Is Dynamically Triggered Seismicity Comparable to Background Seismicity?
Description:
Earthquakes can be dynamically triggered by the passing waves of events from distant faults. Identifying dynamic triggering mechanisms offers tangible hope in revealing earthquake nucleation processes. Delayed dynamic triggering is frequently observed, and such cases are likely driven by nonlinear processes that differ from typical stress triggering. This brings into question whether or not they reflect the same nucleation processes. Here we investigate the physical mechanisms of triggered seismicity in southern California using a variety of independent datasets related to faulting environments and earthquake source characteristics. Within the spatial and temporal resolution afforded by these data, we find weak correlations between triggering occurrence and surface fault trace complexity, focal mechanism diversity, and fault type. Such low correlations suggest similar faulting environments for the triggered and background seismicity. We find that the triggered seismicity may have lower stress drop and b-value estimates compared to background seismicity. The lower stress drops and b-values imply that the driving mechanisms might be different between triggered and background earthquakes. Additionally, about 85% percent of triggered sequences do not begin with the largest event. About 50% of these triggered sequences have migration velocities above 0.25 km/hr and Omori p-values below 0.75. These characteristics suggest that the triggered seismicity is akin to earthquake swarms, which are often driven by aseismic slip or fluid migration. These processes are likely reflected in the lower stress drops and b-values of the triggered seismicity. Our findings suggest that the triggered seismicity are likely by-products of additional, localized processes activated by the passing waves, such as aseismic slip or fluid movement.
Session: Special Applications in Seismology - I
Type: Oral
Date: 5/1/2024
Presentation Time: 04:30 PM (local time)
Presenting Author: Nicolas
Student Presenter: Yes
Invited Presentation:
Authors
Nicolas DeSalvio Presenting Author Corresponding Author ndesalvio@ucsd.edu University of California, San Diego |
Wenyuan Fan wenyuanfan@ucsd.edu University of California, San Diego |
Andrew Barbour abarbour@usgs.gov U.S. Geological Survey |
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Is Dynamically Triggered Seismicity Comparable to Background Seismicity?
Category
Special Applications in Seismology