Geophysical and geological analysis of fault activity and seismic history of the Obion River Area, New Madrid Seismic Zone (NMSZ), Western Tennessee, USA

Abstract

The New Madrid Seismic Zone (NMSZ) is well known for producing some of the largest intra-cratonic earthquakes within the North American Plate. The common hypothesis for the geological structure within the NMSZ is that stress is released across three major faults: the Cottonwood Grove Fault, the New Madrid North Fault, and the Reelfoot Thrust Fault. Evidence exists that would suggest an alternative model of geologic deformation in the area: that stress is being released across more than these three faults. A geologic and geophysical investigation was done to investigate a hypothetical fault west of Dyersburg, TN to test the alternative multi-fault hypothesis. A seismically created sand blow was logged in close proximity to the fault projection. Weathering of the sand blow indicated that the age of the sand blow came from a seismic event prior to the 1811-1812 earthquakes. There was no evidence to confirm this sand blow was created by a hypothetical fault in close proximity. A seismic exploration of the area was done across four seismic lines, primarily mapping Quaternary-age Mississippi River flood plain deposits. These seismic surveys yielded no evidence to suggest the presence of an additional fault. Across all surveys no evidence was found to conclusively support any existing theory on fault movement in the NMSZ.