Systematic Search for Repeating Earthquakes along the Central San Jacinto Fault

Dongdong Yao, Zhigang Peng, Clara Daniels, & Xiaofeng Meng

Submitted August 15, 2017, SCEC Contribution #7856, 2017 SCEC Annual Meeting Poster #068

Microearthquakes are much more abundant along the San Jacinto Fault (SJF) when compared to the nearby South San Andreas Fault (SAF), although their slip rates are somewhat similar. Many studies proposed that “brittle creep” could explain the seismicity within the deep seismogenic zone, acting like a transition zone bridging the locked and free sliding regions. If such creep zone exists, we would expect to observe repeating earthquakes similar to those observed at the Parkfield section of the SAF. With implemented catalogs by using waveform matching technique, Meng and Peng [2016] revealed anomalous large aftershock zones below geodetically inferred locking depth for M>4 earthquake along the central SJF. Moreover, ~30 repeating sequences with 3 or more events each were identified 5 days before and 10 days after the 2001 M5.0 Anza earthquake. In this study, we perform a more systematic investigation for repeating earthquake sequences along the central SJF. We select ~9,8700 events around the central SJF within the box region (33.1-33.8N, 117-116W) from the relocated catalog (1981-2016) in Southern California [Hauksson et al., 2012], and run an event-based waveform cross-correlation (CC) using the AZ and PBO networks. We export event pairs as repeating pairs with CC values higher than 0.95 on at least two stations [Meng et al., 2015], followed by clustering and refined relocation. The obtained repeating clusters can be used as strain meters to infer deep creep rate along the SJZ, and quantify their occurrence patterns with nearby and large distant earthquakes. By a systematic detection of repeating earthquakes, we hope to improve our understanding of fault slip behaviors in the middle crust, partition between seismic and aseismic deformation, as well as potential depth-extent of faulting during large earthquakes. Updated results would be presented at the meeting.

Yao, D., Peng, Z., Daniels, C., & Meng, X. (2017, 08). Systematic Search for Repeating Earthquakes along the Central San Jacinto Fault. Poster Presentation at 2017 SCEC Annual Meeting.

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