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Figure 1: S-wave velocity anomaly from Zhang and Tanimoto (1992) taken perpendicular to the Mid-Atlantic ridge axis near the hotspot St. Helena which lies to the east of the ridge. The hot spot lies above the deep part of the low velocity anomaly. The elongation of the anomaly towards the ridge suggests that it represents a channel for mantle flow from the hotspot to the ridge axis.

 
Figure 2: Spatial relationship between reflectors imaged by the INDEPTH (International Deep Profiling of Tibet and the Himalaya) group on the northern side of the Himalaya (Box) and well-located thrust earthquakes. The upper reflector named the Main Himalayan Thrust (MHT) is thought to represent the decollement between the Tibetan and under-thrusting Indian crust.

 
Figure 3: Peak acceleration observed during the Loma Prieta earthquake compared to acceleration predicted from weak motion studies showing that at distances less than 50 km the weak motion overestimates the strong motion. (From Chin and Aki, 1991). A frequency dependent Q or quality factor Q(f) (upper right hand side of the figure) was used by Chin and Aki to calculate predicted ground motion, where f is frequency.