We use relocated catalogs of microearthquakes to investigate earthquake interaction along sections of the Sargent, Calaveras, and San Andreas faults in California. We examine the stress dependence of seismicity rate change along the three fault segments and find that the seismicity rate following a mainshock decays approximately as 1/time, the duration of the aftershock activity seems to be independent of distance from the mainshock, and the seismicity rate at lag times of up to about 100 sec is nearly constant. In the San Andreas and the Calaveras catalogs, where the return of the seismicity rate to the background level is well resolved, we find that the return to the background in the distance range of 1–2 rupture radii from a previous earthquake is preceded by a period during which the seismicity rate falls about 30% below the background rate. We also examine the effect of a stress step on earthquake size distribution along these faults and find that the exponent of the power-law distribution of earthquake magnitudes within 104 sec of a previous earthquake is significantly lower than that of the long term. While the 1/time decay of seismicity rate, the independence of aftershock duration from distance from the mainshock, and the constant seismicity rate at short lag times are predicted by Dieterich's (
For comparison with our observations, we simulate earthquake activity on an inherently discrete fault model that is governed by an approximate constitutive friction law similar to the one used by Dieterich (
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