Well, on the east coast of the US, a 6.0 earhtquake could be really bad news, as almost no buildings are retrofitted to deal with earthquakes here. Whereas, in California, a 6.0 is not a big deal at all, because the buildings are built with earthquakes in mind.
Earthquakes in the western US are usually localized, not felt more than a few hundred miles away, because of the crust structure of the Earth is alot more dense (lots of mountains), and the fault lines are not all connected. However, in the East, alot of the fault lines are connected and run along the Atlantic shelf plate, so when there is an earthquake, the seismic waves travel further.
Where I live in Pennsylvania, I'm about a mile from the most active fault line in the state, and we usually get small tremors (3-4 richter scale) that sound and feel more like dynamite going off underground, usually every few weeks. This one was different though, it wasn't a loud and sudden bang, it was a drawn out rumble that shook for 15-20 seconds.
Regards
Friction