HR: 15:25h
AN: S52H-08    [PDF]
TI: The Intersection Model and the Charleston, South Carolina Seismicity
AU: * Talwani, P
EM: talwani@geol.sc.edu
AF: Department of Geological Sciences University of South Carolina, 701 Sumter Street EWSC Building, Columbia, SC 29208 United States
AU: Gangopadhyay, A
EM: abhijit@seis.sc.edu
AF: Department of Geological Sciences University of South Carolina, 701 Sumter Street EWSC Building, Columbia, SC 29208 United States
AU: Dura-Gomez, I
EM: idura@geol.sc.edu
AF: Department of Geological Sciences University of South Carolina, 701 Sumter Street EWSC Building, Columbia, SC 29208 United States
AB: According to the intersection model for intraplate earthquakes, seismicity occurs in the vicinity of suitably oriented (with respect to S$_{Hmax}$) intersecting faults located in weak zones in the crust (such as failed rifts) in response to plate tectonic forces. The intersections are locations where small pockets of stress accumulation occurs, associated with increased strain rates. Support for this model was provided by multidisciplinary data and simple 2-D modeling of the inferred faults associated with the Charleston earthquakes. Seismicity in the Middleton Place Summerville Seismic Zone (MPSSZ) is located at the southern end of the $>$200 km long, NNE trending Woodstock fault where it is cut and offset approximately 5 km by the NW trending Ashley River fault. These faults lie within the South Georgia rift basin. Simple 2-D modeling of blocks bounded by these faults, showed that the largest strain rates are located near the jogs, which are also the locations of intense low-level seismicity. A series of GPS surveys in the 1990s in the MPSSZ and surrounding areas showed the presence of strain zonation. The approximately 600 km$^{2}$ MPSSZ was associated with strain rates of about 10$^{-7}$/year. In the surrounding region with an area of 5000 km$^{2}$, the strain rate was about 10$^{-8}$/year and that outside it is 10$^{-9}$/year compatible with observed values for the North American plate. The results of modeling and GPS surveys - large strain rates in the vicinity of intersecting faults, and the observed seismicity are in accordance with, and provide confirmation of, the intersection model.
DE: 7209 Earthquake dynamics and mechanics
DE: 7230 Seismicity and seismotectonics
DE: 8123 Dynamics, seismotectonics
SC: Seismology [S]
MN: 2003 Fall Meeting