[hanamizu]

Besides the fact that the New Madrid quakes can be quite large and can be felt very far away, consider, older St. Louis is built out of brick. If a big one hits here, there will be a lot of damage.

[cuban leaf]

I checked the damage map from the last serious Madrid quake. The edge of the area on a map indicated it stopped about 15 miles from where I live. :)

[Publius]

A megaquake on the New Madrid could destroy all the locks on the Illinois Canal. That would permit the upper three Great Lakes to drain via Lake Michigan, the Chicago River, the Illinois Canal and the Illinois River into the Mississippi River. That would turn the Mississippi into something 20 miles wide from Grafton all the way to the Gulf. St. Louis would end up underwater.