EVALUATING THE REGIONAL SCALE POTENTIAL FOR (INDUCED?) SEISMICITY IN THE NORTHERN APPALACHIAN BASIN AND THE NORTHEASTERN US AND SOUTHEASTERN CANADA FROM POTENTIAL FIELDS, SEISMICITY, AND THE WORLD STRESS MAP

Two recent related efforts have evaluated the potential for (possibly induced) seismicity in Northern portions of the Appalachian Basin and in the NE US/SE Canada. We evaluated whether a candidate location is near an active fault, and thereby potentially susceptible to induced seismicity from geothermal operations. Existing fault maps do not share our boundaries or scale, and they lack basic information on structures in crystalline basement beneath the Appalachian basin. Hence, their use leads to problems of uneven coverage, varying interpretation of faults vs. lineaments, and different mapping scales.

Analyses of gravity and magnetic fields affords not only the uniformity of coverage, but, after calibration with independent data sets, it enables structural analyses beneath thick sedimentary cover. Multiscale-edge Poisson wavelet analyses of potential fields ("worms") have a physical interpretation as the locations of lateral boundaries in a source distribution that exactly generates the observed field. Not all worms are faults, and of faults, only a subset might be active. Also, worms are only sensitive to steeply dipping structures. To identify some active structures, we plot worms and intraplate earthquakes from the NEIC, and EarthScope TA catalogs. Worms within a small distance of epicenters are tracked spatially. To within errors in location, this is a sufficient condition to identify structures that might be active faults, which we categorize with higher risk than other structures.

Plotting worms within World Stress Map σ₁ directions yields an alternative approach to identifying structures most likely to be reactivated. Here, we use worms to identify structures with strikes favorably oriented for failure by Byerlee's law. While this might be a necessary criterion for fault activation it is not a sufficient one, owing to the lack of detailed information about stress magnitudes throughout the region.