DOES THE EASTERN KENTUCKY ROME TROUGH INTERRUPT OR BOUND THE EASTERN TENNESSEE SEISMIC ZONE?

The Rome Trough, a northeast-trending graben system extending from eastern Kentucky northeastward across West Virginia and Pennsylvania into southern New York, is part of a larger failed intracratonic rift system. Seismicity observations from June 2015 through October 2019 from a temporary seismic network—deployed within the boundary faults of the Rome Trough of eastern Kentucky (EKRT)—provide evidence that the EKRT is seismically quiescent compared to the surrounding crust: in the first 39 months of recordings, 160 local earthquakes were detected, but only three earthquakes occurred well within in the crust beneath the EKRT—i.e., more than 5 km from the boundary faults in map view. Outside of the EKRT, earthquakes are diffusely distributed in zones extending into southern Ohio to the north, and into the Eastern Tennessee Seismic Zone to the south. P-axes from seven focal mechanism determined in or near the EKRT are consistent with the mechanisms from larger earthquakes determined both north and south of the EKRT. The P-axes are also consistent with both the orientations of nearby maximum horizontal compressive stress measurements and with the trend of the EKRT. Therefore, if most seismogenic faults of sufficient size to produce detectable earthquakes in the crust beneath the EKRT trend subparallel to the trough’s boundary faults, then they are not favorably oriented for failure in the current stress field. This provides a testable explanation for the seismic quiescence in the crust beneath the EKRT and indicates that the EKRT may be the northern boundary of the Eastern Tennessee Seismic Zone.