I'm in Frederick, MD & was at work( a local craft brewery) I happened to be cleaning some paint brushes & rollers in a floor mounted mop sink, so I was on my knees on the concrete slab the building sits on. It was really odd to feel everthing moving like that- kind of came in two separate waves. The building kind of rumbled also. We all realized what had happened fairly quickly, then got back to work. No apparent damage there or at home.