Group A, Poster #053, Seismology

What Causes Ubiquitous Earthquake Dynamic Triggering in Southern California?

Nicolas DeSalvio, Wenyuan Fan, & Andrew J. Barbour
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Poster Presentation

2023 SCEC Annual Meeting, Poster #053, SCEC Contribution #13119 VIEW PDF
Although there are now global observations spanning multiple decades of earthquakes triggered by teleseismic waves, the physical mechanisms behind this phenomenon remain unclear. In this study, we systematically identify cases of dynamic triggering in Southern California from 2008-2017 and investigate the associated local ground motion at the locations of triggered events with a variety of waveform metrics. We use the Quake Template Matching catalog and new statistical methods that do not assume the background seismicity probability density function for the analysis and reduce false positive detections (see DeSalvio and Fan, 2023; doi:10.1029/2023JB026487). Our methods have the flexibility t...o account for spatiotemporally evolving fault conditions. We observe that dynamically triggered seismicity is frequent and widespread in Southern California. We find that adjacent fault segments are rarely triggered by the same earthquakes, suggesting that the process is primarily governed by local conditions. There are no obvious correlations between the dynamic triggering occurrence and common wavefield metrics including peak ground velocity, peak frequency, kinetic energy, or the frequency content of the ground motion at the triggering sites. These observations indicate that time-dependent, nonlinear processes may have a primary role in regulating dynamic triggering. To explore this further, we use Network of the Americas strain data in Southern California to estimate strain duration at various critical strain values and investigate possible relations with dynamic triggering patterns. The strain duration relates to cyclic loading from the seismic waves and energy dissipation: elevated and sustained levels of strain duration may facilitate crack development and growth, eventually triggering earthquakes. Our findings may help guide new experiment and simulation designs to uncover the physical mechanisms causing earthquake dynamic triggering.