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Holocene behavior of the Brigham City segment; implications for forecasting the next large-magnitude earthquake on the Wasatch fault zone, Utah

Stephen F. Personius, Christopher B. DuRoss and Anthony J. Crone
Holocene behavior of the Brigham City segment; implications for forecasting the next large-magnitude earthquake on the Wasatch fault zone, Utah
Bulletin of the Seismological Society of America (December 2012) 102 (6): 2265-2281

Abstract

The Brigham City segment (BCS), the northernmost Holocene-active segment of the Wasatch fault zone (WFZ), is considered a likely location for the next big earthquake in northern Utah. We refine the timing of the last four surface-rupturing ( approximately M (sub w) 7) earthquakes at several sites near Brigham City (BE1, 2430+ or -250; BE2, 3490+ or -180; BE3, 4510+ or -530; and BE4, Formula B.P.) and calculate mean recurrence intervals (1060-1500 yr) that are greatly exceeded by the elapsed time ( approximately 2500 yr) since the most recent surface-rupturing earthquake (MRE). An additional rupture observed at the Pearsons Canyon site (PC1, Formula B.P.) near the southern segment boundary is probably spillover rupture from a large earthquake on the adjacent Weber segment. Our seismic moment calculations show that the PC1 rupture reduced accumulated moment on the BCS about 22%, a value that may have been enough to postpone the next large earthquake. However, our calculations suggest that the segment currently has accumulated more than twice the moment accumulated in the three previous earthquake cycles, so we suspect that additional interactions with the adjacent Weber segment contributed to the long elapse time since the MRE on the BCS. Our moment calculations indicate that the next earthquake is not only overdue, but could be larger than the previous four earthquakes. Displacement data show higher rates of latest Quaternary slip ( approximately 1.3 mm/yr) along the southern two-thirds of the segment. The northern third likely has experienced fewer or smaller ruptures, which suggests to us that most earthquakes initiate at the southern segment boundary. Online Material: Cross sections, age estimates, evaluation of Box Elder delta earthquake chronology, code for OxCal models, trench logs, sources of surface offset data, and description of Call Fort gravel pit fault exposures.


ISSN: 0037-1106
EISSN: 1943-3573
Coden: BSSAAP
Serial Title: Bulletin of the Seismological Society of America
Serial Volume: 102
Serial Issue: 6
Title: Holocene behavior of the Brigham City segment; implications for forecasting the next large-magnitude earthquake on the Wasatch fault zone, Utah
Affiliation: U. S. Geological Survey, Denver, CO, United States
Pages: 2265-2281
Published: 201212
Text Language: English
Publisher: Seismological Society of America, Berkeley, CA, United States
References: 84
Accession Number: 2013-010696
Categories: Seismology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Supplemental information/data is available in the online version of this article
Illustration Description: illus. incl. 2 tables, geol. sketch maps
N41°00'00" - N42°00'00", W114°04'60" - W111°52'60"
Secondary Affiliation: Utah Geological Survey, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Seismological Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201308
Program Name: USGSOPNon-USGS publications with USGS authors
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