The U.S. Geological Survey says it happened at exactly 5:04:49 a.m. about 3 miles under the earth's surface.
Officials warn there could be aftershocks in the coming days.
There were no reports of injuries or damage, but transportation crews are inspecting bridges in Maryland and D.C.
Maryland State Highway Administration spokesman David Buck says no damage had been found as of Friday morning.
DDOT crews are inspecting some of the older bridges, and are compiling a list of places to conduct more thorough evaluations, DDOT spokesperson Karyn LeBlanc says.
There were no problems reported by regional water, gas and electric utilities.
On Friday morning, D.C. Fire and EMS tweeted they were looking into whether the quake caused a crack in the roadway at 7th Street and Dahlia Street in Northwest. They later determined the quake didn't cause the damage.
Right after it happened, calls from all around Maryland, Northern Virginia and as far away as West Virginia started lighting up the WTOP newsroom phone lines.
"It was centered in the Germantown-Gaithersburg area," Randy Baldwin, a physicist with the U.S. Geological Survey's Earthquake Information Center, tells WTOP.
By mid-morning, more than 13,000 people had logged on to the U.S. Geological Survey's website to report feeling the quake, 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.
The earthquake woke WTOP listener Christy in her four-bedroom home in Bethesda.
"I was terrified. Then it was a huge jolt and my bed actually went forward from the wall," Christy told WTOP.
The USGS received 6,500 reports about this quake. While minor, this quake was out of the norm for the region.
Baldwin say the area's last earthquake was 2.0 in 2008. The region also had a 2.7 quake in 1993.
Barbara L. Thanos writes on WTOP's Facebook page: "Here's my experience. Sitting at my desk at work, by myself, and all of a sudden the computer, calculators, phones etc, starting moving, building rumbling etc. I work in Gaithersburg! Thought the building was coming down. I've worked there 26 years and never felt anything like that! I ran downstairs and out of the building to see if something hit it. Scary. Husband called and said, 'Gaithersburg just got hit with an earthquake!'"
Dave Garcia of Gaithersburg called WTOP.
"I was pretty scared," Garcia said. "I got rattled out of bed. I thought it might be a transformer, but it shook the whole building."
"I live less than a mile from the epicenter. It was crazy," e-mails Mike in Germantown. "It was really foggy and suddenly there was a loud rumble. Then all the furniture in my room began to shake and rattle and soon, the entire house started shaking. It lasted around 10 seconds and it was STRONG. Probably stronger here since I am so close to the epicenter."
"It woke me up," WTOP listener Amy Zimmerman tells WTOP. "My bed started to shake. Things fell off the shelf."
Some listeners say the earthquake felt like an underground blasting or a truck hitting a building.
"We felt the earthquake here in Columbia with walls vibrating," Darlene Brown wrote in a text message to WTOP.
On WTOP's Facebook page, Jill Lasheski of Germantown writes that she quickly woke up her husband.
"I grabbed him and said Earthquake! We are use to trains going right by our house, but this felt different- really shook our house! But did anyone else feel an after shock about 10 minutes later?? It felt the same but weaker and shorter."
D.C. emergency services says there are no reports of any damage. No injuries have been reported. The utilities reported no problems. Metro also reported no problems.
Amy Vaughn with USGS says there is a world of difference between a California earthquake and an earthquake in Maryland.
"In California, a 3.6 is almost laughable, whereas out here it's huge news," Vaughn tells WTOP. "This can be felt in a larger area, like 10 times larger an area. And, that's based on geology."
Vaughn says because of the area's sedimentary mountain ranges energy spreads farther.
"When something shakes, it goes everywhere," says Jessica Sigala, a geophysicist with USGS, about earthquakes on the East Coast.
Sigala tells Federal News Radio the bedrock is different in the eastern U.S.
"I have heard from some people that they have felt aftershocks," Sigala says.
Preliminary reports from USGS said the earthquake was a 3.7.
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