Last year's 5.8 magnitude earthquake in Mineral, Virginia, was felt over an area much larger than previously thought. In a new study, scientists with the U.S. Geological Survey report landslides triggered by the quake four times farther away from the epicenter, and over an area 20 times larger than expected, based on studies of other earthquakes around the world.

While earthquakes are less frequent in the eastern portion of the United States than in the West, their effects extend over a much larger area. That is due, in part, to the underlying geology of the region, which allows seismic waves to travel farther without being weakened by encounters with faults and plate boundaries.

Randall Jibson and Edwin Harp drove outward from the epicenter area in the weeks after the quake, stopping frequently to examine rocks and steep slopes until they reached the apparent limit of landslides. The farthest effect was seen 245 kilometers away. Previous 5.8 magnitude temblors caused landslides no more than 60 kilometers out.

The researchers say that with the new data about the power of East Coast earthquakes, officials will be able to refine their hazard and risk assessments, and improve emergency preparedness.