New Madrid is a town in southern Missouri with a fault nearby.  It isn't
well known to the public, but seismologists know it well:
16 Dec 1811: Magnitude 8.6
23 Jan 1812: Magnitude 8.4
7 Feb 1812: Magnitude 8.7

Magnitudes are Richter Scale estimates.  For comparison the 1906 San
Franciscon quake on the San Andreas was 8.3.  So that 8.4 up there is

But not the biggest.  The Mississippi ran uphill during some of those
shocks, and foot-high waves ran through the ground like surf.  Whee!