Paleoseismology of Utah Volume 10: Post-Bonneville paleoearthquake chronology of the Salt Lake City segment, Wasatch fault zone, from the 1999 megatrench site (MP 02-7)

By: J. P. McCalpin

This Utah Geological Survey Miscellaneous Publication, Post-Bonneville Paleoearthquake Chronology of theSalt Lake City Segment, Wasatch Fault Zone, from the 1999 Megatrench Site, is the tenth 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 on paleoearthquake parameters such as timing, recurrence, displacement, slip rate, and fault geometry, which can be used to characterize potential seismic sources and evaluate the long-term seismic hazard presented by Utah’s Quaternary faults.

This report presents the results of a paleoseismic investigation designed to date a long series of consecutive earthquakes on the Wasatch fault zone and to measure the variability of recurrence times between the events. Geologists have long recognized that the comparatively short average recurrence interval (compared to most other basin-and-range normal faults) between large surface-faulting earthquakes on the Salt Lake City segment of the Wasatch fault zone during mid- to late-Holocene time is potentially anomalous, and possibly affected by the rise and fall of Lake Bonneville. This study extends the paleoearthquake record back to Bonneville time, nearly doubling the previous record, and provides new information on the timing and periodicity of surface faulting on the Salt Lake City segment from the latest Pleistocene through the Holocene. The trench and accompanying auger hole for this study exposed 26 meters of vertical section, roughly four times that of a typical paleoseismic trench on the Wasatch fault zone, hence the name “Megatrench.”

Other Information:
Published: 2002
Pages: 37 p.
Location: Salt Lake County
Media Type: Paper Map