r t i c u l a r l y i f t h e y a r e d e s i g n e d t o be used i n c o n j u n c t i o n w i t h e a c h o t h e r . 79 L I S T OF REFERENCES Ager,C.A., U l r y c h , T . J . , and M c M i l l a n , H . J . 1973. A g r a v i t y model f o r t h e G u i c h c n C r e e k b a t h o l i t h , s o u t h - c e n t r a l B r i t i s h C o l u m b i a . Can. J . E a r t h S c i . , 10, pp. 920-935. Ahern,T.K. 1975. An c * V O * 6 s t u d y o f w a t e r f l o w i n n a t u r a l snow. U n p u b l . M.Sc. T h e s i s , U n i v . B r i t i s h C o l u m b i a , V a n c o u v e r , B r i t i s h C o l u m b i a . 164 pp. A t w a t e r , T . 1970. I m p l i c a t i o n s o f p l a t e t e c t o n i c s f c r t h e C e n o z c i c t e c t o n i c e v o l u t i o n o f w e s t e r n N o r t h A m e r i c a . E u l l . G e o l . Soc. Am.,81, pp. 3513-3536. B a l l y , A . w . , G o r d y , P . L . , and S t e w a r t , G . A . 1966. S t r u c t u r e , s e i s m i c d a t a and o r o g e n i c e v o l u t i o n o f s o u t h e r n C a n a d i a n Rocky M o u n t a i n s . B u l l . Can. P e t . G e o l . , 14, pp. 337-381. Eamford,D. 1976. MOZAIC t i m e - t e r m a n a l y s i s . Geophys. J . R. a s t r . S o c , 44, pp. 433-446. B e n n e t t , G . T . 1973. A s e i s m i c r e f r a c t i o n s u r v e y a l o n g t h e s o u t h e r n Rocky M o u n t a i n T r e n c h . U n p u b l . M.Sc. T h e s i s , U n i v . E r i t i s h C o l u m b i a , V a n c o u v e r , B r i t i s h C o l u m b i a . 70 pp. B e n n e t t , G . T . , Clowes,B.M., and E l l i s , R . M . 1975. A s e i s m i c r e f r a c t i o n s u r v e y a l o n g t h e s o u t h e r n Rocky M o u n t a i n T r e n c h , Canada. B u l l . S e i s m . Soc. An., 65, pp. 37-54. B e r r y , M . J . , Jacoby,W.R., N i b l e t t , E . S . and S t a c e y , P . A . 1971. A r e v i e w o f g e o p h y s i c a l s t u d i e s i n t h e C a n a d i a n C o r d i l l e r a . Can. J . E a r t h S c i . , 8, pp. 788-801. B e r r y , M . J . and F o r s y t h , D . A . 1975. S t r u c t u r e o f t h e C a n a d i a n C o r d i l l e r a f r o m s e i s m i c r e f r a c t i o n and o t h e r d a t a . Can. J . E a r t h S c i . , 12, pp. 182-208. B l a c k w e l l , D . D . 1969. H e a t - f l o w d e t e r m i n a t i o n s i n t h e n o r t h w e s t e r n U n i t e d S t a t e s . J . Gecphys. R e s . , 74, pp. 992-1006. B r a i l e , L . H . and Smith,R.B. 1975. G u i d e t o t h e i n t e r p r e t a t i o n c f c r u s t a l r e f r a c t i o n p r o f i l e s . G e o p h y s . J . R. a s t r . Soc. , 40, pp. 145-176. 80 C a m f i e l d , P . A . and Gough,D.I. 1975. Anomalies i n d a i l y v a r i a t i o n magnetic, f i e l d s and s t r u c t u r e under t h e n o r t h - w e s t e r n U n i t e d S t a t e s and s o u t h - w e s t e r n Canada. Geophys. J . R. a s t r . S o c , 41, pp. 193-218. Campbell,R.B. 1973. S t r u c t u r a l c r o s s - s e c t i o n and t e c t o n i c model o f the s o u t h e a s t e r n Canadian C c r d i l l e r a . Can. J . E a r t h S c i . , 10, pp. 1607-1620. Caner,B., Auld,D.R., C r a g e r t , H . and C a m f i e l d , P . A . 1971. Geomagnetic d e p t h - s o u n d i n g and c r u s t a l s t r u c t u r e i n western Canada. J . Geophys. Res., 76, pp. 7181-7201. Caner,B. 1971. Q u a n t i t a t i v e i n t e r p r e t a t i o n o f geomagnetic d e p t h - s o u n d i n g d a t a i n w e s t e r n Canada. J . Geophys. Res., 76, pp. 7202-7216. Cerveny,V. 1966. On dynamic p r o p e r t i e s o f r e f l e c t e d and head waves i n the n - l a y e r e d e a r t h ' s c r u s t . Geophys. J . R. a s t r . S o c , 11, pp. 139- 147. Chandra,N.N. and Cumming,G.l. 1972. S e i s m i c r e f r a c t i o n s t u d i e s i n wester n Canada. Can. J . E a r t h S c i . , 9 , p p . 1099-1109. Chapman,CH. 1S76. E x a c t and approximate g e n e r a l i z e d r a y t h e o r y i n v e r t i c a l l y inhomogeneous media. Geophys. J . R. a s t r . S o c , 46, pp. .201-223. Dobrin,M.E. 1960. I n t r o d u c t i o n t o G e o p h y s i c a l P r o s p e c t i n g . M c G r a w - H i l l Beck Co., N.Y. 446 pp. Dr a g e r t , H . 1973. A t r a n s f e r f u n c t i o n a n a l y s i s o f a geomagnetic depth s o u n d i n g p r o f i l e a c r o s s c e n t r a l B r i t i s h Columbia. Can. J . E a r t h S c i . , 10, pp. 1089-1098. F o r s y t h , D . A . , E e r r y , M . J . and E l l i s , R . M . 1974. A r e f r a c t i o n s u r v e y a c r o s s the Canadian C o r d i l l e r a a t 54 N. Can. J . E a r t h S c i . , 11, pp. 533-548. Godwin,C.I. 1975. I m b r i c a t e s u b d u c t i o n zones and t h e i r r e l a t i o n s h i p w i t h upper C r e t a c e o u s t c T e r t i a r y porphyry d e p o s i t s i n the Canadian C c r d i l l e r a . Can. J . E a r t h S c i . , 12, pp. 1362-1378. Haines,G.V., Hannaford,V., and Riddihough,R.P. 1971. Magnetic a n o m a l i e s over B r i t i s h C o l u m b i a and the a d j a c e n t P a c i f i c Ocean. Can. J . E a r t h S c i . , 8, pp. 387-391. 8 1 J e s s o p , A . M . and J u d g e , A . S . 1971. F i v e measurements o f h e a t f l o w i n s o u t h e r n Canada. Can. J . E a r t h S c i . , 8, pp. 711-716. Kanasewich,E.R. 1968. Precambrian r i f t : genesis of s t r a t a bound ore deposits. Science, 161, pp. 1002-1005. I K a n a s e w i c h , E . F . , Clowes,P.M., and McCloughan,C. H. 1969. A b u r i e d P r e c a m b r i a n r i f t i n w e s t e r n Canada. T e c t o n o p h y s i c s , 8, pp. 513-527. K a n a s e w i c h , E . E . 1975. Time Sequence A n a l y s i s i n G e o p h y s i c s . U n i v e r s i t y o f A l b e r t a P r e s s . 364 pp. Law,L.K. and R i d d i h o u g h , R . P . 1971. A g e o g r a p h i c a l r e l a t i o n between g e o m a g n e t i c v a r i a t i o n a n o m a l i e s and t e c t o n i c s . Can. J . E a r t h S c i . , 8, pp. 1094-1106. Leech,G.B. 1965. The Rocky M o u n t a i n T r e n c h , i n : The H c r l d R i f t S y s t e m , G e o l . S u r v . Can. P a p e r 66-14, pp. 307-329. Monger,J.w.H., S o u t h e r , J . G . , and G a t r i e l s e , H . 1972. E v o l u t i o n c f t h e C a n a d i a n C o r d i l l e r a : a p l a t e t e c t o n i c model. Am. J . S c i . , 272, pp. 577-602. M o r r i s , G . B . 1972. D e l a y - t i m e - f u n c t i o n method and i t s a p p l i c a t i o n t o t h e Lake S u p e r i o r r e f r a c t i o n d a t a . J . Geophys. R e s . , 77, pp. 294-314. N o r t h c o t e , K . E . 1969. G e o l o g y and g e c c h r c n o l c g y o f t h e G u i c h c n C r e e k b a t h o l i t h . E.C. Dept. o f Mines and P e t r o l e u m R e s o u r c e s B u l l e t i n . No. 56. P r i c e , R . A . and M o u n t j o y , E . H . 1970. G e o l o g i c s t r u c t u r e o f t h e C a n a d i a n Rocky M o u n t a i n s between Eow and A t h a b a s c a R i v e r s . G e o l . A s s o c . Can., Spec. Pap. 6, pp. 7-26. R e i t z e l , J . S . , Gough,B.I., P o r a t h , H . , and Andersen,C.W. 1970. G e o m a g n e t i c deep s o u n d i n g and upper m a n t l e s t r u c t u r e i n w e s t e r n U n i t e d S t a t e s . Geophys. J . R. a s t r . Soc. 19, pp. 213-235. Spenc€,G. D.,. Clowes,R.M., and E l l i s , R . M . 1977. Depth l i m i t s on t h e M - d i s c c n t i n u i t y i n t h e s o u t h e r n Rocky M o u n t a i n T r e n c h , Canada. B u l l . S e i s m . S o c . Am., 67, i n p r e s s . S t a c e y , S . A . 1S73. G r a v i t y a n o m a l i e s , c r u s t a l s t r u c t u r e and p l a t e t e c t o n i c s i n t h e C a n a d i a n C o r d i l l e r a . C a n . J . E a r t h S c i . , 10, pp. 615-628. 8 2 U l r y c h , T . J . and B i s h o p f T . H . 1975. Maximum entropy spec t r a l ana lys i s and autoregressive decomposition. Rev. Geophys. Space Phys . , 13, pp. 183-201. Wanless S.K. and Ressor J . E . 1974. Frecamcrian z i r con age of orthcgneiss in the Shuswap Metamorphic Complex, B r i t i s h Columtia. Can. J . Earth S c i . , 12, pp. 326-332. Wheeler , J .O. and Gabr i e l s e ,H . 1972. The C o r d i l l e r a n s t r u c t u r a l province. In : Var i a t ions in Tectonic Styles i n Canada, R.A. Pr ice and R.J.W. Douglas (Eds . ) . Geol . assoc. Can . , Spec. Pap. 11, pp. 9-81. W h i t e , * . R . H . , Bone,M.S. , and Milne , W.G-. 1 968. Seismic r e f r a c t i o n surveys in B r i t i s h Columbia-A prel iminary i n t e r p r e t a t i o n . Am. Geophys. Un. Geophys. Mcnc;12, pp. 81-91. Wickens ,A. J . 1977. The upper mantle of southern B r i t i s h Columtia . Can. J . Earth S c i . , 14, i n press. Wiggins,R.A. and Helmterger,D.V. 1974. Synthetic seismogram computation by expansion i n general ized rays . Geophys. J . E . a s t r . Soc. , 37, pp. 73-90. Wiggins,R.A. 1976. Body wave amplitude c a l c u l a t i c n s - I I . Geophys. J . R. a s t r . S o c , 46, pp. 1-10. York ,E . 1969. Least sguares f i t t i n g of a s t ra ight l i n e with corre la ted e r ro r s . Earth Planet . S c i . L e t t . 5, pp. 320-324. 

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.831.1-0052994/manifest

Comment

Related Items