Study of triggered non-volcanic tremor and local earthquakes near the Anza segment of the San Jacinto fault, southern California

Non-volcanic tremor (NVT) occurring in the deep extension of the fault has been widely observed in subduction zones, but has not been observed extensively along strike-slip faults. We aim to understand whether there are different stress levels required for triggering between crustal NVT and earthquakes. We will examine the spatial and temporal occurrences of triggered tremor and earthquakes along the Anza segment of the San Jacinto Fault. The Anza section of the San Jacinto Fault (SJF) is an ideal region for more detailed observation of tremor since there is a densely spaced seismic network, including borehole stations. We used continuous waveform data, collected by 16 broadband stations of Southern California Seismic Network (SCSN) along with borehole stations from Plate Boundary Observatory (PBO) to search for NVT triggered by teleseismic surface waves. We examine teleseismic surface arrivals of large earthquakes (Mw >= 7.5 and distances > 2000 km) that occurred between 2001 and 2009 to identify triggered tremor and earthquakes. Preliminary observations suggest that only the Mw 7.8, 2002 Denali earthquake triggered detectable NVT, but more than half show local earthquakes occurring within the teleseismic surface wave arrivals. We determine, by comparing to background seismicity rates, if the local earthquakes are likely triggered by the teleseismic arrivals. In addition, we locate the NVTs observed near Anza, California using precise phase arrivals determined by waveform template matching. We use moving windows to cross-correlate tremor waveforms recorded at different stations, in order to identify identical LFEs within the tremor series. We identify template pairs with correlation coefficient with a correlation threshold over 4 times the mean absolute deviation (MAD) and matching pairs are grouped into template families of NVTs. These templates help us better define the arrival times of tremor bursts within the triggered NVT episode. We will locate the triggered NVT hypocenters using the cross-correlated arrivals and the SCEC Community Velocity Model. These NVT families can then be used to explore the spatial and temporal pattern of triggered non-volcanic tremor near the Anza segment of the San Jacinto fault.