Do not get to comfy one of the largest earthquakes was in Missouri in the early 1800 they estimated it at a 8.5.
http://www.dnr.mo.gov/geology/geosrv/gdam/HistoryMOeqs.htm
Although not recorded by modern instruments, a sequence of earthquakes that occurred near New Madrid in 1811-1812 included three of the most intense ever to occur on this continent. The New Madrid quakes were followed by aftershocks that continued for more than two years. More than 2,000 shocks were felt at least 180 miles away from their centers.