History of late Holocene earthquakes at the Willow Creek site on the Nephi segment, Wasatch fault zone, Utah

Paleoseismology of Utah
By: , and 

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Abstract

This 43-page report presents new data from the Willow Creek site that provides well-defined and narrow bounds on the times of the three youngest earthquakes on the southern strand of the Nephi segment, Wasatch Fault zone, and refines the time of the youngest earthquake to about 200 years ago. This is the youngest surface rupture on the entire Wasatch fault zone, which occurred about a century or less before European settles arrived in Utah. Two trenches at the Willow Creek site exposed three scarp-derived colluvial wedges that are evidence of three paleoearthquakes. OxCal modeling of ages from Willow Creek indicate that paleoearthquake WC1 occurred at 0.2 ± 0.1 ka, WC2 occurred at 1.2 ± 0.1 ka, and WC3 occurred at 1.9 ± 0.6 ka. Stratigraphic constraints on the time of paleoearthquake WC4 are extremely poor, so OxCal modeling only yields a broadly constrained age of 4.7 ± 1.8 ka. Results from the Willow Creek site significantly refine the times of late Holocene earthquakes on the Southern strand of the Nephi segment, and this result, when combined with a reanalysis of the stratigraphic and chronologic information from previous investigations at North Creek and Red Canyon, yield a stronger basis of correlating individual earthquakes between all three sites.

Additional publication details

Publication type Report
Publication Subtype State/Local Government Series
Title History of late Holocene earthquakes at the Willow Creek site on the Nephi segment, Wasatch fault zone, Utah
Series title Paleoseismology of Utah
Volume 25
Year Published 2014
Language English
Publisher Utah Department of Natural Resources
Contributing office(s) Geologic Hazards Science Center
Description 43 p.
Online Only (Y/N) N
Additional Online Files (Y/N) N