Crustal Seismicity Across the Wyoming Craton: Earthquakes Extending to the Moho Along Laramide Structures
Year: 2025
Type: preprint
Abstract: In stable continental interiors, such as the Wyoming Craton, seismic activity remains poorly understood due to low strain rates and sparse seismic network coverage. However, significant seismic activity has been reported in recent decades, and the lack of data in this region limits the prediction of seismic hazards. To enhance our understanding of intraplate tectonic processes, we investigated seismicity across the Wyoming Craton. We utilized a machine learning-based earthquake catalog derived from USArray Transportable Array data between 2007 and 2010 and identified 2,461 earthquakes and 16,646 non-tectonic events including mining blasts. This significantly enhances the completeness of the regional catalog, capturing events down to a local magnitude of approximately 1.5. Our analysis reveals that seismic activity is predominantly distributed along basin boundaries and ridges formed during the Laramide Orogeny within broad fault zones spanning tens of kilometers. Notably, seismicity extends into the lower crust, reaching depths of 45--50 km in certain areas, suggesting that faults formed during the Laramide Orogeny penetrate the entire crust down to the Moho discontinuity. This finding challenges models of lower crustal detachment and supports the concept of whole-crustal deformation during the Laramide Orogeny. Clustering analysis reveals that most earthquakes are background events with minimal clustering, reflecting the low strain rates of the intraplate setting. Comparisons with a 50-year catalog indicate consistent seismicity rates over time, allowing probabilistic estimates of future moderate-magnitude earthquakes. We emphasize the need for continued seismic monitoring with enhanced coverage in Wyoming to better understand intraplate tectonics and improve seismic hazard assessments.
Authors: Jeong-Ung Woo, Ting Chen
Institution: Los Alamos National Laboratory
Language: English
Subfield: Geophysics
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: gold
OpenAlex ID: W4413826447