Paleoseismology of the southeastern Reelfoot Rift in western Tennessee and implications for intraplate fault zone evolution

The southeastern Reelfoot Rift margin is expressed as a series of collinear scarps across western Tennessee, and shallow S wave reflection profiles, coring, and trenches show late Quaternary faulting along this lineament. At the north end, our seismic profile and coring suggest ≥1.5 m of Wisconsin down-to-the-NW faulting. Coring and trenches across the central lineament show ≥3 m of up-to-the-NW and 8-15 m of right-lateral Late Wisconsin/Holocene faulting. Averaged late Quaternary right-lateral slip has been 0.85-0.37 mm/yr on one fault plane at this locality, suggesting that total slip across all southeast rift margin fault planes may accommodate much of the regional strain. Our seismic profile at this site shows up-to-the-west faulting of Eocene strata folded down-to-the-west, indicating structural inversion. Seismic profiles, electrical surveys, coring, and a trench across the southern lineament segment show Holocene faulting. Trenching exposed a vertical fault with ∼0.5 m of late Holocene down-to-the-NW displacement. Nearby, coring and electrical surveys show ∼0.5 m of late Holocene up-to-the-NW faulting. We conclude the southeastern Reelfoot Rift margin is a right-lateral system with high-angle faults showing both up-to-the-NW and down-to-the-NW separations. Age constraints permit an earthquake circa 2500 to 2000 years B.P. on the southwestern/central segment of this fault system that ruptured ≥80 km. We suggest the northeastern segment of the southeastern rift margin turned off in Holocene when the Reelfoot step over thrust turned on. Copyright 2006 by the American Geophysical Union