NEAR-SURFACE STRUCTURAL MODEL FOR DEFORMATION ASSOCIATED WITH THE FEBRUARY 7, 1812, NEW MADRID, MISSOURI, EARTHQUAKE

The February 7, 1812, New Madrid, Missouri, earthquake (M [moment magn itude] 8) was the third and final large-magnitude event to rock the no rthern Mississippi Embayment during the winter of 1811-1812, Although ground shaking was so strong that it rang church bells, stopped clocks , buckled pavement, and rocked buildings up and down the eastern seabo ard, little coseismic surface deformation exists today in the New Madr id area. The fault(s) that ruptured during this event have remained en igmatic. We have integrated geomorphic data documenting differential s urficial deformation (supplemented by historical accounts of surficial deformation and earthquake-induced Mississippi River waterfalls and r apids) with the interpretation of existing and recently acquired seism ic reflection data, to develop a tectonic model of the near-surface st ructures in the New Madrid, Missouri, area, This model consists of two primary components: a north-northwest-trending thrust fault and a ser ies of northeast-trending, strike-slip, tear faults, We conclude that the Reelfoot fault is a thrust fault that is at least 30 km long. We a lso infer that tear faults in the near surface partitioned the hanging wall into subparallel blocks that have undergone differential displac ement during episodes of faulting, The northeast-trending tear faults bound an area documented to have been uplifted at least 0.5 m during t he February 7, 1812, earthquake. These faults also appear to bound cha nges in the surface density of epicenters that are within the modern s eismicity, which is occurring in the stepover zone of the Left-steppin g right-lateral strike-slip fault system of the modern New Madrid seis mic zone.