Whoa - was that the ground shaking?

Last night, as Christopher was relaxing after work, sitting in front of the computer, he felt his first ever earthquake! Even though it was a pretty big one with a magnitude of 4.72 (42 miles north of San Francisco), he wasn't at all scared. The ground felt like a waterbed for about 6 or 7 seconds, and then, there was a brief aftershock after a pause. Thereafter, everything was back to normal. Though 6 seconds don't sound like a lot of time, try stumbling about while counting to 6.


Check out his first quake on the usgs links below:
http://quake.usgs.gov/recenteqs/latest.htm
http://quake.wr.usgs.gov/recenteqs/Quakes/nc40187964.htm