My post was stupid.
It was late and I was a bit distracted by dealing with a mine owner who doesn't know what the hell they are talking about and was trying to trick me into endorsing their stupidity. Long story, that, dating back over 19 years.
Anyway, here a link with a better description:
http://cosmiclog.msnbc.msn.com/_news/2011/08/23/7451929-small-quake-has-big-reach
However, this can also work the other way 'round. Unconsolidated sediment will amplify shaking from a quake, so in a place Like San Francisco, a house on Knob hill is safer than a house in the Marina.