THE USE OF GIS FOR SEISMIC HAZARD ANALYSIS IN THE CHARLESTON SC REGION

Charleston, South Carolina experienced the most damaging earthquake in the Eastern United States. The August 31, 1886 earthquake had a magnitude of 7.3 (Johnson, 1996) and was felt over 2.5 million square miles (From Cuba to New York, and Bermuda to the Mississippi). The earthquake left ninety percent (90%) of the brick structures in Charleston damaged (Dutton, 1889). Earthquake events have been documented in the state since 1698. About seventy percent of these earthquakes are located in the Middleton Place-Summerville Seismic Zone (MPSSZ), 30 kilometers northwest of downtown Charleston. Since 1997, 128 earthquakes have been recorded in the MPSSZ. The risk from a reoccurrence of an earthquake of magnitude 6 or higher within the region is greater now due to changes in land use and population growth. Major hazards due to ground shaking and liquefaction during an 1886 style event could lead to an estimated 14 billion dollars of damage and potentially 900 fatalities with 45,000 injuries. Furthermore, the HAZUS analysis for the region projects extensive infrastructure damage that would complicate relief efforts (URS, 2001). This study concentrates on the use of GIS at the College of Charleston for seismic monitoring and hazard analysis. A GIS system is being implemented for use in planning the emplacement of the Charleston ANSS (Advanced National Seismic System) Urban Strong Motion Center and for modeling seismic hazard in the region. The GIS has already been used in the placement of 4 strong motion stations in the study area. The sites were chosen as being representative of Charleston site conditions (made-land, estuarine deposits, alluvial fill). The GIS will also be used to organize existing shear wave velocity information and plan for future refraction micro-tremor studies to improve knowledge of the shear wave velocity structure in the greater Charleston region. This information will be used to refine the HAZUS analysis and pinpoint areas at the greatest risk