IMPLICATIONS OF NEW DATA ON SURFICIAL QUATERNARY THRUST FAULTING NEAR VONORE, TENNESSEE, IN THE EASTERN TENNESSEE SEISMIC ZONE (Invited Presentation)

The northeast-trending Eastern Tennessee seismic zone (ETSZ) has the second highest rate of seismic energy release in eastern North America. Recent field studies have revealed a northeast-trending corridor of surficial Quaternary faults within the ETSZ. We report results of new excavations at the outcrop of one of these faults near Vonore, Tennessee. The “Vonore thrust” is located at 35.6266°, -84.217°, within the most seismically active portion of the ETSZ. The thrust fault is exposed in the walls of an east/west-trending drainage ditch and can be traced vertically up the higher north wall for 5 m. The thrust strikes 057^o, dips 77^oSE, and places Middle Cambrian Rogersville Shale saprolite over Quaternary gravel-bearing sediment that has an OSL age of 134.7 ± 10.7 ka. Bedrock saprolite is brecciated within a 0.5 m-wide shear zone along the fault, and the contact between in situ bedrock and fault zone breccia is sharp. Down-dip slickenlines on surfaces within the zone of shearing indicate north vergence. The depositional contact between Quaternary sediment and Rogersville saprolite is below the drainage ditch floor on the footwall of the thrust, and the height of this contact in the hanging wall of the thrust constrains dip slip to be at least 3 m. If this amount of fault throw developed during one event, the basement fault system that produced the Vonore thrust and a nearby normal fault poses a significant seismic hazard.