Liquefaction-induced ground displacement mapping for the Salt Lake Valley, Utah

This paper presents liquefaction-induced lateral spread and ground settlement maps for the Salt Lake Valley for a M7.0 scenario event on the Wasatch fault and for two probabilistic-based events: (1) peak ground acceleration associated with a 2 percent probability of exceedance in 50 years and (2) peak ground acceleration associated with a 10 percent probability of exceedance in 50 years. The maps presented herein are the first liquefaction-induced ground failure maps developed for Utah using both geotechnical and geological data in conjunction with deterministic and probabilistic estimates of strong motion. These maps have been developed to aid engineers, developers and city planners identify areas that may require additional geotechnical evaluations and/or liquefaction mitigation to reduce the liquefaction hazard. The maps were developed from an extensive geotechnical database, geologic mapping and hazard calculations. Estimates of lateral spread displacement were calculated from the Youd and others regression model and ground settlement estimates were calculated from procedures developed by Tokimatsu and Seed, and Yoshimine and others. Estimates from these methods were plotted within their respective surficial geologic units, and the mapped units were subsequently assigned an estimate of ground displacement based on statistical analysis. The mapped units for the scenario event were assigned a displacement hazard that has an 85 percent probability of nonexceedance for the M7.0 Wasatch fault characteristic earthquake while the probabilistic-based events were assigned the median displacement hazard for their respective probabilistic events. The maps show relatively high lateral spread and settlement hazards exist along and near the Jordan River and in recent alluvial/river/stream/lake deposits found in the northern part of the Salt Lake Valley.