Remote Dynamic Triggering of Intermediate-Depth Earthquakes in the Mariana Subduction Zone Following the 2012 Indian Ocean Earthquakes
Description:
Although dynamic triggering can provide important insights into earthquake faulting mechanisms, there have been no previous reports of remote dynamic triggering of intermediate-depth earthquakes. The 2012 Indian Ocean Mw 8.6 and Mw 8.2 earthquakes were unusually prolific in triggering remote shallow earthquakes worldwide. Analysis of data from a temporary, amphibious array deployed over the Mariana subduction zone reveals a dynamically triggered sequence of intermediate-depth earthquakes following the Mw 8.2 aftershock. The first event occurs immediately after the long-period Rayleigh wave arrival. The intermediate-depth seismicity rate increases to 6 times the background seismicity rate in the hour immediately following and continues at twice the background seismicity rate for the subsequent 24 hours, with the triggered events occurring at depths of 160 to 240 km beneath the Northern Mariana Islands. Using synthetic seismograms and a finite difference technique, we calculate displacement and strain as a function of depth at the event locations. Unlike most shallow triggered seismicity from the 2012 events, the triggered intermediate-depth events show Rayleigh wave amplitudes larger than Love wave amplitudes, since the event azimuth lies along a Love wave node. These results suggest that intermediate depth faults are critically stressed, such that extremely small strains can cause seismicity. We suggest that the association of intermediate-depth triggering during the passage of the Rayleigh wave indicates that slight changes in density associated with the wave passage may trigger dehydration reactions that are proposed as a mechanism of intermediate-depth events.
Session: New Observations and Modeling of Triggered Seismicity [Poster]
Type: Poster
Date: 4/19/2023
Presentation Time: 08:00 AM (local time)
Presenting Author: Amanda Price
Student Presenter: No
Invited Presentation:
Authors
Amanda Price Presenting Author Corresponding Author price54@llnl.gov Lawrence Livermore National Laboratory |
Douglas Wiens doug@wustl.edu Washington University in St Louis |
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Remote Dynamic Triggering of Intermediate-Depth Earthquakes in the Mariana Subduction Zone Following the 2012 Indian Ocean Earthquakes
Category
New Observations and Modeling of Triggered Seismicity