An evaluation of the seismic-window theory for earthquake prediction

Abstract

The hypothesis that tides may trigger seismic events is not new. The conclusions from previous studies are mixed, but some negative results might be attributed to failure in accounting for the variation in tidal phase and fault orientation over the surface of the earth. The connection between tides and seismicity appears most convincing for studies in which the investigators either correlated the earthquakes with the magnitude and direction of tidal stress on the actual fault planes (Heaton, 1975) or restricted the data set to events in a small region over which the earthquake mechanisms would be reasonably similar (Klein, 1976; Young and Zurn, 1979). In general, these studies have dealt with only the semidiurnal fluctuations in the tidal amplitude. The intent of this study was to determine whether earthquakes in the San Francisco Bay area respond to a fortnightly fluctuation in tidal amplitude. A correlation between seismic events and any tidal period would contribute to the understanding of the earthquake process and the stress regime within which faulting occurs. But perhaps more importantly, correlations between the longer tidal periods and seismicity might provide a useful tool for earthquake prediction.