THE ROME TROUGH: A SEISMICALLY QUIESCENT INTRAPLATE RIFT BOUNDING ACTIVE SEISMIC ZONES

The Rome Trough, a northeast-trending graben system extending from eastern Kentucky across West Virginia and Pennsylvania into southern New York, is part of a larger, failed, intraplate rift system. Although the Trough is heavily faulted, the historical earthquake catalog shows that it has hosted very few earthquakes, contrasting with active earthquake zones to the north of the Trough and to the Trough’s south, which includes the Eastern Tennessee Seismic Zone. Using recordings from a temporary seismic monitoring project in eastern Kentucky and template-matching of natural- and induced-earthquakes recorded by regional stations, we produced a high-resolution catalog of earthquakes in and near the Rome Trough. Consistent with the historical seismicity patterns, very few earthquakes occurred in the crust beneath the Trough, most of which were near the Trough’s boundary faults. One possible explanation for this seismic quiescence is that the faults within the Trough are not optimally oriented for movement in the current regional stress field. To investigate this possibility, we refined and updated the basement fault maps in and around the Rome Trough into southern Pennsylvania and compiled both new regional stress data and what was available in the World Stress Map database for the same region. SH_max orientations from 27 data points within or near the Trough boundaries yield an average σ₁ azimuth of 57°. Geologic materials under confining pressure tend to shear at ±30° from the σ₁ direction. Therefore, faults in this strike-slip regime trending near either 27° or 87° azimuth would be preferentially oriented for slip. However, because the Rome Trough border faults and the vast majority of internal faults trend between azimuths of 45° and 70°, they are not likely to slip in the current regional stress field.