EARTHQUAKE FREQUENCY DISTRIBUTION AND THE MECHANICS OF FAULTING S. G. Wesnousky and C. H. Scholz Lamont-Doherty Geological Observatory of Columbia University

The level of intraplate seismicity in Japan generally shows a positive correlation with the density of Quaternary faulting. In southwest Japan, wherintraplate seismicity is concentrated on land, rates of seismic moment re- predicted from the geologic record is virtually identical to that seen with the 400-year record of seismicity. In contrast, if it is assumed that earthquakes on each fault occur according to the Gutenberg-Richter relation, we obtain poor agreement with the observed seismicity. Thus, while regional seismicity satisfies the relation log NA - B s log M 0 (or equivalently, log N = a - b s log M, where M is magnitude), it appears that seismicity on individual faults does not. This further implies that the primary factor that leads to the magnitude frequency distribution in regional seismicity studies is the relative distribution of the slip rates and lengths of preexisting faults.