Depending on the source, there were 3 or 4 major New Madrid quakes, with 3 being near or at magnitude 8.0, and, it would seem, the last big one possibly being the greatest. There were also thousands of other “aftershocks”, and I believe I read somewhere that the ground was in motion nearly continually for about a month. The geology in this region also helps transmit the waves efficiently — check out the map showing damage areas in the excellent article on Wikipedia:
http://en.wikipedia.org/wiki/New_Madrid_Earthquake
(Lots more links there too...)
Thank you Paul. That was a great resource. I appreciate it.
The Mississippi River changed course in at least one place due to those earthquakes or most likely because of the largest, and I have read that it actually ran backwards for a short period in some places. Yikes.
What concerns me these days is that there is now massive population in the area. And building codes back there are nothing like California’s. At least that’s my perception.
Take care.