Possible planetary excitation of earthquakes

Several recent studies show the possibility of an important connection between the Earth's rotational motion and the number of earthquakes (Stavinschi and Souchay 2001, Shanker et al. 2001). We discuss the long-term periodic variations (30 years and 60 years) in these two geophysical processes, as well in solar activity and the Sun's celestial orbit. The similarities in such periodicities suggest that solar system dynamics may contribute to both solar and geophysical phenomena