Afterslip and Spontaneous Aseismic Slip on the Anza Segment of the San Jacinto Fault Zone, Southern California

Abstract Understanding the interplay of seismic and aseismic slip is key in hazard evaluation. It particularly important to know if same or nearby fault segments can host different modes understand transition between slip. We investigate this trifurcation area Anza segment San Jacinto where deep creep driving seismicity below geodetic locking depth has been proposed. focus on periods following local moderate‐sized earthquakes by combining occurrence highly correlated families (i.e., closely spaced partially overlapping events) that we describe here as near‐repeating earthquakes, seismicity, borehole strainmeter data. find all M w > 4.5 2010 2020 triggered afterslip with coplanar off‐fault microseismicity. These observations include newly detected June 10, 2016 5.2 April 4, 4.9 earthquakes. Afterslip geometries defined earthquake are consistent strain change observations. conclude similar low‐frequency within tremor, be useful indicators transients reveal faulting complexities during Further, identify first evidence spontaneous region from two minor faults 2015. Taken together, our support a model microseismicity located transitional at bottom seismogenic zone spatially heterogeneous frictional properties produce frequent near Anza.