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Ubiquitous Earthquake Dynamic Triggering in Southern California

Nicolas DeSalvio, & Wenyuan Fan

Submitted September 11, 2022, SCEC Contribution #12254, 2022 SCEC Annual Meeting Poster #038

Earthquakes can be dynamically triggered by the passing waves of events from disconnected faults. The frequent occurrence of dynamic triggering offers tangible hope in revealing earthquake nucleation processes. However, the physical mechanisms behind earthquake dynamic triggering have remained unclear, and contributions of competing hypotheses are challenging to isolate with individual case studies. Therefore, developing a systematic understanding of the spatiotemporal patterns of dynamic triggering can provide fundamental insights into the physical mechanisms, which may aid mitigation of earthquake hazards. Here we investigate earthquake dynamic triggering in Southern California from 2008 to 2017 using the Quake Template Matching catalog and an approach free from assuming an earthquake occurrence distribution. We develop a new set of statistics to examine the significance of seismicity rate changes as well as moment release changes. We show that 82% of global M≥6 events may have triggered earthquakes in Southern California and that the triggered seismicity often occurred several hours after the passing seismic waves. This high triggering rate means that earthquakes are triggered about every 3 days in the region, albeit at different locations. ​​For example, the Salton Sea Geothermal Field, San Jacinto Fault, and Coso Geothermal Field are particularly prone to triggering. Although adjacent fault segments can be triggered by the same earthquakes, the majority of triggered earthquakes seem to be uncorrelated, suggesting that the process is primarily governed by local conditions. Further, the occurrence of dynamic triggering does not seem to correlate with the peak ground velocity, peak frequency, kinetic energy, or frequency content of the ground motion at the triggering sites. These observations indicate that nonlinear processes may have primarily regulated the dynamic triggering cases. Ultimately, we aim to use a group of metrics to establish a consistent framework for distinguishing different triggering mechanisms.

Key Words
Earthquake Dynamic Triggering

DeSalvio, N., & Fan, W. (2022, 09). Ubiquitous Earthquake Dynamic Triggering in Southern California. Poster Presentation at 2022 SCEC Annual Meeting.

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