Paleoseismology of Utah, Volume 18: Paleoseismic investigation of the northern Weber segment of the Wasatch fault zone at Rice Creek trench site, North Ogden, Utah (SS-130)

By: C. B. DuRoss, S. F. Personius, A. J. Crone, G. N. McDonald, and D. J. Lidke

This Utah Geological Survey Special Study, Paleoseismic Investigation of the Northern Weber Segment of the Wasatch Fault Zone at the Rice Creek Trench Site, North Ogden, Utah, is the eighteenth report in the Paleoseismology of Utah series. This series makes the results of paleoseismic investigations in Utah available to geoscientists, engineers, planners, public officials, and the general public. These studies provide critical information regarding paleoearthquake parameters such as earthquake timing, recurrence, displacement, slip rate, fault geometry, and segmentation, which can be used to characterize potential seismic sources and evaluate the long-term seismic hazard of Utah’s Quaternary faults.

This report presents new paleoseismic information for the northern Weber segment of the Wasatch fault zone, collected as part of a joint Utah Geological Survey and U.S. Geological Survey seismic-hazard evaluation. The purpose of the study was to address uncertainties in the number, timing, and displacement of surface-faulting earthquakes on the segment. To address these issues, two trenches were excavated at Rice Creek in North Ogden. The trenches exposed evidence for three surface-faulting earthquakes in an upper fault zone, four earthquakes in a lower fault zone, and two earthquakes in an antithetic fault zone. Using stratigraphic and structural relations, and radiocarbon and luminescence ages, the earthquakes within the three fault zones were resolved into a preferred scenario of six Holocene earthquakes at the site. The study also substantiated an approximately 500-year-old earthquake identified in a previous investigation on the northern Weber segment that may represent a partial-segment rupture.

Other Information:
Published: 2009
Pages: 27 p. + 9 p. appendices
Plates: 2 pl.
Location: Davis County and Weber County