Well, we had an earthquake yesterday in Southern California. While we are well known for earthquakes here in California, there is actually seismic action going on all over the world at any given minute. Today's Social History Website is the list of historic earthquakes from the USGS, http://earthquake.usgs.gov/regional/states/historical.php. The list begins in 1568 and ends in 2008.
You can also look at a historic map of earthquakes in the US from 1750-1996 at http://earthquake.usgs.gov/regional/states/us_damage_eq.php. Check it out-you'll be surprised at how many earthquakes there are all around the United States. Maybe your ancestor even felt one.