So, Arkansas isn't really moving into a New-New Madrid as fast as I thought. Do you think they are really stopping injection when they get earthquakes? That would really throw me off! :) Human rationality aside, I think all these clusters have been injection zones, and they were stopped by aliens.
Now we got a new spot, but it doesn't fit into any pattern. I guess somebody just threw a hole down there, but I can't see it being a high-flow spot. Anyway, this whole US injection scene is becoming boring, I think there are some nefarious black helicopters behind it.