Well, I was right, it WAS an earthquake, can you believe it? It was 3.6 magnitude and the largest to hit our area since 1978. Here is the quick online article from the Post:
Mild earthquake felt across region
A 3.6 magnitude earthquake rattled the Washington area early Friday, with thousands of residents reporting that they felt the ground shake as they slept or were waking. The U.S. Geological Survey said the quake was centered in Montgomery County and struck at 5:04 a.m.
The epicenter was in the Germantown-Gaithersburg area near I-270 and Route 119 (39.145°N, 77.222°W), USGS reported in a preliminary finding. Its depth was 3.1 miles.
"The whole house shook," said Carroll Ripley, of Germantown. "I thought maybe there was an explosion or a plane flew over the house or something."
"I went straight outside to do a perimeter check -- in my underwear," she said.
Authorities in the District and Montgomery and Arlington counties said there were no early reports of damage. Still, many residents were dialing 911 to report the rumbling.
“We are getting flooded with calls,” a Montgomery County police spokesperson said.
No traffic or transit delays were reported by local agencies, and the quake seemed unlikely to have any effect on the morning rush. Buses and trains were running on time, officials said.
Amy Vaughan, a geophysicist with the USGS, said the quake was the largest recorded within about 45 miles of Germantown since a database was created to track such activity in 1974. The largest earthquake before Friday morning's was a 2.7 tremor in 1993, Vaughan said. There was a 2.6 magnitude tremor in 1990 and quakes measuring 2.5 in 1997, 1993 and 1974.
"It’s not something that’s completely out of the ordinary," Vaughan said.
At the same time, quakes measuring above 3 are extremely rare in this area. Vaughan said the number of people reporting the quake to the USGS illustrated how unusual it seemed to residents of the mid-Atlantic states.
Within about two hours of the quake, more than 6,700 people had reported the quake on the agency's Web site. Most were from the District, Maryland, Virginia and Delaware but reports came from far away as New York and Georgia.
Many found it thrilling.
"It felt like the earth was churning," said Linda Wheeler, of Monrovia, Md. "I knew it was an earthquake right away because it was unlike anything I've ever experienced. It was actually kinda cool."
David Hayes, of Boyds, was getting dressed when he said he heard a loud rumbling. “I opened my front door and yelled 'earthquake' toward my neighbor, great way to start the day!” he said.
Geologists note that earthquakes can occur anytime and anywhere. They are a natural phenomenon resulting from the shifting movements of continental plates under the Earth's surface. "There are faults from when continents were moving and forming and shifting," Vaughan said. "These faults just naturally exist and over time they build up pressure."
When the pressure is released at a high enough intensity, an earthquake results.
The earliest recorded earthquake in Maryland occurred in Annapolis on April 24, 1758 and lasted a full 30 seconds, according to a history posted on the USGS Web site.
There have been other tremors reported periodically in the region through the years. None caused any significant damage, according to the Web site.
Dean Miletich, of Frederick, said he was taking out the trash when the quake hit.
“When I came back into the garage, everything on the shelves was shaking,” he said. “It sounded like a deep rumble. When I came back inside, my wife had woken up and asked me, 'What did you do?'”
Web site: U.S. Geological Survey