A spherical, self-gravitating viscoelastic earth model is used to calculate the spatial and temporal evolution of the glacially induced lithospheric stress and fault stability in North America. The predicted onset time of a pulse of earthquake activities, the mode of failure and the magnitude of instability are investigated for three sites with different distance from the former ice margin. It is found that glacial unloading is able to trigger paleo-earthquakes within the ice margin near Charlevoix (47.5 ¿N, 70.1 ¿W) and in Wabash Valley (38.5 ¿N, 87 ¿W) outside the ice margin. However, rebound stress decays away from the former ice margin, thus glacial unloading is unlikely to have triggered the large M8 earthquakes in New Madrid (36.6 ¿N, 89.5 ¿W). ¿ 2000 American Geophysical Union