WASHINGTON — A minor earthquake shook residents awake in and around the nation's capital early today, rattling windows but apparently causing no serious damage.

And while Californians might scoff at the 3.6 magnitude quake, Susan Potter, a geophysicist at the U.S. Geological Survey, said it was the strongest to hit within 30 miles of D.C. since they began keeping records.

The quake hit at 5:04 a.m. and was centered in the Rockville, Md., area said Randy Baldwin, a geophysicist with Geological Survey's National Earthquake Information Center. Baldwin said aftershocks could occur during the next couple days, but none had yet been reported. He said the aftershocks are generally of a smaller magnitude than the initial earthquake.

Police in Washington and in nearby Montgomery County, Md., said there were no immediate reports of injuries or damage.

On the U.S. Geological Survey's website, people as far away as Pennsylvania and West Virginia reported feeling the quake.

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 today's quake and a 2.3-magnitude quake in 1996 that was within 15 miles, Baldwin said.

"The thing that makes this earthquake distinctive is that is was felt widely over the region," he said.