Abstract
AbstractWe 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.
Highlights
With the implementation of globally distributed seismic networks and improved earthquake detection/location methods, large earthquakes have been widely observed to change the seismicity rate both dynamically and in a delayed manner, within regions hundreds to thousands of kilometers away (Ghosh et al, 2009; Hill et al, 1993; Mendoza et al, 2016; Meng & Peng, 2014; Shelly et al, 2011)
Local earthquakes in the San Jacinto fault region triggered by the Mw 7.2 Papanoa earthquake are shown in Figures 2b and 2c
We use the move max matched‐filter (MMMF) method to capture delayed triggering of small local earthquakes in the San Jacinto Fault Zone (SJFZ) near the Anza Gap in California
Summary
With the implementation of globally distributed seismic networks and improved earthquake detection/location methods, large earthquakes have been widely observed to change the seismicity rate both dynamically (instantaneously) and in a delayed manner, within regions hundreds to thousands of kilometers away (Ghosh et al, 2009; Hill et al, 1993; Mendoza et al, 2016; Meng & Peng, 2014; Shelly et al, 2011). The dynamic stress changes due to large earthquakes at teleseismic distances have been estimated to be between 0.1 and 1 MPa (Prejean & Hill, 2009); the occurrence of triggered earthquakes indicates that faults in that region are sensitive to small stress perturbations. For this reason, studies of triggered earthquakes provide clues to understanding the state of stress of critically stressed and potentially seismically hazardous faults (Johnson et al, 2015). Understanding the stress state and the conditions required for rupture nucleation in the Anza gap or on neighboring faults is important for estimating the earthquake hazard in this area
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