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Analysis of Yellowstone Earthquake Swarms After Relocating Using Nonlinloc-Ssst and a 3D Velocity Model

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. High-precision earthquake locations can be used to understand the structures where swarms occur and the underlying causes of the swarm seismicity. NonLinLoc (NLL) is a nonlinear high-precision earthquake location method that has been shown to produce higher-quality absolute locations than conventional methods. We have applied a more advanced version of NLL, NonLinLoc – Source Specific Station Terms with Coherence (NLL-SSST-coherence) to ~40 years of Yellowstone seismic data recorded from 1984 to 2024 to obtain high-precision absolute earthquake locations. 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 will compare the 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. Initial results indicate that the NLL-SSST-coherence locations show an improvement over both the 1D routine and standard NLL locations, and some earthquake locations converge to linear features which could indicate fault structures. These findings suggest that using a more advanced location method for swarm events could be an important step in understanding the structures and dynamics of earthquake swarms. It also suggests that including the use of NLL-SSST-coherence in routine location analysis could improve the “realtime” interpretation of Yellowstone swarm activity.

Session: Advances in Operational and Research Analysis of Earthquake Swarms [Poster Session]

Type: Poster

Room: Exhibit Hall

Date: 5/3/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Theresa Czech

Student Presenter: Yes

Additional Authors