SCEC2024 Poster #027: Probing Seismicity Secrets with Five Nodal Arrays around the San Jacinto Fault

Group A, Poster #027, Seismology

Probing Seismicity Secrets with Five Nodal Arrays around the San Jacinto Fault

Taiga Morioka, Florent Brenguier, Elizabeth S. Cochran, Wenyuan Fan, Quentin Higueret, Daniel D. Hollis, Peter M. Shearer, Frank L. Vernon, John E. Vidale, Ruoyan Wang, & Hao Zhang

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Poster Presentation

2024 SCEC Annual Meeting, Poster #027, SCEC Contribution #13751 VIEW PDF

The spatiotemporal relationship between the frequent small earthquakes and the much rarer occurrence of large earthquakes is not yet clear; clarifying that connection is fundamental to better understanding fault mechanics and earthquake nucleation. With more complete catalogs we can address critical questions important to earthquake hazard and forecasting, such as the prevalence and mechanics of foreshocks, the spatial-temporal evolution of swarms, and the fine-scale structure of faults. Recent advances in template-matching and machine-learning approaches have improved our ability to detect and locate events, resulting in catalogs that are more complete than those developed using routine net...work processing. However, improvements to the detection of tiny earthquakes can still be made, and a hidden frontier of microearthquakes remains to be examined. Our recent analysis showed that beamforming applied to a large-N nodal array on the San Jacinto Fault detects about five times more earthquakes than those in the QTM catalog of Ross et al. (2019), which itself has many times more events than the standard Southern California Seismic Network (SCSN) catalog.

We plan to build on these advances by deploying five 80-element nodal arrays of 100-m aperture around an active portion of the San Jacinto Fault for four months from late 2024 to early 2025. A 100-m aperture is practical for deploying seismometers, ensuring the equipment can be efficiently installed and maintained over the study period. Furthermore, our analyses of coherence and noise in existing arrays find that a 100-m grid of 80 sensors provides sufficient signal-to-noise improvement to detect very small earthquakes.

Multiple arrays will enhance our ability to detect and locate tiny earthquakes using beamforming approaches to detect both P and S arrivals. Further enhancement with template matching, waveform cross-correlation, and differential location techniques will provide improved resolution of seismicity and perhaps fault structure. We hope this multiple-array project will provide new insights into fault mechanics and seismicity by improving our ability to detect microseisms.
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