I was at work in Waltham, on the 3rd floor, and it felt like a cross between a pop, thump, and bang. It was abrupt, like somebody had dropped something heavy or a cannon had gone off (without the long-lasting echo). I've felt longer quakes in Japan before and this was nothing like those, so I didn't recognize it for what it was at first.

Anecdote: I'd gone to a talk at the Weston Observatory last year about recording the audio (the impact of shockwaves with the air) of quakes, and they had a recording of a rather dull meeting in some city that was interrupted by a similar quake, which made the guy leading said meeting jump and swear really loudly. ;)

So exciting! Our planet is incredible. Earthquakes really can happen everywhere--not just at obvious plate boundaries or major fault lines.