Regional Mesozoic Structure and Active Seismicity in Southeastern North America

Erin R. Derrick
University of South Carolina

A revised regional structural and tectonic interpretation of the buried Mesozoic basins of southeastern North America suggests that seismicity in the Middleton Place-Summerville Seismic Zone near Charleston, South Carolina can be related to specific and predictable fault geometries linked to the South Georgia Rift. Examination of the recorded seismicity in this area indicates a pattern consistent with SGR basin under a compressional stress regime, characterized by NW-striking sub-vertical faults and NE-striking, NW-dipping reverse faults. Twenty-four historic events, ranging in magnitude from 0.5 M to 3 M, define a linear trend ~12 km long striking ~N60°W. The only reliable focal mechanism determined for this population of events suggests left-lateral strikeslip movement on a high-angle NW-striking fault system, which we define as the Lincolnville Fault. A seismic refraction experiment is planned to determine a more exact location and displacement across this proposed fault. In addition, 39 recorded historic microearthquakes (between 1 M and 3 M) in the study area appear to define a NE-striking, NW-dipping plane we define as the Fort Dorchester Fault. Previous studies have related seismicity in the Middleton Place-Summerville Seismic Zone to reactivation of Mesozoic extensional structures, but this study is the first to place these within a well-constrained structural and tectonic framework for the South Georgia Rift, and may provide a better model for understanding intraplate seismicity in general.

AAPG Search and Discovery Article #90182©2013 AAPG/SEG Student Expo, Houston, Texas, September 16-17, 2013