Randy neighbors or earthquake?

I forgot to post this in my last entry.

Last night I woke up to some pretty heavy shaking near my head. My first thought was "omg, my neighbors are going at it at 4 in the morning!" And it's really loud too. So loud, that it's practically banging against my side of the wall. It went on for another 30 seconds and then it stopped. I couldn't tell but I thought I would have to move to another apartment if I had such randy neighbors. After waking up though, I wonder if that was my first earthquake experience or just really active neighbors...I'll have to confirm later today.