Linking Observed Seismicity to Crustal Structure in the New Madrid Seismic Zone Using Gravity and Magnetic Modeling

Abstract

The New Madrid Seismic Zone in the Central United States is a highly active seismic zone. Research has focused on the subsurface structure and history of development in order to gain better insight into the cause of these intraplate earthquakes. Geophysical and geologic data were incorporated to create crustal models along a transect in the New Madrid Seismic Zone (NMSZ) to gain a better understanding of the deep structure of the region and its relationship to potential sources of prehistoric earthquakes. A comprehensive database consisting of LiDAR data, geologic data, well-log information, and locations of liquefaction deposits was assembled in ESRI ArcGIS™ to provide a framework for interpreting the gravity and magnetic data. Potential field analyses identified prominent features in the region that occur in close proximity to the locations of earthquakes. Large anomalies are interpreted as igneous intrusions that vary laterally in composition. Prominent lineations in the data highlight the rift margins and Reelfoot fault. For this study, two transects were chosen to cross key features identified from potential field observations. The models indicate a large mafic body beneath the region that shows a spatial correlation with areas of high seismicity, suggesting that this body is controlling the high seismicity in the region.