Petroleum exploration seismic reflection profiles in western Tennessee reveal numerous faults within the southeastern margin of the Reelfoot rift. The faults strike from N20E to N50E and are concentrated within a 15 km wide zone. Two down-to-the-west basement faults appear to displace the Precambrian section by ~1 km and ~2.5 km. A number of faults that displace the overlying Paleozoic, Mesozoic, and Tertiary sections lie between these basement faults. Thus, Tertiary faulting in western Tennessee is spatially coincident with, and thus is probably controlled by, Reelfoot rift margin basement faults. Geologic data and seismic reflection profiles near Memphis, Tennessee, reveal Quaternary faults that are also along the southeastern Reelfoot rift margin. Therefore, the total length of Tertiary faulting along this rift margin is >80 km. The NE strike of the rift margin, a mid continent stress field with a horizontal maximum compressive stress oriented N60E, >80 km of Tertiary fault length, and ongoing seismicity suggests that the southeastern Reelfoot rift margin fault zone is capable of generating large earthquakes and is a significant threat to Memphis, Tennessee.