Dr. Frank J Pazzaglia, Lehigh University
About the Seminar
Eastern North America (ENAM) lies in a plate interior where recent seismologic and geomorphic experiments, along with studies of a modest-sized earthquake, are being synthesized into a novel geodynamic model that explains the stress field and makes testable predictions of crustal deformation. Here there is a history of large (M 7), infrequent, and clustered earthquakes. In the context of this seismicity, paleogeodetic geomorphic markers and topographic metrics provide a rare opportunity to quantify the crustal deformation rate and test it against model predictions. The epicenter region of the 2011 M 5.8 Mineral, Virginia earthquake is traversed by the South Anna River. A stratigraphic model of river terraces using OSL, IRSL, and TCN geochronology demonstrates that the long term incision rate in the uplifting hanging wall of the fault is approximately double the incision rate in the subsiding footwall. The terraces are arched up and over the surface projection of the fault plane that has been modeled to have generated ~7 cm of surface deformation distributed over a wavelength consistent with the deformed terraces. Such persistent intraplate seismicity and crustal deformation presents challenges to infrastructure in the eastern US that has not co-evolved with frequent earthquakes.