Below is a map posted by the U.S. Geological Survey showing the epicenter of Friday's magnitude 3.6 earthquake in the Washington D.C. area.
The red dot marking the epicenter is adjacent to the major highway 270 which runs from upper left to lower right in the map.
For conspiracy enthusiasts among you, note that just a few hundred meters away you will see the U.S. Department of Energy, formerly the Atomic Energy Commission.
I know this because my first real job after college was with Fairchild Space and Electronics Company, an aerospace firm located across the street. I annotated Fairchild on the map below, although I don't know what is located there now.