Skip to Main Content
Skip Nav Destination
GEOREF RECORD

Geologic setting, ground effects, and proposed structural model for the 18 March 2020 M (sub w) 5.7 Magna, Utah, earthquake

Emily J. Kleber, Adam P. McKean, Adam I. Hiscock, Michael D. Hylland, Christian L. Hardwick, Greg N. McDonald, Zachary W. Anderson, Steve D. Bowman, Grant C. Willis and Ben A. Erickson
Geologic setting, ground effects, and proposed structural model for the 18 March 2020 M (sub w) 5.7 Magna, Utah, earthquake
Seismological Research Letters (December 2020) Pre-Issue Publication

Abstract

The 18 March 2020 M (sub w) 5.7 Magna, Utah, earthquake was the largest earthquake in Utah since the 1992 M (sub L) 5.8 St. George earthquake. The geologic setting of the Magna earthquake is well documented by recent geologic mapping at 1:24,000 scale and 1:62,500 scale at and near the epicenter northeast of Magna, Utah. Subsurface fault modeling from surficial geologic mapping, structural cross sections, deep borehole data, and geophysical data reveals a complex system of faulting concentrated in the hanging wall of the Weber and Salt Lake City segments of the Wasatch fault zone including the Harkers fault, the West Valley fault zone, and the newly interpreted Saltair graben. Based on geologic and geophysical data (seismic and gravity), we interpret the mainshock of the Magna earthquake as having occurred on a relatively gently dipping part of the Salt Lake City segment, with aftershocks concentrated in the Saltair graben and West Valley fault zone. Postearthquake rapid reconnaissance of geological effects of the Magna earthquake documented liquefaction near the earthquake epicenter, along the Jordan River, and along the Great Salt Lake shoreline. Subaerial and subaqueous sand boils were identified in regions with roadway infrastructure and artificial fill, whereas collapse features were noted along the shores of the Great Salt Lake. Potential syneresis cracking and pooling in large areas indicated fluctuating groundwater likely related to earthquake ground shaking. The moderate magnitude of the Magna earthquake and minimal geological effects highlight the critical importance of earthquake research from multidisciplinary fields in the geosciences and preparedness on the Wasatch Front.


ISSN: 0895-0695
EISSN: 1938-2057
Serial Title: Seismological Research Letters
Serial Volume: Pre-Issue Publication
Title: Geologic setting, ground effects, and proposed structural model for the 18 March 2020 M (sub w) 5.7 Magna, Utah, earthquake
Affiliation: Utah Geological Survey, Salt Lake City, UT, United States
Published: 20201230
Text Language: English
Publisher: Seismological Society of America, El Cerrito, CA, United States
References: 64
Accession Number: 2021-010164
Categories: Seismology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sketch maps
N40°40'00" - N40°55'00", W112°15'00" - W111°49'60"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2021, American Geosciences Institute.
Update Code: 202103
Close Modal

or Create an Account

Close Modal
Close Modal