SEISMIC ACTIVITY ON NEIGHBORING FAULTS AS A LONG-TERM PRECURSOR TO LARGE EARTHQUAKES IN THE SAN-FRANCISCO BAY AREA

Activity in moderate-size earthquakes accelerated in the several decades before the large California earthquakes of 1989, 1906 and 1868. This type of precursor seems to require the presence of several major faults in close enough proximity to one another that moderate-size shocks are selectively triggered on surrounding faults during the latter stages of the cycle of strain buildup to large earthquakes. It may be possible to use quantitative aspects of similar seismic precursors to make predictions of large earthquakes on timescales of a few years to one decade. © 1990 Nature Publishing Group.