Why Was The Virginia Quake Felt So Far Away?

The 5.8 magnitude earthquake that occurred in Virginia was felt all over the East Coast, from Boston to North Carolina, and even as far away as Milwaukee, Wisconsin.

Although the magnitude of the Virginia earthquake was not exceptionally large, it was still felt a significant distance away. Earthquakes that occur on the east side of the Rocky Mountains can be felt up to ten times farther away from the epicenter than earthquakes of a similar magnitude that happen on West Coast faults.  Why is this? According to the United States Geological Survey (USGS), this is because of the difference in the types of rocks between the east and west coasts. 

Callan Bentley, assistant professor of geology at Northern Virginia Community College, explains that rock on the east coast is denser and colder, and therefore transmits seismic waves more efficiently than the rock on the west coast.  The large number of fractures in Earth’s crust on the West Coast also prevent the seismic waves from traveling great distances.

Fortunately, it doesn’t appear that the quake caused major damage.  Large earthquakes in this region are fairly rare.  The August 23, 2011 5.8 magnitude earthquake is the strongest ever recorded in the Central Virginia Seismic Zone, and the second largest earthquake ever recorded in the in the state of Virginia.  The largest quake happened in 1897, when a 5.9 magnitude earthquake struck in Giles County.

Sources:

http://www.earthmagazine.org/earth/article/474-7db-8-17

http://latimesblogs.latimes.com/nationnow/2011/08/earthquake-is-strongest-in-central-virginia-history-expert-says.html

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