PALEOSEISMIC INDICATORS NEAR BLUFFTON, SOUTH-CAROLINA - AN APPRAISAL OF THEIR TECTONIC IMPLICATIONS

Radiocarbon dating of paleoliquefaction features near Bluffton in Beau fort County, South Carolina, indicates a likelihood of four prehistori c seismic events that occurred at 500 +/-180, 1180 +/-220, 2355 +/-365 , and 3355 +/-485 yr B.P. Among these, the 500 +/-180 and 2355 +/-365 yr B.P. events appear to have originated near Bluffton, outside of the currently active Charleston seismic source zone. Association of these two events with a local source near Bluffton conflicts with the idea of periodic activation of a single seismic source near Charleston. The felt shocks of 1826, 1903, and 1912, reported from approximately 20 k m south of the paleoliquefaction sites, and a small earthquake on Janu ary 1989 located near Bluffton indicate that this area has been modera tely active in historic times. Releveling data have identified an appr oximately 30-km-long zone of uplift in the area. Stratigraphic data in dicate the presence of an east-trending buried fault in the vicinity. These observations imply the presence of an additional seismic source zone in the South Carolina coastal lain near Bluffton.