LIQUEFACTION SUSCEPTIBILITY AND FAULT MAPPING IN SHELBY COUNTY, TENNESSEE

DEEN, T., and VAN ARSDALE, R., The University of Memphis, Memphis, TN 38125, and HARRIS, J., Millsaps College, Jackson, MS 39210, and WOOLERY, E., University of Kentucky, Lexington, KY 40506, tdeen@memphis.edu, rvanrsdl@memphis.edu, harrijb@millsaps.edu; woolery@uky.edu.

Earthquake liquefaction is limited to Holocene river flood plains in the city of Memphis and Shelby County, Tennessee. However, liquefaction susceptibility varied among the streams and appears to have been controlled by variations in flood plain stratigraphies. Three streams flow westerly across Shelby County and the city of Memphis. Earthquake induced sand dikes, probably dating to the great New Madrid earthquakes of 1811-1812, have been identified within the flood plain of the Wolf River throughout Shelby County and at the mouth of the Loosahatchie River. Nonconnah Creek does not have sand dikes. Thus, development is not threatened by earthquake liquefaction on the Nonconnah Creek flood plain, but is a concern on the Wolf and Loosahatchie flood plains. Three N30E trending faults have been identified beneath Shelby County from drill hole and seismic reflection data. Two of the faults have 20m of down-to-the-west displacement on the Pliocene Upland gravel (Lafayette gravel). The third fault has displacement of 5m, but appears responsible for creating an anticline during strike slip offset. The anticline is exposed in the north bank of the Wolf River and has been seismically imaged to a depth of 60m within the Eocene Lower Claiborne Group. This anticline has an amplitude of 4m, a wave length of 100m, and formed in approximately 400 A.D. Work is in progress to determine if there has been surface Holocene fault displacement on the three faults.