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Seismic analysis of the 2020 Magna, Utah, earthquake sequence: Evidence for a listric Wasatch fault

Guanning Pang·Keith D. Koper·Maria Messimeri·Kristine L. Pankow·Ben Baker·Jamie Farrell·James Holt·J. Mark Hale·Paul B. Robertson·Relu Burlacu·James C. Pechmann·Katherine Whidden·Monique M. Holt·Amir Allam·Christopher B. DuRoss
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Abstract

The 18 March 2020 M w 5.7 Magna earthquake near Salt Lake City, Utah, offers a rare glimpse into the subsurface geometry of the Wasatch fault system—one of the world's longest active normal faults and a major source of seismic hazard in northern Utah. We analyze the Magna earthquake sequence and resolve oblique-normal slip on a shallow (30–35°) west-dipping fault at ~9- to 12-km depth. Combined with near-surface geological observations of steep dip (~70°), our results support a curved, or listric, fault shape. High-precision aftershock locations show the activation of multiple, low-angle (<30–35°) structures, indicating the existence of a complicated fault system. Our observations constrain the deep structure of the Wasatch fault system and suggest that ground shaking in the Salt Lake City region in future Wasatch fault earthquakes may be higher than previously estimated.

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Geophysical Research LettersArticle
90° N90° S · 180° W ← longitude → 180° E
Source-reported bounding extent: 40.64730356252251° to 40.851215574282456° latitude; -112.20336914062497° to -111.79687499999997° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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Guanning Pang, Keith D. Koper, Maria Messimeri, Kristine L. Pankow, Ben Baker, Jamie Farrell, James Holt, J. Mark Hale, Paul B. Robertson, Relu Burlacu, James C. Pechmann, Katherine Whidden, Monique M. Holt, Amir Allam, Christopher B. DuRoss. 2020-09-10. Seismic analysis of the 2020 Magna, Utah, earthquake sequence: Evidence for a listric Wasatch fault. https://doi.org/10.1029/2020gl089798

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