Time-Varying Background Rates of Swarms and Aftershock Sequences in the San Jacinto Fault Zone in Southern California

Valeria Villa, & Zachary E. Ross

Published September 10, 2023, SCEC Contribution #13109, 2023 SCEC Annual Meeting Poster #025

The region along and off the San Jacinto Fault Zone is a prolific area of seismic activity. Between 2012 and 2022, there were around five magnitude 4 earthquakes and numerous earthquake swarms. Several swarms are assumed to have an aseismic driving process that may relate to crustal fluid migration. Here we study the time-varying seismicity background rates of independently triggered events from a 2012-2022 catalog built from deep learning algorithms. We apply the newly developed method called deep Gaussian process – ETAS to probabilistically model the time-variable background rate of aftershock sequences and swarms within the area. The aftershock sequences show a nearly constant background rate while the swarms exhibit a rich time-varying seismicity background rate. In these latter cases, the swarms’ background rate evolution also demonstrates some aftershock triggering. The need for a time-varying background to explain the swarm sequences continues to suggest an important role of aseismic forcing in this area. This also allows us to better quantify the aseismic factor, shedding unprecedented light on these intricate yet not-well-understood sequences.

Key Words
Swarms, Background rates, San Jacinto Fault Zone, Aftershock Sequences

Citation
Villa, V., & Ross, Z. E. (2023, 09). Time-Varying Background Rates of Swarms and Aftershock Sequences in the San Jacinto Fault Zone in Southern California. Poster Presentation at 2023 SCEC Annual Meeting.

Related Projects & Working Groups
Seismology