Wow, it was kind of hard to miss... I was sitting outside on my elevated deck, and it really shook! And it lasted quite a while, too. My dog jumped up and looked at me like it was my fault.

My neighbors are having a pool party, and didn't seem to notice anything.

Felt it in Abingdon. Lasted about 4 - 5 seconds. House shook. Was much more impressive than the little tremors we've had over the past 10 - 15 years.

WHOA!! was outside at Sherwood south of St Michaels.....walking the dogs and chatting with a neighbor Guy... We heard a HUGE long explosion, I thought a boat blew up..... And the ground was shaking side to side, things were shaking inside, we were rinning around the shore line looking for smoke!!! Trying to account for friends and family!!

I also felt the quake. I was napping on my sofa and suddenly the sofa was vibrating. Book shelves swayed as knick-knacks fell to the floor. My two dogs barked like crazy. We ran to the back door. A few minutes later it was over. Very strange sensation.

PS I live in Remington.

Felt a tremor in Glen Burnie, shook the entire house

We felt it too in OC maryland...wasnt sure whats going on at first...It was about 15-20 seconds shake.....
Any tsunami warnings?

I'm in Westminster MD and felt the tremor for about 2 mintues. Shook the whole house and made a really bad cracking noise. Scared me and woke everyone up. First thing RUN for the door frame...

Here in the Pinehurst (off N. Charles Street) neighborhood it lasted about two seconds and was enough to shake our house. A friend in Albany N.Y. also felt it.

So, when was the last time MD had an earthquake of this magnitude?

We felt the earthquake in Owings Mills too...the whole building was shaking....

Felt here in Towson (nr Loch Raven Dam). Standing outside; strongest event I ever felt (which is not saying a lot being life-long easterner). Was like the deck being hit by a helicopter!

Coolest thing was that when we came in the house fully 10 minutes later, the pendant lights hanging from the living room ceiling were still gently swinging in perfect unison. There are 4 of them hanging on 6-7' wires from an 8' track that is about 13' off the floor. Have been kicking myself that I didn't think to grab my camera & shoot a video...grrr!

How long DID it realistically last here? My "feeling" was almost a minute before I figured out what was happening, and then another minute after I had eliminated other possibilities, but I'm thinking it didn't really take that long. It's interesting the posts here range from 2 seconds to several minutes also. I'm sure science has studied this time-perception-in-unusual-scenarios thing, so I'm really curious about this.

Those of us perceiving it for longer -- were we just more aware of our brains processing the info? Would we have had more time to react (if I even knew the right way to react?) like the slo-mo feel of a car accident? Or were those who thought it was briefer actually more in tune with reality?

(I was also outside, back porch, internet off trying to get work done, when it happened. Context cues may have been different if inside or with other people in my immediate vicinity.

Charles Village. House shook quite intensely for about 30-40 seconds, though it felt like it came in two waves. Sounded like a giant was running across the roof and up and down the walls. Cats look petrified and just stayed still in crouched position. Neighbors all went out onto our porches to ask each other what was going on.

I experienced an earthquake in Guatemala that woke me from a dead sleep, so by the time I was able to figure out what was going on, it was over. And there, of course, it's expected. But in Charm City? Freaky.

Federal building in Hopkins Plaza: first it sounded like heavy equipment (say, Sherman tanks) on Lombard Street, and then the big metal bookcases started swaying and we evacuated.

Pulled up to the curb in front of my house in Parkville, and the car started shaking- I thought something really unusual was happening to the engine, which is where the motion felt like it was coming from. I turned off the radio to try to focus on the rocking and where it was coming from in the car. Sat there 5-10 seconds then pulled away from the curb slightly and it continued rocking. Then pulled into the street and it stopped rocking. Came back around & parked, thinking, I'll have to get the car checked out. Never once thought of an earthquake until my neighbor knocked on door and said "Did you feel that earthquake??"

I'm just glad there is nothing wrong with my car!!

I'm wondering if the earthquake today was predicted?

FR REPLIES: No. Although some scientists are working on it, earthquake forecasting is not yet very well developed.

I'm in Ellicott City, by the way. April, time perception is definitely variable from person to person. The quake itself lasted a couple minutes at the epicenter (if I read the graph right), and it seemed to (me) take a long time to really stop. I would say it lasted a good minute or more.

I found it interesting that my daughter felt it, working on a boat at the Inner Harbor. They were pretty confused until they got back to the pier to learn that there had been an earthquake.

Auditorium of Lake Clifton High School. Felt it in the seat and floor on my feet, feeling it deep. Then I looked up at the huge ampitheatre and the entire huge room was moving back and forth- walls, celing, stage. All were quiet, stunned I guess. Then it started again. At that point I quickly exited the building, hearing behind me people shouting "don't panic, walk in single file like a fire. I just kept going. After that it was me shaking!

Here in Sparks, we had real rumbling. This flat-roofed one-story building moved significantly. Bunch of women, grabbing their purses and heading for the parking lot. A few, with adolescents at home alone, left in a cloud of dust.

Pasadena. We've battled squirrels in the attic, so my first thought was: the varmints have called in giant commandos. I fled out the front door and onto the lawn, checking the roof. Then I felt waves in the ground, heard the antenna (yes, we still have an antenna) hitting the chimney, and knew it was an earthquake. Biggest I've felt in Maryland.

I was in the Wolman Building getting a permit. When the building shook, all of the clerks got up and ran out. When I asked about my permit, the one woman who didn't leave said "Just show the inspector your receipt. I'll mail you the permit." And who said there aren't any good civil servants?

Any tsunami warnings?

FR REPLIES: No. The earth movement was beneath dry land, not the ocean.

My spouse and I were on the fourth floor of a hospital near central Baltimore. I felt shaking while sitting in a chair backed up to a desk, thought person at desk was moving it around! It took another person coming in, asking us if it was an earthquake for it to sink in. Biggest one I've ever felt.

FR REPLIES: The only comparable quake I've felt was in the 1980s, in Los Angeles. It was an early-morning magnitude 6.0. My wife and I, our kids and my mother-in-law were on a western camping trip, but we'd camped for the night in a hotel near Disneyland. Around dawn the room began to shake, and the lights swayed. I saw later that the water in the hotel pool had sloshed over the rim. Pretty exciting, but my son slept through it.

Any info from the Virginia well that is sensitive to seismic activity?

FR REPLIES: Not yet. I'm hoping he quake didn't wreck the well's sensitivity to seismic waves from around the world. You can check it here: http://va.water.usgs.gov/earthquakes/index.htm

I was just getting up from a meeting in Columbia when I felt the first vibration. A few seconds later the floor started moving. I was close enough to look out a window and I saw the building vibrating. Not something I want to go through again. I prefer the small 3 or 4 on the richter scale that rattle the water pipes.

Frank, though I know it will be pooh-poohed by the industry giants, all the fracking going on in the Marcellus Shale might have something to do with this.

FR: The Marcellus shale formation is not near the epicenter of Tuesday's quake. Earthquakes happen.

P.S. Hilarious earthquake photo: http://bsun.md/paVWeM

The USGS has created a website showing the locations of wells that responded to the Aug. 23, 2011 earthquake. In Maryland, response was seen in Baltimore, Allegany, and Carroll Counties.