Flashback to December 9, 2003: It’s a typical day at BRO headquarters. I’m laboring over some copy that’s already past deadline, when suddenly the belly of the earth begins to growl. I glance over to the desk of account executive Sara Teaster, who shoots me a bewildered, deer-in-the-headlights stare. Panning to the right, our fearless art director, Travis, has already curled up under his desk, apparently remembering the first lesson of elementary school safety drills. All the while our second story office in downtown Charlottesville is trembling even more than our jittery bookkeeper.

Fifteen seconds later, things are back to normal, and we gradually come to the conclusion that we’ve just experienced an earthquake. But aren’t we in central Virginia? Don’t these things only happen in California? It seems the Blue Ridge region is much more seismically active than some might think.

“Earthquakes aren’t very frequent here,” says Martin Chapman, director of the Virginia Tech Seismological Observatory. “But they can occur just about anywhere on Earth infrequently.”

The quake in early December, which started from an epicenter located about 30 miles southwest of Richmond, measured 4.5 on the Richter scale. Minor structural damage was reported, and light effects were felt as far away as Ohio. According to Chapman, it was the largest activity our region has scene in more than 30 years.

For the less scientifically inclined (like me), Chapman explains in layman’s terms that an earthquake is basically a release of stored-up strain energy.

“It’s the same sort of thing that happens when you stretch a rubber band,” he says. “If you stretch it, it builds up a stress inside the material. If it breaks that strain, energy is released, and most of it goes away as seismic waves.” Earthquakes are associated with the boundaries between plates in the earth’s crust. One of the most seismically active plate boundaries is the San Andreas Fault in California. Most of the Southeast is safely located on the interior of the plates; Southern Appalachia is smack dab in the middle of the North American tectonic plate. Though sesimic stresses can occur here, too, Chapman says the strain rates are a lot less than on the boundaries, so big earthquakes are less frequent. However, there are smaller fractures and fissures even on the interior part of plates that can cause earthquakes like the one we experienced in December.

“We have a lot of small faults that have been generated over the past billion years in a whole series of geologic events that were responsible for the ancestral Appalachian Mountains,” Chapman says. “All of these faults out there in the ground are little plains of weakness. When you have stresses building up, like we do, in some cases the stresses will exceed the strength of the fault and they just slide and release the elastic strain energy.”

According to information listed by the Virginia Division of Mineral Resources, the first recorded quake in Virginia occurred in 1774. Since then, 300 earthquakes have been recorded within or near the boundaries of the Commonwealth. Eighteen of them had a magnitude of 4 to 4.5 or higher on the Richter scale. The biggest event recorded was in Giles County in southwestern Virginia in 1897, which had a magnitude of 5.8.

The largest seismic event on the East Coast happened with the Charleston Earthquake of 1886, which recorded a 6.9 on the Richter. The effects of the Charleston quake were felt from Georgia to Pennsylvania.

Should we be worried? Chapman says the earthquake that happened back in December is an example of something that is going to happen again, probably within the next 100 years, but it is too hard to tell how susceptible our region is to something bigger.

“When we talk about bigger earthquakes that could potentially cause damage, we just don’t know a lot,” says Chapman. “Earthquake prediction is extremely difficult and we’re still a long way off from being able to do it reliably.”

-Jedd Ferris