SECTION[ SEISMOLOGICAL IRESEARCH LETTERS NORTHERN EXTENSION OF THE TENNESSEE REELFOOT SCARP INTO

he Reelfoot scarp in northwestern Tennessee is the surface expression of an east-verging fault propaga-tion fold that overlies a southwest-dipping reverse fault. This fault is responsible for much of the current New Madrid seismicity and was probably the origin of the Febru-ary 7, 1812, M 8.0 earthquake. Tectonic scarps in the Ken-tucky bend of the Mississippi River and at New Madrid, Missouri, appear to be a northwestern continuation of the Reelfoot scarp. Cores collected across the scarp in Kentucky where the topographic relief is 2.2 m reveal that the structural relief on a distinct subsurface fluvial sand bed is 4 m. One kilometer to the north the topographic relief is 3 m and structural relief is 4 m. Similarly, the scarp at New Madrid, Missouri, has 2 m of topographic and structural relief. These core data re compatible with trench observations to the south where the fold structure is reflected by the surface topography. This northern extension of the Reelfoot scarp into Kentucky and Missouri suggests a mapped length of 32 km, nearly three times its previously defined length of 11 km. This 32 km length is more consistent with, but still too short for, rupture during a M 7.8 or M 8.0 earthquake. Coring data and microearthquake distribution suggest hat the Reelfoot fault/scarp may continue southeast of its presently mapped terminus