East Coast quakes are felt farther than West Coast ones

The reason? The rocky underground east of the Rocky Mountains is generally hundreds of millions of years older than the subterranean formations east of that range. Being older means that those rocks are harder and denser, and the older fault lines have had more time to heal.

All of that means that seismic waves travel much more easily across the eastern U.S. The reverse is the case in the West, where the much younger faults absorb more of the seismic wave energy, which, as a result, doesn’t spread as efficiently as it does in the East.

I had no idea.