New Madrid? None of the geowhizical geniuses claim to have a theory about what activates the NM. But I think shakes like this are precursors. In my view there is a lifting force from the Rockies, the Rockies being formed by collision, that translates all across the great plain, the Great Plain being a huge slab of sediment. The break is in the Mississippi River valley which is the natural low spot, and the NM is the area where lift pressure is the Max——think prybar with 1,000 mile long handle. Naturally I could be full of stuff but nothing that has happened in the half century that I’ve been watching runs counter to the above spiel.
You are not full of stuff, I enjoy every post of yours I come upon. Very satisfying, your are :)