4:00 pm
Tue August 23, 2011

Virginia Quake's Tremors Reach Far

Earthquakes might be rarer on the east coast than they are in the west. But Laura Wagner, assistant professor of seismology at UNC Chapel Hill, explains why tremors here can be felt over such long distances.

Laura Wagner: "There's two parts of it. One is that the underlying rocks on the east coast are very solid, very crystalline, and so waves travel through those really efficiently. So they don't attenuate and lose energy the way they would on the west coast. Then when it comes up through the clay, because the clay here is so weak, the amplitude of the wave gets larger. So that makes it possible for us to feel this so far away."

North Carolinians suddenly finding themselves uneasy about another earthquake like the one felt today can look to history for some comfort. Although Wagner says the likelihood of more earthquakes is hard to predict.

Wagner: "You know, Charleston, South Carolina had a large earthquake, a large 7 shortly after the Civil War, and it hasn't had anything like that since. It doesn't mean that it can't happen. It just means that the fact that we had one does not necessarily mean the we'll have another."

Today's magnitude 5-point-9 quake that hit Virginia was felt up and down the east coast including here in North Carolina.