Delayed and Sustained Remote Triggering of Small Earthquakes in the San Jacinto Fault Region by the 2014 Mw 7.2 Papanoa, Mexico Earthquake

Abstract

We apply a move max matched-filter method to detect heightened seismicity triggered in the San Jacinto fault (SJF) zone, by the 2014 Mw 7.2 Papanoa, Mexico earthquake. The move max matched filter detects 5.4 and 1.7 times the number of earthquakes in the Southern California Seismic Network catalog and those detected by the matched-filter method, respectively. The seismicity rate increases significantly ~3.5 hr after the passage of the teleseismic waves and persists above the background level for about 1 week. This observation of delayed triggering may imply that dynamic stresses had initiated a time-dependent advance to failure or a secondary process. A highly active triggered patch is located ~10 km west of the SJF near Anza, on a previously unmapped fault. Focal mechanisms and a best fit plane suggest a normal fault perpendicular to the SJF. The unmapped fault may indicate higher seismic hazard in the surrounding areas if a large earthquake nucleated around the Anza seismic gap.