Working Group on Utah Earthquake Probabilities

The UGS and U.S. Geological Survey (USGS) established the Working Group on Utah Earthquake Probabilities (WGUEP) in 2010 to develop forecasts of large earthquakes along the Wasatch Front. The forecasts were developed with the intention that they would help heighten the public’s awareness and understanding of the region’s seismic hazards, similar to what the forecasts of the Working Group on California Earthquake Probabilities (WGCEP) have successfully done.

The WGUEP employed a methodology similar to that used in the Uniform California Earthquake Rupture Forecast process, implementing a fault model, deformation model, earthquake rate model, and probability model. The WGUEP developed 30-, 50-, and 100-year forecasts that include (1) combined time-dependent and time-independent probabilities of large earthquakes (moment magnitude [M] ≥ 6.75) for the five central segments of the Wasatch fault zone and two segments of the Great Salt Lake fault zone, (2) time-independent probabilities of large earthquakes on 45 less well-studied faults and fault segments, and (3) estimates of the time-independent probabilities of background earthquakes in the M 5.0–6.75 range. Results include 50-year probabilities of 43% for one or more M ≥ 6.75 earthquakes and 57% for one or more M ≥ 6.0 earthquakes occurring within the Wasatch Front region, and 18% for one or more M ≥ 6.75 earthquakes occurring on the Wasatch fault zone.

The final WGUEP report (UGS Miscellaneous Publication 16-3) consists of a 164-page main report as well as five appendices that include a summary of moment magnitude regressions considered by the WGUEP, a comprehensive analysis of paleoseismic data for the central segments of the Wasatch fault zone, and a newly compiled and processed historical and instrumental earthquake catalog for the Wasatch Front and surrounding Utah region.

Partial funding for the WGUEP was provided by the National Earthquake Hazards Reduction Program.

Reports

Earthquake probabilities for the Wasatch Front region in Utah, Idaho, and Wyoming: Utah Geological Survey Miscellaneous Publication 16-3

Earthquake Forecast for the Wasatch Front Region of the Intermountain West: U.S. Geological Survey Fact Sheet 2016–3019 (outside link)

2010-2012 NEHRP Project Report
Working Group on Utah Earthquake Probabilities: Collaborative Research Between the Utah Geological Survey and URS Corporation

Lund, W.R., complier, 2013, Working Group on Utah Earthquake Probabilities preliminary fault characterization parameters for faults common to the working group study area and the U.S. National Seismic Hazard Maps, data provided to the U.S. Geological Survey for use in the 2014 update of the National Seismic Hazard Maps in Utah: Utah Geological Survey Open-File Report 611, 6 p.

Contacts

WGUEP Chair – Ivan Wong, Lettis Consultants International, Inc.; (925) 482-0360, ext. 231; wong@lettisci.com

Mike Hylland, Utah Geological Survey; (801) 537-3382; mikehylland@utah.gov

Chris DuRoss, U.S. Geological Survey; (303) 273-8544; cduross@usgs.gov

UGS Liaison – Steve Bowman; (801) 537-3304; stevebowman@utah.gov