Glacial rebound strain‐rates computed using a simple Laurentide glacial loading model are of the order of 10−9 per year within the region of glaciation and extending several hundred kilometers beyond. The horizontal strain‐rates receive approximately equal contributions from horizontal and vertical velocities, a consequence of the spherical geometry adopted for the Earth model. In the eastern United States and southeastern Canada the computed strain‐rates are 1–3 orders of magnitude greater than an estimate of the average seismic strain‐rate [Anderson, 1986] and ∼1 order of magnitude greater than predicted erosional strain‐rates. The predicted glacial rebound strain‐rates are not, in general, oriented in such a way as to augment the observed state of deviatoric stress, possibly explaining why the seismic strain‐rates are much smaller than the glacial rebound strain‐rates. An exception to this may be seismically active regions in the St. Lawrence valley.

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The Whittier Narrows earthquake sequence (local magnitude, M(L) = 5.9), which caused over $358-million damage, indicates that assessments of earthquake hazards in the Los Angeles metropolitan area may be underestimated. The sequence ruptured a previously unidentified thrust fault that may be part of a large system of thrust faults that extends across the entire east-west length of the northern margin of the Los Angeles basin. Peak horizontal accelerations from the main shock, which were measured at ground level and in structures, were as high as 0.6g (where g is the acceleration of gravity at sea level) within 50 kilometers of the epicenter. The distribution of the modified Mercalli intensity VII reflects a broad north-south elongated zone of damage that is approximately centered on the main shock epicenter.

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