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(b)
W
E
Vancouver Island
Mainland
0
5.3-6.4
1.8-3.25
6.0-6.82
4.0-5.9
6.4-6.75
6.85-7.28
10
6.35
6.95
8.1-8.33
7.15
20
6.4-6.95
7.1-7.18
30
7.4-7.85
(M)
40
7.7
7.9-8.12
50
60
0
100
200
300
Distance (km)
Figure 9.62. The Cascadia subduction zone. (a) A migrated seismic-reflection
section across Vancouver Island, Canada. Reflections C and D are associated with
the base of a major accreted terrane; reflections E may be associated with water in
the crust; reflection F is from the top of the subducting Juan de Fuca plate. (Courtesy
of R. M. Clowes.) (b) The P-wave velocity model determined from refraction and
reflection data. M, Moho. (From Drew and Clowes (1989).) (c) Perturbation in S-wave
velocity on a
250-km-long section across the subduction zone. This section is
500 km south of (a) and (b). Solid triangle, volcanic arc. Colour version Plate 26.
(After Bostock et al .(2002) and Rondenay et al .(2001).) Details from reflection lines
across the subduction zone. (d) The thin reflection zone where the subduction thrust
is locked. (e) Further to the east, where aseismic slip is occurring, the thrust shows
up as a thick band of reflections (see Fig. 9.54) (From Nedimovic et al .(2003).)
 
 
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