Paleoseismic Evidence for Multiple Mw=6 Earthquakes in the Eastern Tennessee Seismic Zone during the Late Quaternary.

The eastern Tennessee seismic zone (ETSZ) is the second-most active seismic zone in the eastern United States, but it has not generated an earthquake larger than M_w 4.8 in historic time. Earthquakes are sourced deep in autochthonous basement, and there are no known faults originating at this depth that break the surface. As a result, until recently, there has been virtually no fieldwork to identify Quaternary paleoseismic features in the ETSZ. We present new results from paleoseismic investigations of coseismic features that indicate the ETSZ generated M_w=6 earthquakes during the late Quaternary. Detailed geologic mapping and trenching near Dandridge, Tennessee, record a northeast-trending zone of seismically generated features. Optically stimulated luminescence ages delimit timing for the formation of paleoseismic features crosscutting Quaternary alluvium and alluvium-filled fissures, including a thrust fault with ~1 m displacement. Collectively, this zone of faults and fissures provides significant evidence that the ETSZ has produced at least three large earthquakes during the late Pleistocene and at least one that exceeded M_w 6. [ABSTRACT FROM AUTHOR]