INVESTIGATING POSSIBLE PALEOSEISMIC EVIDENCE IN THE EAST TENNESSEE SEISMIC ZONE

The greatest concentration of instrumentally recorded earthquakes in the ETSZ occurs near Vonore, Tennessee, ~115 km NE of Chattanooga. Both recent and current research have been focused on searching for paleoseismic features along Tellico Reservoir and the Little Tennessee River which may have been created by large (Mw >6.5) earthquakes in the ETSZ.

Paleoseismic features have been found within a narrow zone that trends NE-SW from Vonore to Maryville, TN. Features that have been found include: red, sandy clay-filled faults and fractures in Quaternary sediment with up to 2 m displacement as well as, similar fractures that cut late Paleozoic structures; inclined Quaternary river strath terrace sediment on Paleozoic bedrock/saprolite; and folded (tectonic?) Quaternary river terrace sediments.

Two major faults were exposed along Tellico Reservoir near Vonore, TN: a NE-striking, SE-dipping red, sandy clay-filled normal fault with ≥ 2 m displacement that placed Quaternary river terrace sediment against Upper Cambrian shale, and faults within an artificial trench on the northeast side of Tellico Lake. The latter exposure consists of Quaternary colluvium in contact with Middle Cambrian deformed shale that is cut by post-Paleozoic faults containing red, sandy clay and breccia-filled fractures that strike NE and dip SE. The main NE-striking, SE-dipping fault of interest is a thrust fault with >1 m displacement and downdip slickenlines.

Additional features that are likely seismogenic and discovered near the two faults include one site with abundant red, sandy clay-filled fractures cutting Middle Cambrian shale saprolite, and Quaternary river terrace folded into an anticline with limbs that dip up to 45°. NW and SE of this zone of deformation paleoseismic features become rare to nonexistent.