Oral Presentation

A PROPOSED METHOD FOR DETERMINING THE OFFSHORE PRESENCE AND EXTENT OF THE ASHLEY RIVER FAULT NEAR CHARLESTON, SOUTH CAROLINA

Jack D. May, Department of Geological Sciences, University of South Carolina, 701 Sumter Street, EWSC Room #501, Columbia, South Carolina, 29208, (E-mail: jmay@seis.sc.edu).

The Ashley River Fault (ARF) near Charleston, South Carolina, has been established as seismically active, having experienced movement during and since the 1886 Charleston earthquake. Based on seismicity, and macroscopic data from the 1886 earthquake the ARF trends northwest to southeast along the Ashley River for about 30 km from near Summerville to Magnolia Gardens. Its southeastern extent has not yet been established, but it has been suggested that it may extend seaward. It has been further hypothesized that the ARF may be an extension of the Blake Spur Fracture (BSF). Here I describe a technique that has been applied off the coast of California that may be able to bridge the gap between the AFR and BSF. Off the coast of California, on the Southern California Continental Borderland, single beam, dual frequency (3.5 and 10 kHz) acoustic profiles were obtained to determine sediment thickness in the area. The 3.5 kHz was shown to effectively penetrate overlying sediment, allowing for visualization of the sediment-hard rock interface. This, in turn, allowed for the delineation of several area faults thought to be active in the last 5 million years. It is believed that if a similar survey, using this technique, were conducted offshore of South Carolina, the presence and extent of the ARF could be ascertained and its possible link with the BSF determined.

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