A GEOPHYSICAL STUDY OF THE MAUNIE FAULT IN THE WABASH VALLEY FAULT ZONE

SEXTON, J.L., SMITH, M., MUELLER, S.E., MCCLAIN,J., Department of Geology, Southern Illinois University, Carbondale, IL 62901, sexton@geo.siu.edu.

The Wabash Valley fault zone is located near the eastern edge of the Illinois basin. It extends approximately 55 miles in a northeasterly direction from the Cottage Grove and Shawneetown-Rough Creek fault zones of southern Illinois and western Kentucky and it terminates in southeastern Indiana. Faults within the Wabash Valley area have been shown to be caused by reactivation of ancient Precambrian basement faults. Recent research indicates that movement on several faults occurred in the Holocene. Also earthquake activity occurs in the area near the faults. The research reported here utilizes seismic reflection data, borehole data, and new georadar data to study the Maunie fault, located near Maunie , Illinois. The georadar and shallow seismic surveys have imaged numerous small structures in the shallow sediments near the deeper expression of the Maunie fault. These structures include normal and reverse faults, grabens, folds, and paleochannels. These results indicate that, as with the previously studied faults in the Wabash Valley area, the Maunie fault appears to have been active in Holocene times. This is important for earthquake hazard studies of the region.