From December 1811 to February 1812, three great earthquakes struck the Mississippi Valley region, near New Madrid, Mo.  The larges quakes in the series occurred as follows:

           

 

M8.6  (12-16-1811)

 

M8.4 (1-23-1812)

 

M8.7 (2-7-1812)

 

These triggered "violent" shaking intensities of XII on the Modified Mercali intensity scale.  The shocks were felt from Canada to New Orleans and as far away as Boston (where church bells pealed).  Buildings within the region were destroyed and chimneys were knocked down as far away as Cincinnati and St. Louis. 

 

The Mississippi River changed its course.  Trees were snapped off at their trunks, and landslides swept down steeper slopes.  Considerable areas were uplifted while others subsided, filling with water and creating expansive lakes. 

 

Although these powerful earthquakes were capable of significant surface fault ruptures, no traces have been discovered. 

 

Ongoing research indicates the stresses that produced these events still exist today.  People in the region should be prepared, as devastation would be far greater now that the population is larger and infrastructure more extensive.