Geoscience Reference
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(a)
A
N
(b)
N
C
1
B
A
W
2
C
B
100 km
S
(c)
N
W
S
Figure 4.55.
(a) Locations of earthquakes 1 and 2 on the Mid-Atlantic Ridge.
(b) Directions of first motion for earthquake 1. (c) Directions of first motion for
earthquake 2. Symbols denote compression and dilatation as in Fig. 4.54.
13. Contrast the distribution of earthquake foci in and around the Atlantic and Pacific
Oceans and describe the mechanism of earthquakes on the mid-ocean ridges. What
light do these facts throw on the plate motions? (Cambridge University Natural Sci-
ences Tripos IB, 1976.)
14. The outline map in Fig. 4.55(a) shows the positions of two earthquakes recorded on
the Mid-Atlantic ridge. Focal spheres of earthquakes 1 and 2 are also shown (Figs.
4.55(b) and (c)).
