Investigating seismotectonics in the eastern United States using a geographic information system

In the central and eastern U.S. (CEUS) the assessment of seismic hazard is problematic because the active tectonic features are generally not identified. Many ideas have been proposed to explain why earthquakes occur in the CEUS and which geologic structures are associated with the earthquakes. Earthquakes in the CEUS have been attributed to postglacial rebound, the reactivation of preexisting zones of weakness in the continental crust near extensions of oceanic fracture zones, stress concentrations associated with mafic/ultramafic plutonic masses, intersections of major structural features in the crust, reactivation of previously rifted crust, present-day faulting along lapetan margin faults, and hydroseismicity. It is possible that many, if not all, of these hypotheses proposed to explain the spatial distribution of earthquakes in the CEUS and to identify potentially active geologic features has some merit, and it is possible that many or all of them are operative in some way in the CEUS. In this study we constructed a GIS database of earthquake, geological and geophysical data, and we used that database to study the correlation of the seismicity with the geology and tectonics of the CEUS. Using earthquake, geological and geophysical parameters derived from this GIS database, we carried out statistical analyses to try to identify seismically active features in the CEUS. We limited our research to the most seismically active areas in the CEUS, namely: (1) the seismically active area of the Appalachians and east coast, from Maine to Georgia, (2) the broadly active region around the New Madrid seismic zone (Illinois and Indiana to Arkansas and Mississippi), and (3) the broad area of low activity throughout Kentucky and Ohio. In our statistical analyses we looked for common geological and geophysical features associated with the seismic activity on a regional basis throughout this study region

First Results of the Regional Earthquake Likelihood Models Experiment

The ability to successfully predict the future behavior of a system is a strong indication that the system is well understood. Certainly many details of the earthquake system remain obscure, but several hypotheses related to earthquake occurrence and seismic hazard have been proffered, and predicting earthquake behavior is a worthy goal and demanded by society. Along these lines, one of the primary objectives of the Regional Earthquake Likelihood Models (RELM) working group was to formalize earthquake occurrence hypotheses in the form of prospective earthquake rate forecasts in California. RELM members, working in small research groups, developed more than a dozen 5-year forecasts; they also outlined a performance evaluation method and provided a conceptual description of a Testing Center in which to perform predictability experiments. Subsequently, researchers working within the Collaboratory for the Study of Earthquake Predictability (CSEP) have begun implementing Testing Centers in different locations worldwide, and the RELM predictability experiment—a truly prospective earthquake prediction effort—is underway within the U.S. branch of CSEP. The experiment, designed to compare time-invariant 5-year earthquake rate forecasts, is now approximately halfway to its completion. In this paper, we describe the models under evaluation and present, for the first time, preliminary results of this unique experiment. While these results are preliminary—the forecasts were meant for an application of 5 years—we find interesting results: most of the models are consistent with the observation and one model forecasts the distribution of earthquakes best. We discuss the observed sample of target earthquakes in the context of historical seismicity within the testing region, highlight potential pitfalls of the current tests, and suggest plans for future revisions to experiments such as this one.ISSN:0033-4553ISSN:1420-9136ISSN:1557-736

Tofacitinib in Combination With Methotrexate in Patients With Rheumatoid Arthritis: Clinical Efficacy, Radiographic, and Safety Outcomes From a Twenty-Four-Month, Phase III Study

Pathophysiology and treatment of rheumatic disease