A Comprehensive Earthquake Focal Mechanism Catalog for Nevada Obtained Through Deep Learning Algorithms

Avigyan Chatterjee, Gaurav Srikar, Colin N. Pennington, Daniel T. Trugman, & William Walter

Published September 8, 2024, SCEC Contribution #13734, 2024 SCEC Annual Meeting Poster #066

The state of Nevada ranks among the most seismically active regions in the United States, characterized by numerous active fault systems throughout the Walker Lane and Basin and Range tectonic areas. Despite the high seismic activity rates, Nevada currently lacks a comprehensive catalog of earthquake focal mechanisms that could enhance our understanding of seismotectonic processes. Determining focal mechanisms for small earthquakes is challenging due to the difficulty in distinguishing phase arrivals and first-motion polarities from noise. To address this, we augment the first-motion polarity database maintained by the Nevada Seismological Laboratory with additional measurements obtained using a convolutional neural network algorithm. We further enhance polarity data with new measurements of S/P amplitude ratios to provide additional constraints on event mechanisms. By incorporating both existing and newly obtained data, we construct a comprehensive focal mechanism catalog for Nevada from 2008 to 2023, utilizing a revised implementation of the HASH method originally developed by Hardebeck and Shearer (2002), known as SKHASH (Skoumal et.al, 2024). This new focal mechanism catalog allows us to analyze changes in focal mechanism characteristics resulting from significant mainshocks, such as the 2020 Mw 6.5 Monte-Cristo earthquake, and other prominent sequences, including those at Spanish Springs, Hawthorne, Nine-Mile Ranch, and Sheldon. The enhanced resolution of this catalog will be crucial for advancing our understanding of the crustal stress field, earthquake-triggering mechanisms, fault zone geometry, and strain partitioning across the state.

Citation
Chatterjee, A., Srikar, G., Pennington, C. N., Trugman, D. T., & Walter, W. (2024, 09). A Comprehensive Earthquake Focal Mechanism Catalog for Nevada Obtained Through Deep Learning Algorithms. Poster Presentation at 2024 SCEC Annual Meeting.

Related Projects & Working Groups
Stress and Deformation Over Time (SDOT)