Yep, that was an earthquake, 5.8 in Virginia, felt in Cambridge

[darxus]

http://earthquake.usgs.gov/earthquakes/recenteqsus/Quakes/at00lqe6x3.php

Comments

[darxus.livejournal.com]

I probably wouldn't have noticed it if I hadn't just seen somebody on IRC in another state say "Huh. The whole building just shook." It was a slight wobble. A coworker walking by was confident it wasn't an earthquake.