3D GEOLOGIC MAPPING IN AND ADJACENT TO THE NEW MADRID SEISMIC ZONE, CENTRAL UNITED STATES

A five-year seismic and liquefaction hazard mapping project for five western Tennessee counties in and immediately east of the New Madrid seismic zone began in 2017 under a Disaster Resilience Competition grant from the U.S. Department of Housing and Urban Development to the State of Tennessee. Geological, geotechnical, and geophysical information were gathered in Lake, Dyer, Lauderdale, Tipton, and Madison (in progress) counties to improve existing earthquake hazard maps. Compiled information includes geological and geotechnical subsurface exploration logs, seismic reflection data, water table level data, new measurements of shallow and deep shear-wave velocity (Vs) profiles, and the compilation of existing Vs profiles in and around the counties. A 3D geological model, water table model, geotechnical liquefaction probability curves, and Vs correlation with lithology models were generated for each county. Here we present the 3D geology of Lake, Dyer, Lauderdale, and Tipton counties. The 3D county models provide stratigraphic thicknesses necessary for ground motion assessment given specified earthquake scenarios and reveal faults that should be studied for Quaternary displacement. Sediment types and thicknesses in saturated floodplain alluvium also illustrate where surface overbank silt/clay thickness may influence liquefaction in future earthquakes.