A comparison of eastern North American seismic strain‐rates to glacial rebound strain‐rates

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.