Investigating seismotectonics in the eastern United States using a geographic information system

In the central and eastern U.S. (CEUS) the assessment of seismic hazard is problematic because the active tectonic features are generally not identified. Many ideas have been proposed to explain why earthquakes occur in the CEUS and which geologic structures are associated with the earthquakes. Earthquakes in the CEUS have been attributed to postglacial rebound, the reactivation of preexisting zones of weakness in the continental crust near extensions of oceanic fracture zones, stress concentrations associated with mafic/ultramafic plutonic masses, intersections of major structural features in the crust, reactivation of previously rifted crust, present-day faulting along lapetan margin faults, and hydroseismicity. It is possible that many, if not all, of these hypotheses proposed to explain the spatial distribution of earthquakes in the CEUS and to identify potentially active geologic features has some merit, and it is possible that many or all of them are operative in some way in the CEUS. In this study we constructed a GIS database of earthquake, geological and geophysical data, and we used that database to study the correlation of the seismicity with the geology and tectonics of the CEUS. Using earthquake, geological and geophysical parameters derived from this GIS database, we carried out statistical analyses to try to identify seismically active features in the CEUS. We limited our research to the most seismically active areas in the CEUS, namely: (1) the seismically active area of the Appalachians and east coast, from Maine to Georgia, (2) the broadly active region around the New Madrid seismic zone (Illinois and Indiana to Arkansas and Mississippi), and (3) the broad area of low activity throughout Kentucky and Ohio. In our statistical analyses we looked for common geological and geophysical features associated with the seismic activity on a regional basis throughout this study region