Thank you for this excellent link. I know I will study it in detail. Actually while 3 of the quakes were extremely strong, there were dozens of others during about a 6 month period that would have been noteworthy in most other cases. There was also a major quake in Venezuela in the spring of 2012 that killed perhaps 20,000 people. St. Vincent in the Caribbean also had a major volcanic eruption in 2012. Obviously the whole Caribbean Plate was influencing neighboring areas.
Many more links here:
http://hsv.com/genlintr/newmadrd/index.htm
Yes, 3 truly major shocks, another almost as large, dozens that would otherwise be considered very serious quakes (especially given the local geology), and hundreds of smaller ones. From USGS:
“In total, Otto Nuttli reported more than 200 moderate to large aftershocks in the New Madrid region between December 16, 1811, and March 15, 1812: ten of these were greater than about 6.0; about one hundred were between M5.0 and 5.9; and eighty-nine were in the magnitude 4 range. Nuttli also noted that about eighteen hundred earthquakes of about M3.0 to 4.0 during the same period.”
http://earthquake.usgs.gov/earthquakes/states/events/1811-1812.php
IIRC, one account spoke of continuous ground motion for a period of days.