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Ubiquitous Earthquake Dynamic Triggering in Southern California

Description: 

Earthquakes can be dynamically triggered by the passing waves of events from distant faults. Observations of frequent dynamic triggering offers tangible hope in revealing earthquake nucleation processes. However, the physical mechanisms behind earthquake dynamic triggering remain 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 assumptions about the 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 up to 70% 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 triggering rate means that earthquakes are triggered about every 4 days in the region, albeit at different locations. 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 faulting conditions. Further, the occurrence of dynamic triggering does not seem to correlate with ground motion (e.g. peak ground velocity) at the triggered sites. These observations indicate that nonlinear processes may have primarily regulated the dynamic triggering cases. We investigate one such process, material fatigue, using the duration of elevated strain recorded by strainmeters in southern California. In contrast to peak ground motion values, strain energy dissipation is a relatively strong diagnostic of triggering conditions.

Session: Deciphering Earthquake Clustering for the Better Understanding of Crustal Deformation Mechanisms

Type: Oral

Date: 4/20/2023

Presentation Time: 02:30 PM (local time)

Presenting Author: Nicolas D. DeSalvio

Student Presenter: Yes

Invited Presentation: Yes

Authors