AN ASSESSMENT OF FAULTING BENEATH SHELBY COUNTY, TENNESSEE

Shelby County, Tennessee is potentially one of America's most hazardous regions due to its location immediately southeast of the New Madrid seismic zone. Previous investigators identified earthquake liquefaction and faulting within southern Shelby County. These investigators mapped subsurface down-to-the-west northeast striking, and down-to-the-north east-west striking faults. This current investigation has expanded upon the previous studies to include all of Shelby County. Subsurface data consists of geotechnical borings and water well logs. Approximately 1100, 10-27 m deep geotechnical borings and 750, 20-167 m deep water well logs were examined for stratigraphic picks, consequently creating a point density of 0.72 data points per km² for the Pliocene Upland Complex surface, 0.45 data points per km² for the Eocene Upper Claiborne surface, and 0.29 data points per km² for the Eocene Lower Claiborne surface. Using these datasets, structure contour maps were constructed of the tops of the Upland Complex, Upper Claiborne Group, and Lower Claiborne Group (Memphis Sand). Isopach maps were made of the Pleistocene Loess, the Upland Complex, and the Upper Claiborne Group. These maps allow us to (1) assess the existence of previously identified Quaternary faults in Shelby County; (2) determine if the faults in the southern portion of the county extend into the northern portion of Shelby County; and (3) provide a 3-D model of the subsurface geology of Shelby County that will address both potential earthquake and groundwater concerns.