Earthquake

The U.S. Geological Survey reported a 3.6 magnitude earthquake centered in Montgomery County at 5:04 a.m. Friday. The epicenter was in Gaithersburg near I-270 and Route 124 (39.145 degrees N, 77.222 degrees W), USGS reported in a preliminary finding. Its depth was 3.1 miles.

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.

Mike Blanpied, a geologist with the U.S. Geological Survey, was online Friday, July 16, at 11 a.m. ET to discuss the earthquake.

Mike Blanpied: Good morning. Lots of people in the DC metro area were awoken (or startled, if already awake) by this morning's M3.6 earthquake, just after 5 am. I'll answer your questions about the earthquake, the history of earthquakes in the area, and any other questions you may have about earthquakes and earthquake hazards, over the next hour. I appreciate your interest.

Mike Blanpied: For additional information about this and other earthquake topics, please see our web site http://earthquake.usgs.gov.

While there, I encourage you to fill out our "Did you feel it?" form about the quake. 12,000 people have already submitted their observations, helping to build a map, color-coded by zip code, showing the intensity of shaking in the area.