Natural Seismicity in and around the Rome Trough, Eastern Kentucky, from a Temporary Seismic Network

Abstract

Abstract The Rome trough is a northeast-trending graben system extending from eastern Kentucky northeastward across West Virginia and Pennsylvania into southern New York. The oil and gas potential of a formation deep in the trough, the Rogersville shale, which is ∼1  km above Precambrian basement, is being tested in eastern Kentucky. Because induced seismicity can occur from fracking formations in close proximity to basement, a temporary seismic network was deployed along the trend of the Rome trough from June 2015 through May 2019 to characterize natural seismicity. Using empirical noise models and theoretical Brune sources, minimum detectable magnitudes, Mmin, were estimated in the study area. The temporary stations reduced Mmin by an estimated 0.3–0.8 magnitude units in the vicinity of wastewater-injection wells and deep oil and gas wells testing the Rogersville shale. The first 3 yr of seismicity detected and located in the study area has been compiled. Consistent with the long-term seismicity patterns in the Advanced National Seismic System Comprehensive Catalog, very few earthquakes occurred in the crust beneath the Rome trough—only three events were recorded—where the temporary network was most sensitive. None of these events appear to have been associated with Rogersville shale oil and gas test wells. Outside of the trough boundary faults, earthquakes are diffusely distributed in zones extending into southern Ohio to the north, and into the eastern Tennessee seismic zone to the south. The orientations of P axes from the seven first-motion focal mechanisms determined in this study are nearly parallel with both the trend of the Rome trough and with the orientation of maximum horizontal compressive stress in the region. This apparent alignment between the regional stress field and the strikes of faults in the trough at seismogenic depths may explain the relative lack of earthquake activity in the trough compared with the surrounding crust to the north and south.