Finding Fault in Dyer County, Tennessee: Exploring the Relationships of Earthquake-Induced Liquefaction Features to Subsurface Faults

Abstract

The New Madrid Seismic Zone (NMSZ) is located within the northern Mississippi Embayment, a northeast-striking graben that formed as a part of a failed rift system and later filled with sediments. Although this intracontinental region exhibits mostly low-magnitude seismicity today, the region experienced three large earthquake sequences (M >7) in 1811-1812. Seismic sources of the seismicity in the NMSZ are recognized by patterns of earthquake epicenters; however, surface evidence of these structures is lacking. This study is aimed at identifying seismogenic faults responsible for the earthquake-induced liquefaction features found at a site in western Tennessee. Two near-surface seismic reflection profiles, chosen to cross sand blows found at the site, were collected for this study. The new seismic reflection data reveal near-surface deformation consistent with the presence of the earthquake-induced liquefaction deposits, but lack evidence for shallow faulting beneath the site. Rather, deformation observed in the seismic lines is consistent with lateral spreading that may have occurred during an episode of strong ground shaking. The trend of liquefaction features, however, is parallel to a system of northeast-southwest-trending faults and supports the interpretation that the subsurface deformation seen in the reflection data may reflect active faulting nearby.