This story was updated Friday, July 16, 2010, at 7:23 p.m.

A 3.6 magnitude earthquake today near Gaithersburg was felt throughout Montgomery, Frederick and Prince George's counties, but there are no reports of injuries or damage or of disruptions to utilities and other services.

City, county and state crews were out early this morning after the 5:04 a.m. quake inspecting bridges, water tanks and towers and dams. The quake was felt in portions of Maryland, West Virginia and Pennsylvania.

The earthquake rumbled through Montgomery County and surrounding areas this morning, according to the U.S. Geological Survey. Its epicenter was slightly north or northeast of Gaithersburg.

Asst. Chief Scott Graham with the Montgomery County Fire and Rescue Service said no injuries or damage had been reported. Further south in Prince George's County residents felt the quake but there were no actual injuries or property damage, county fire officials said.

Capt. Paul Starks, a spokesman for the Montgomery County Police Department, said police began receiving an increased number of calls following the quake. The calls were to inform police of the quake itself, not to report any damage or injuries.

Prince George's County Fire/EMS spokesman Mark Brady said county 911 dispatchers received about 2,000 calls from residents within a half-hour after the earthquake, but there were no reported injuries or damage.

"[The calls] did not require a dispatch," Brady said. "It was just people saying, ‘Hey, what's happening?'"

Mid-Atlantic faults ‘abundant'

Since January, there have been eight 3.0 magnitude or greater earthquakes and more than 50 smaller temblors in Northeastern North America, a broad swath of land described by the USGS.

Dr. John Ebel, director of the Weston Observatory in Weston, Mass., far from the quake, was woken by his pager just after the first rumbles. He got online and started to look at the wave forms and tried to track where they were coming from.

After the United States Geological Survey sent initial information about the quake's origin – culled from data collected at monitoring centers throughout the Northeast, including at Weston – Ebel started looking for historical information so he could identify a fault line. "That's what I try to do whenever there's an earthquake in this area," Ebel said. He found that "we really hadn't seen any earthquake activity before right in this exact area."

Ebel said earthquake activity in the northeast is hard to prepare for because the land is crisscrossed with faults – some of them thousands upon thousands of years old – and earthquakes here just don't line up on faults the way they do in, say, California.

"Geologists can find abundant faults in the eastern part of our country," Ebel said. "The question is not where are the faults, but where are the faults that could be active today? That is what we have not been able to figure out."

Jolted awake

In Gaithersburg, City Councilwoman Cathy C. Drzyzgula said she was awoken by the quake.

"I was pretty surprised and scared," she said. "My first thought was that a vehicle had crashed into the house."

After looking outside and seeing that her house was okay, she began to realize what had happened.

Nothing fell down or was broken, and no one was injured, she said.

Many residents reported a longer rumble followed by a final jolt. Ebel said there might have been two separate quake incidents at almost the exact same time. "We may actually be able to show, with enough analysis, that there were actually two separate earthquakes: One long earthquake, then a couple seconds later, one big, violent earthquake," he said. 

So can residents expect aftershocks, or perhaps an even larger quake? "No way of knowing," Ebel said. "Normally, there's an earthquake like this and then the Earth quiets down."

Curious callers

It was pure curiosity, not harm, that caused a marked spike in 911 calls, said Chris Voss, manager of the Montgomery County Office of Emergency Management and Homeland Security.

The high call volume was manageable this time around, but could present a problem during a more catastrophic event, he said. "If there were people that were injured and calling 911, and others are calling just to see what happened, they would be impeding the process of getting help to those that needed it the most," Voss said.

After the spike in calls, Montgomery County sent out a message through the Alert Montgomery announcement service, which sends written messages to emails, phones or other electronic devices in emergency situations. "If people want to know what's going on and are concerned, this is one of the quickest and best ways we push information out there," Voss said.

Residents can sign up for the system at http://montgomerycountymd.gov.

Service not disrupted

Representatives from Metro and MARC reported no problems with commuter trains which had just started running before the ground started shaking.

"There was no interruption to service. We have no impact that we are aware of from the earthquake this morning," said Angela Gates, a spokeswoman for Metro.

Terry Owens, a spokesman for MARC, the train service experienced no damage or delays Friday morning along the Brunswick line, which was closest to the epicenter.

Washington Suburban Sanitary Commission spokeswoman Kira Lewis also reported no issues. "At this point, I do not believe that we've had any reports of damage. It has been business as usual," she said. Lewis said the utility is usually notified by customers about small breaks in pipes or collecting water. Major damage to the water system would have been detected by a system-wide drop in water pressure, which didn't register.

Keith Brown, Frederick city's director of Public Works, said none of the 10 crews he sent out to inspect the city's infrastructure had called in any problems. They are doing visible inspections, he said, and he should know more later in the day.

Inspecting the infrastructure

State highway crews were also out early checking bridges from Frederick to Washington, D.C.

"At 8 a.m., crews began inspecting bridges, starting on I-270 in the Frederick area and heading south to 495, 95 and 29. We have not found any evidence of damage," said Dave Buck, a State Highway Administration spokesman.

Buck said the crews are not doing full inspections, which would take all day, but are concentrating on the piers and railings. They will be out most of the day, he said.

Seamus Mooney, director of emergency preparedness for the Frederick County's Office of Emergency Management, said he has crews out looking at dams in the southern part of the county.

"It was a little surprising because it's not a common occurrence," Mooney said. "The last one in the area was in 1990 and registered 2.6."

Mooney said the buildings most at risk are the older, stacked-brick buildings where minor shaking can cause some problems, but none have been reported.

Frederick Mayor Randy McClement lives in an 1899 house downtown. An early riser, McClement said he felt the shaking, and thought at first it was blasting at the quarry or a fire truck going by his house.

He said he felt a blip of an aftershock about 15 minutes after the 5:04 quake. When he realized what the rumbling was, he said he put on his mayor hat and called the Frederick Municipal Airport to see if there were any reports of damage. There were none.

‘All of a sudden I felt something'

Brunswick administrator Dave Dunn said the quake didn't do any noticeable damage to the city. "We haven't heard of any damage from the earthquake," Dunn said.

Middletown administrator Drew Bowen also said there was no reported damage from the earthquake in Middletown.

Cpl. Jennifer Bailey, spokeswoman for the Frederick County Sheriff's Office, said the county's Emergency Communications Office received multiple calls following the early morning quake, but all were inquiries, not reports of damage or injuries.

James Collins, a spokesman for the Laurel Police Department, said the station received between 25 and 30 calls from residents who did not know what had happened.

"Shortly after it happened, the phone lines lit up," he said.

No injuries or damage was reported, Collins said.

Shantay Dabney, a District Heights administrative assistant, said she felt her bed rattle at her home in Severn in Anne Arundel County and saw items on her dresser drawer shake shortly after 5 a.m.

"It was kind of crazy but I know I don't live close to trains or anything so when I sat up I said ‘This would be weird if it was an earthquake,'" Dabney said. "And it was."

Daryi Brown, 14, of District Heights, an intern for the city of District Heights said she felt the vibrations and was shocked when she later learned it was an earthquake. She said she did not think earthquakes happened in Maryland.

"I was in my bedroom and I was reading my book and all of a sudden I felt something and I thought it was just my leg twitching and then my bed vibrated a little bit," Brown said. "I didn't really know. I didn't think anything about it."

Bladensburg Code Enforcement Director Tim McNamara said town officials and residents did not receive any reports of residents feeling the earthquake.

Bowie Councilwoman Diane Polangin said she was awake at 5 a.m. watching TV when her house started to shake.

"The house started rattling, and I thought that it might be a plane but I didn't hear an engine, so I thought it might be flying really low [and might crash]," she said. "Everything was moving around for about 15 seconds. I've never experienced anything like that. I'm so glad we don't live in California."

Staff Writers Danielle E. Gaines, Katherine Heerbrandt and Tripp Laino contributed to this report.

Did you feel the earthquake? If so, we'd like to hear your story. Send an e-mail, including your phone number, to Gaithersburg/Germantown editor Comfort Dorn at cdorn@gazette.net.