[JustPiper]

Sioux Falls SD?
http://earthquake.usgs.gov/recenteqsUS/Maps/US10/37.47.-105.-95.html

[appalachian_dweller]

Yep. There are faults everywhere. A few years back in Manassas, VA there was a 4.4. Lots of folks called 911 to report some type of explosion. They had fire trucks out looking for damage until they figured it out.

Small quakes are good. They release energy preventing a larger quake. It's the faults that only move every 1,000 years or so that cause the most trouble. When those move, they REALLY move.

IIRC, there's a sizable fault running right under NYC.