text:  is like a finger pointing down to New Madrid, Missouri. And there have been a number of seven-magnitude quakes along that major suture. They call it a geo-suture. And it's a zone of weakness, and unusual rock types develop along it. And there have been some very destructive quakes going back into colonial times. And, of course, you mentioned Pennsylvania. You know, they had a couple of 4.6s just about two years ago near Harrisburg. Surprised everybody. The largest quake in the history of Pennsylvania.