Examining the role of elevated and sustained strain in dynamically triggering earthquakes on the Anza section of the San Jacinto fault

Bulletin of the Seismological Society of America
By: , and 

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Abstract

Microearthquakes can be dynamically triggered in southern California by remote earthquakes. However, directly connecting dynamic triggering mechanisms with observational data remains challenging. One proposed failure mechanism suggests that both the amplitude and duration of cyclic fatigue caused by the passing seismic wave contribute to triggering occurrence. Here, we measure dynamic strains recorded by borehole strainmeters in the Anza section of the San Jacinto fault zone from 710 earthquakes that occurred over 300 km away between 2008 and 2017 to systematically investigate the role of elevated and sustained strain in controlling dynamic triggering. We design a suite of tests to evaluate whether specific amplitude thresholds and durations of strain can predict dynamic triggering cases. We further test whether the peak dynamic strain (PDS) can predict triggering occurrence in combination with the strain amplitude and duration. Based on these tests, there is no strain amplitude–duration threshold that can distinguish triggering occurrence in Anza. Dynamic triggering is more likely to occur if a remote earthquake causes a PDS above 100 nanostrain, though many cases were triggered at smaller PDSs. The lack of clear correlation between triggering and characteristics of the dynamic strain field suggests that the tested features of the incoming waves do not determine triggering occurrence and local fault conditions and slip processes are more important in controlling dynamic triggering in Anza.

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Publication type Article
Publication Subtype Journal Article
Title Examining the role of elevated and sustained strain in dynamically triggering earthquakes on the Anza section of the San Jacinto fault
Series title Bulletin of the Seismological Society of America
DOI 10.1785/0120240079
Issue Online First
Publication Date February 11, 2025
Year Published 2025
Language English
Publisher Seismological Society of America
Contributing office(s) Earthquake Science Center
Description 17 p.
Country United States
State California
City Anza
Other Geospatial southern California
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