HR: 0830h
AN: S21F-0402    [PDF]
TI: High-Resolution Geophysical Investigation of Late Quaternary Deformation in the Lower Wabash Valley Fault System, Central United States.
AU: * Rutledge, F A
EM: f.rutledge@insightbb.com
AF: University of Kentucky, Dept. of Geological Sciences 101 Slone Bldg., Lexington, KY 40506 United States
AU: Woolery, E W
EM: woolery@uky.edu
AF: University of Kentucky, Dept. of Geological Sciences 101 Slone Bldg., Lexington, KY 40506 United States
AU: Wang, Z
EM: zmwang@uky.edu
AF: University of Kentucky, Dept. of Geological Sciences 101 Slone Bldg., Lexington, KY 40506 United States
AU: Wang, Z
EM: zmwang@uky.edu
AF: Kentucky Geological Survey, 221 MMRB, Lexington, KY 40506 United States
AB: High-resolution SH-wave seismic profiles in the lower Wabash Valley Fault System (WVFS) have been used to characterize late Quaternary deformation in the vicinity of the Wabash Island Fault in southern Posey County, Indiana. Seismic images suggest Paleozoic extensional faults have been reactivated by compressional neotectonism. The Quaternary structural inversion is evidenced by pronounced positive folding and displacements in the hanging wall of the primary faults, the broadened deformation area in the nearer surface, and the opposing apparent dip angles in the deformation zone­Ýs fault strands. The geophysical data indicate deformation to within 9 m of the ground surface. A maximum bedrock displacement of $\sim$20 m (across a 200 m fault zone) and a displacement of $\sim$1 m in the earliest arriving reflector was measured along the 2 km profile. Associated drilling and C14 dating of organics found in the disrupted horizons suggest movement between $\sim$26,000 and 42,000 YBP. Although liquefaction, contemporary seismicity, and geodetic measured strain suggest neotectonism in the WVFS from the Pleistocene to present, these images represent the first physical evidence for primary coseismic neotectonism. The identification of seismogenic source structures (i.e., faults) is an integral part of seismic hazard analysis, and can ultimately aid in hazard mitigation.
DE: 1734 Seismology
DE: 1744 Tectonophysics
DE: 7221 Paleoseismology
DE: 7223 Seismic hazard assessment and prediction
DE: 7230 Seismicity and seismotectonics
SC: Seismology [S]
MN: 2003 Fall Meeting