Seismic and Liquefaction Hazard Maps for Five Western Tennessee Counties

A five-year seismic and liquefaction hazard mapping project for five western Tennessee counties began in 2017 and supported natural hazard mitigation efforts in Lake, Dyer, Lauderdale, Tipton, and Madison counties. Additional geological, geotechnical, and geophysical information has been gathered in all five counties to improve the base northern Mississippi Embayment hazard maps of Dhar and Cramer (2017). Information gathered includes additional geological and geotechnical subsurface exploration logs, water table level data collection, new measurements of shallow shear-wave velocity (VS) profiles, and the compilation of existing VS profiles in and around the counties. Improvements have been made in the 3D geological model, water table model, the geotechnical liquefaction probability curves, and the VS correlation with lithology model for these counties. The resulting updated soil response amplification distributions on a 0.5 km grid were combined with the 2014 U.S. Geological Survey seismic hazard model (Petersen et al., 2014) earthquake sources and attenuation models to add the effect of local geology for Lake, Dyer, Lauderdale, Tipton, and Madison Counties. The resulting products are similar to the Memphis and Shelby County urban seismic hazard maps recently updated by Cramer, Dhar, and Arellano (2018). Generally, the effect of local geology is to reduce seismic hazard at short periods and increase it at long periods. Liquefaction hazard is high only in the alluvial lowlands, but not in the loess covered uplands.

Automated summary

A five-year project supported natural hazard mitigation efforts in five western Tennessee counties by improving the hazard maps and adding the effect of local geology. The project gathered additional geological, geotechnical, and geophysical information and made improvements in the geological model, water table model, liquefaction probability curves, and velocity correlation with lithology model. The resulting updated soil response amplification distributions were combined with seismic hazard models to consider the local geology.