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Deep Quakes Beneath the Moho: Insights From the Wind River Basin, Wyoming

Description: 

Earthquakes occurring below the brittle-ductile transition zone are rare, raising questions about how rupture can extend into depths traditionally regarded as ductile. The M_W 4.8 mainshock and M_W 3.0 aftershock on September 21, 2013, near the Wind River Basin in central Wyoming, nucleated beneath the Moho and underscored key uncertainties regarding the rheological properties of the lithospheric mantle. An additional M_L 1.5 event in 2010 from the same area further confirms that these mantle earthquakes were not isolated anomalies. In this study, we analyzed USArray data (2007–2010) using a deep-learning phase picker and back-projection associator, detecting roughly 19,000 events that included quarry explosions and high seismicity in the Yellowstone region. After meticulous seismogram review, we identified at least six additional mantle earthquakes near the Wind River Basin. Their hypocenters are spatially distinct from the nearby crustal seismicity, and temperatures at those depths may have reached up to 950°C. We also note that some mantle earthquakes occurred in closely spaced pairs, suggesting self-sustained failure and structural or stress heterogeneity. We propose that thermal runaway is a more plausible mechanism for these deep earthquakes than dehydration or transformational faulting, although long-term observations will be required for further verification.

Session: Earthquakes, Lithospheric Structure, and Dynamics in Stable Continental Region - II

Type: Oral

Date: 4/17/2025

Presentation Time: 10:30 AM (local time)

Presenting Author: Jeong-Ung

Student Presenter: No

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