Initial Assessment of the Intensity Distribution of the 2011 Mw 5.8 Mineral, Virginia, Earthquake

Abstract

The intensity data collected by the U.S. Geological Survey (USGS) “Did You Feel It?” (DYFI) Website (USGS, DYFI; http://earthquake.usgs.gov/earthquakes/dyfi/events/se/082311a/us/index.html, last accessed Sept 2011)for the M w 5.8 Mineral, Virginia, earthquake, are unprecedented in their spatial richness and geographical extent. More than 133,000 responses were received during the first week following the earthquake. Although intensity data have traditionally been regarded as imprecise and generally suspect (e.g., Hough, 2000), there is a growing appreciation for the potential utility of spatially rich, systematically determined DYFI data to address key questions in earthquake ground-motions science (Atkinson and Wald, 2007; Hauksson et al. , 2008). DYFI intensities for the Mineral, Virginia, earthquake provide a unique opportunity to explore the variability of wave propagation and site amplification along the Atlantic seaboard of the United States, a region where instrumental recordings of moderate and large earthquakes are limited. The raw DYFI data suggest some general patterns, including not only significant apparent site response along Chesapeake Bay, in parts of the District of Columbia (D.C.), and elsewhere, but also source directivity and more efficient propagation along the predominantly southwest–northeast-striking tectonic fabric. These suggested patterns can be explored further by considering intensity residuals relative to an established intensity ground-motion-prediction equation (e.g., Atkinson and Wald, 2007). The M w 5.8 Mineral, Virginia, earthquake occurred at 17:51:04.59 UTC on 23 August 2011, one of the largest earthquakes in the region in historical times and the largest earthquake to strike the central/eastern United States (CEUS) in 70 yr. Shaking was widely felt through several major metropolitan areas, including the greater Washington, D.C., region, Philadelphia, and parts of New York State. The overall felt extent of the earthquake was enormous, with perceptible shaking reported as far west as Minnesota and as far south as Florida. To the northeast it was …