The Roanoke Valley was shaken early Saturday by a magnitude 3 earthquake that rattled buildings from Vinton to Salem and prompted people to flood emergency dispatch offices with dozens of calls. There were no reports of injuries or property damage.

The epicenter of the quake, which struck at 4:08 a.m., was in the Cave Spring area near Garst Mill Road, the U.S. Geological Survey reported. According to researchers, similar incidents are recorded about once a year in Virginia, but most are hardly noticed because they typically happen in sparsely populated areas.

"These earthquakes are fairly ordinary," said Martin Chapman, a research assistant professor of geophysics at Virginia Tech. "There's nothing remarkable about it, other than the center being in a populated area."

Many people who were interviewed or who called emergency dispatch offices said they did not immediately suspect that a quake had struck the region. Many people said they initially believed an explosion or an object striking their residence had caused it to shake.

The USGS initially reported the quake registered at 2.6, and throughout the day upgraded it to 2.8 and then 3.

John Bellini, an USGS geophysicist, confirmed quakes are not "common everyday occurrences" in Virginia, though they might be on the West Coast.

He said that faults occasionally move slightly and cause minor quakes in the state, most of the time not causing any injuries or damage.

The fault lines with the most history of producing earthquakes in the state are in Giles County and west of Richmond along the James River in rural Goochland County, Chapman said.

On December 9, 2003, the ground shook for about 10 seconds during two earthquakes measuring 4.5 in Goochland County, he said. In 1897, railroads were blocked by fallen rocks and springs dried up in Giles County after an earthquake recorded at 5.8.

Chapman said that aftershocks, or post-earthquake tremors, may happen until Monday.

"We're going to keep an eye on it to see if we see other earthquakes coming from that area, but it's pretty much an ordinary little thing," Chapman said. "Things like this are just a little friendly reminder that earthquakes are a hazard even in the state of Virginia."

Throughout the Roanoke Valley, people said they initially believed a tree or a vehicle had struck their home, or that a nearby explosion caused their home and windows to shake.

In the Cave Spring area, the epicenter of the quake, people carried on with what seemed like a regular Saturday: People checked their mail, moved boxes in and out of houses, and cooked burgers on grills.

Richard Golladay, who lives with his wife and daughter two blocks from Garst Mill Road, said that he woke up and felt his bed was off-level and his house was shaking.

He said that after the tremor, he went outside to check if an object had struck his house, and saw his neighbors were doing the same.

"I was somewhat relieved when I saw my neighbors were also up," he said. "It was such a foreign and alien experience that I experienced curiosity more than anything else."