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Earthquake hazard map for the United States (credit: USGS)

Just before 2 p.m. this afternoon, my office began to shake. At first I thought it was just another train passing by but then the shaking got stronger. Earthquake! I dived under my desk while other people ran for the stairs. The USGS quickly reported that a magnitude 5.9 5.8 quake had struck in Mineral, Virginia, about 75 miles southwest of where I sat in Washington, D.C. People reported shaking as far away as Cleveland, Toronto, Chicago and South Carolina.

When we think about earthquakes in the United States, California comes to mind. Maybe Oregon or Washington or Alaska, which also sit on the Pacific Ring of Fire, or Hawaii, with its volcanic action. But those aren’t the only places where earthquakes have occurred in the United States, as you can see from this hazard map. I was actually researching this very topic as the earthquake started; Colorado, another site not known for quakes, experienced a 5.3 magnitude earthquake this morning and I had been wondering where else might be next.

The upper Midwest is seismologically pretty safe, according to the USGS, but there’s that big red and fuchsia spot in the center, where five states meet. That’s the New Madrid Seismic Zone, and four of the largest U.S. earthquakes ever (in 1699, 1811 and two in 1812) were centered there. Scientists aren’t quite sure if another big one could happen there again, but the USGS erred on the safe side in a 2009 report and remained concerned about a destructive quake.

Another fuchsia area in an unlikely spot is in South Carolina. Back in 1886, a magnitude 7.3 quake shook Charleston, killing more than 100 people. It was the largest and most destructive earthquake east of the Mississippi. The area’s fault zone has been active for thousands of years and is likely to remain so. And if a similar earthquake struck today, one simulation estimated that 900 people would be killed and the quake would cause $200 billion in damage.

Out West, Colorado gets earthquakes rarely, but Montana, Idaho, Wyoming and Utah are more active. Montana was the site of one of the country’s most intense quakes, in 1959, when a magnitude 7.3 earthquake shook Yellowstone. And Nevada, too, isn’t quake-free.

New Englanders feel earthquakes once in a while, though they’re often centered farther north in Quebec, Canada. But Boston experienced a bad earthquake back in 1755, and New York City in 1884.

And what about Washington, D.C.? Well, as you can see from the map, the hazard isn’t zero, and it’s even higher in Virginia, where today’s quake happened. The ground could shake again. But next time, I probably won’t mistake it for a train.

(Oh, and all my colleagues who evacuated the building in fear? Well, that wasn’t the best strategy, as FEMA explains. If you’re inside, you should drop to the ground, take cover under something like a desk and hang on until the shaking stops. Then you can take the stairs, not the elevator, if you’re going outside.)

What would you do in an earthquake? (Credit: xkcd)