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Reexamining Historical Yellowstone Swarms Using a Relocated Earthquake Catalog From 1995-2023

Description: 

The Yellowstone region is the most seismically active area in the U.S. Intermountain West with an average of ~1,500 – 2,500 earthquakes per year. About half of Yellowstone seismicity occurs as part of earthquake swarms which have been attributed to processes such as hydrothermal fluid migration, magma injection or creep along faults. Swarms have been examined and relocated using a multitude of methods. We have generated a high-precision relocated earthquake catalog of over 50,000 events between 1995 and 2023 for the Yellowstone region. These relocations were done using NonLinLoc – Source Specific Station Terms with Coherence (NLL-SSST-Coherence), a nonlinear high-precision earthquake location method that builds on the conventional NLL method. The NLL source specific station terms are created iteratively using a 3D velocity model and waveform coherence is used to reduce arrival time errors. We compare swarm absolute locations from NLL-SSST-coherence with 1D routine locations produced by the University of Utah Seismograph Stations and with 3D relocations using standard NLL. Using a precise catalog allows us to examine in more detail the background seismicity and reactivations of swarms in highly active areas such as Yellowstone Lake and the Madison Plateau. Initial results show an improvement in location quality in almost all events and swarms converging on previously unobserved linear features. These findings suggest that using a more advanced location method for swarm events could reveal previously unobserved structures and dynamics of historical and modern swarms.

Session: Advanced Geophysical Observations, Analytical Methods, and New Insights for Earthquake Swarms - I

Type: Oral

Date: 4/15/2025

Presentation Time: 02:30 PM (local time)

Presenting Author: Theresa

Student Presenter: Yes

Invited Presentation: 

Poster Number: 109

Authors