WASHINGTON -- Earthquakes are so rare in the Washington area that even a geology student wasn't quite sure what was going on when a minor one hit early Friday. Was it a truck passing by? A low-flying plane?
Gerasimos Michalitsianos, who will be a senior at the University of Maryland, College Park, was sitting on his couch looking at e-mails when the 3.6-magnitude temblor occurred.
"I didn't actually know that I was in an earthquake," said Michalitsianos, who is studying postseismic relaxation, how the ground changes following major earthquakes.
Michalitsianos said he only found out he'd been through an earthquake when he looked online.
"It was a rare treat to see an earthquake occur here on the East Coast and to actually feel it," he said.
Washington area residents are used to politicians being the region's movers and shakers, so it was a surprise when the earth below shook. The earthquake rattled windows and jostled dishes but apparently caused no serious damage. President Barack Obama told reporters he didn't feel it.
Though Californians who have earthquakes of this size almost weekly may scoff, it was the strongest to hit within 30 miles of D.C. since officials began keeping records in 1974.
The quake happened at 5:04 a.m. and was centered in the Rockville, Md., area, said Randy Baldwin, a geophysicist with U.S. Geological Survey's National Earthquake Information Center. By noon, more than 15,000 people had logged on to the U.S. Geological Survey's website to report feeling it, some from as far away as Pennsylvania and West Virginia. The website said earthquakes east of the Rocky Mountains can be felt over an area as much as 10 times larger than a similar magnitude earthquake on the West Coast.
Police in Washington and nearby Montgomery County, Md., said they received many calls from residents Friday morning, but there were no immediate reports of injuries or damage. Water, gas and electric utilities reported no problems to the District of Columbia Department of Homeland Security, which said streets were clear and the subway wasn't affected. Crews did go out to inspect bridges, however, to check for damage. None had been found as of midday.
Residents, meanwhile, spent the day asking each other "Did you feel it?"
Matthew Castelli, 40, of Fredericksburg, Va., said he didn't.
"I understand in this area for a lot of people it's 'holy cow!'" he said. "I think people tend to forget that we're near a fault line around here."
The Washington area has had small, infrequent earthquakes over the years, including a 2.5-magnitude quake in 1997 that was within 25 to 30 miles of Friday's and a 2.3-magnitude quake in 1996 that was within 15 miles.
One earthquake larger than a magnitude 5 was recorded in the area in 1897, and it's possible one might occur in the future, but it would be an extremely rare event, said USGS geophysicist John Bellini. Earthquakes in the area occur on fault lines called intraplate faults because, unlike California's San Andreas fault and others, they are not on boundary lines between the six or so large plates that make up the Earth's crust.
Debby Taylor Busse said she was watching television in the basement of her home in Vienna, Va., when she felt the quake.
"I didn't know what it was," Busse said. "I have never been in an earthquake before. It felt like an airplane going overhead or thunder, but it wasn't coming from above."
Busse said it lasted just a few seconds and compared it to a strong thunder strike -- enough to rattle the house, but not enough to knock anything over.
Tafelila Pilgrim, 78, said the shaking was strong enough to knock a plastic glass of water over in her home, but nothing else was amiss, though the quake shook her.
"I start screaming," she said. "I was afraid."
Washington resident Denver Turner said he too was awake to feel the quake. He'd been answering e-mails when he felt the carpet begin to vibrate beneath his feet.
"I didn't know DC got earthquakes, really," Turner said. "Definitely my first experience and not something I'd want to go through on a greater scale."
Associated Press writers Matt Small, Kathleen Miller and Nafeesa Syeed contributed to this report.