Displaying the Structure and Rheological Properties of a Fault Zone in the Characteristics of Background Seismicity

Spatial heterogeneity of structural and rheological properties of a fault is one of the key factors that determine the dynamics of its deformation. This work analyzes spatiotemporal patterns of seismicity localization in several segments of the San Andreas fault zone. Groups of background and clustered events are distinguished in the flow of seismic events. It is shown that background events exhibit structural features of the fault. Asperities on the fault plane appear as dense clusters of background events. Foci of strong earthquakes with magnitudes exceeding the maximum magnitude of background events by 1.5‒2 units completely rupture at least one asperity. The fault area located between the asperities controls the slow postseismic slip and, consequently, postseismic aftershock activity. The number of aftershocks is maximum at the boundary of the earthquake focal area and decreases monotonically with distance from the hypocenter. In the area between the asperities, the velocity of aftershock migration is 0.01–10 km/day.