Geophysical and Geological Evidence of Neotectonic Deformation along the Hovey Lake Fault, Lower Wabash Valley Fault System, Central United States

摘要

High-resolution seismic (shear-wave) reflection profiles were collected over a segment of the Hovey Lake fault, a known Paleozoic fault within a system of faults in the southernmost Wabash River valley of the central United States. Although the fault zone, called the Wabash Valley fault system, lies in an area of recognized prehistoric and contemporary seismicity, the seismogenic potential of this system remains poorly defined. Consequently, the objectives of this study are to assess the Hovey Lake fault, one of the more prominent fault strands in the system, for neotectonic reactivation and if present, collect sediment samples for dateable material from the disrupted horizons to provide an age constraint for the movement. The resultant stacked profiles show high-angle deformation extending above the Paleozoic bedrock and into Upper Quaternary sediment. Time-displacement calculations from the data show approximately 10.5 m of offset on the top-of-bedrock horizon and 2 m of inverted displacement along the earliest-arriving Quaternary soil reflector. Preliminary correlative coring and carbon-14 age dating of a disrupted soil horizon, located 7.7 m below ground surface, suggest fault movement at this site as late as approximately 37,000 years before present.