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

September 10, 2020

The 18 March 2020 Mw 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.

Publication Year 2020
Title Seismic analysis of the 2020 Magna, Utah, earthquake sequence: Evidence for a listric Wasatch fault
DOI 10.1029/2020GL089798
Authors 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 DuRoss
Publication Type Article
Publication Subtype Journal Article
Series Title Geophysical Research Letters
Index ID 70224750
Record Source USGS Publications Warehouse
USGS Organization Geologic Hazards Science Center