Explanation found for 2011 earthquake on US East Coast

Gizmodo : The magnitude 5.8 earthquake that struck northern Virginia in 2011 was notable because of the extreme rarity of earthquakes in that region—it was the strongest earthquake east of the Rocky Mountains since 1944. The East Coast of the US is far from the edges of the North American tectonic plate, where interactions with neighboring plates trigger seismic activity. Now Berk Biryol of the University of North Carolina at Chapel Hill and colleagues believe they have found an explanation for the 2011 earthquake. Biryol’s team used seismic activity from around the globe to construct a 3D map of the bottom of the North American plate. The researchers found that the southeastern part of the plate is heavily fractured and encompasses thin and thick sections of crust and mantle. Based on their map, the scientists argue that chunks breaking off the bottom of the plate could trigger earthquakes. The mechanism could explain other major seismic events such as the magnitude 8.1 earthquake that struck New Madrid, Missouri, and the 7.0 earthquake that struck Charleston, South Carolina, in the 1800s.