Seismogenic Crustal Stress in Intraplate North America: Slip Potential of Suspected Quaternary Faults in the Central and Eastern United States

Abstract Eastern North America has experienced numerous major tectonic events, which have left behind faults of many different orientations. The modern seismogenic potential of these faults depends chiefly on their orientations relative to the local crustal stress field. Here, earthquake focal mechanisms are used to map seismogenic stress across eastern North America. There are large variations, from east-northeast compression and reverse faulting along the Atlantic coast, through transpression and strike slip in the Midcontinent, to trans-tension with widely varying extension directions on the Great Plains, plus important second-order variations. Against this heterogeneous backdrop, the slip potential of 61 suspected Quaternary tectonic features is then quantified in terms of normalized instability and Coulomb failure stress gradient. These analyses provide insight into whether the proposed faults and senses of slip comport with local stress, or if a nontectonic origin for the features is more likely. Of the 61 features, 15 are deemed incompatible with the modern stress field, 7 are misaligned for slip but uncertainties in fault geometry or stress prevent their being ruled out, 10 are suitable for slip but not optimally oriented, 25 are optimally oriented, and there is insufficient information for the remaining four. Slip potential quantification is extended to mapped geologic faults surrounding the features to identify candidate faults for historical earthquakes (e.g., 1886 Charleston, South Carolina; 1727 Newburyport, Massachusetts) or instrumental seismicity (e.g., Moodus, Connecticut; Wabash Valley Seismic Zone), or to highlight regional optimally oriented faults that may slip in future earthquakes (e.g., Ramapo fault system, New Jersey). This new information may aid in interpreting historical accounts, prioritizing paleoseismic targets, and understanding fault-system behavior.