A 3.6-magnitude earthquake with a center of Gaithersburg was reported around 5 a.m. Friday, and felt by as many as 3 million people in the Mid-Atlantic region, according to the United States Geological Survey.

The earthquake was reported across the Baltimore area as well as in Virginia, Pennsylvania and Delaware. People in Columbia, Owings Mills, Carroll County and Odenton reported feeling the quake this morning, describing the movement as enough to rattle household items.

Odenton resident Paul Muirhead said the temblor woke him up around 5:05 a.m. “I was startled from my sleep as if being shaken,” he wrote in an e-mail. “Though there was hardly any light by which to see, I could hear items of mine — large and small — rattling on glass shelves.”Jessica Sigala, a geophysicist with the USGS’s National Earthquake Information Center in Golden, Colo., said there have been no reports of significant damage or injuries.

The earthquake marked the second time within a month that Marylanders have felt the effects of tremors. On June 23, a 5.0-magnitude quake with an epicenter near Ottawa sent shockwaves along the East Coast.

Sigala said back-to-back earthquakes in this area are unusual, particularly because the Mid-Atlantic states do not fall along a fault line like California. “We do have them [in the Mid-Atlantic], it’s just not very often,” Sigala said.

USGS officials estimate about 12,000 people experienced moderate shaking this morning, and about 300,000 felt light shaking. Millions of others felt at least a degree of shaking, USGS officials said.

Self-reporters in Gaithersburg and Jessup described the quake on the government agency’s website as having a Modified Mercali Intensity as high as 4. An MMI of 4 is the equivalent to the vibration of heavy trucks passing, and can cause pictures to swing and household objects rattle.

Alvin Borenstein of Randallstown said the quake woke up his entire household.

“All of a sudden, we felt the house shake,” he said. “It woke my granddaughter up, it woke my son up, and it woke me and my wife up. The house shook. We didn’t know what it was.”

Of his 60 years in Randallstown, he said he’s never had an experience like that one.

“You’re looking up at the ceiling and your house is shaking,” Borenstein said. “It was terrible. We were really really scared.”