September 1, 2005

The Utah Geological Survey (UGS) recently released Bulletin 134, Consensus Preferred Recurrence-Interval and Vertical Slip-Rate Estimates – Review of Paleoseismic-Trenching Data by the Utah Quaternary Fault Parameters Working Group, by William R. Lund.

This 109-page report in CD format presents the results of a comprehensive evaluation of paleoseismic-trenching data available for Utah’s Quaternary (0 – 1.8 million years old) faults by the Utah Quaternary Fault Parameters Working Group, a panel of experts convened by the UGS in 2003-04. Trenching data are available for 33 (16%) of Utah’s 212 Quaternary faults and fault sections.

Where the data permitted, the Working Group assigned consensus preferred recurrence-interval and vertical slip-rate estimates for these faults. These estimates are necessary to (1) update the U.S. Geological Survey’s National Seismic-Hazard Maps, (2) characterize seismic sources, (3) perform probabilistic seismic-hazard analyses, and (4) provide data for research into other earthquake topics.

This publication discusses the geologic characteristics of the faults, provides details of the paleoseismic investigations conducted, and considers adequacy and uncertainty of existing paleoseismic-trenching data. The data available for the 33 faults/fault sections varies, with the most abundant information on the six central segments of the Wasatch fault zone.

Due to gaps in the paleoseismic information available for Utah, the Working Group recommends additional study of 20 faults/fault sections to characterize Utah’s earthquake hazard to a minimally acceptable level.

The work of the Utah Quaternary Fault Parameters Working Group, headed by Lund, will receive a 2005 Western States Seismic Policy Council Award in Excellence for Research Projects at their annual meeting in Boise, Idaho on September 14, 2005. Lund also received the 2005 UGS Crawford Award for outstanding contributions to the understanding of Utah geology for this publication.

Bulletin 134 is available at the Natural Resources Map & Bookstore, 1594 West North Temple, Salt Lake City (801-537-3320 or 1-888-UTAHMAP; http://mapstore.utah.gov) at a cost of $19.95. For additional information about the report, contact Bill Lund at (435) 865-9034, billlund@utah.gov.