It is not, but the earthquakes of 1811-12 generated from the New Madrid fault line and caused the Mississippi River to flow backwards and changed its regional course permanently in many cases (the highest Richter scale reading was either 8.3 or 8.6). In 1990, a man by the name of Iben Browning predicted a repeat of this event and it was akin to the Y2K panic. It was supposed to happen on Dec. 3rd, but alas... nothing happened. My mom did let me stay home from school that day, though. Poplar Bluff gets a lot of tremors and we have felt them throughout the Boot Heel and into the St. Louis region. Fairly common.

I will say that there is a lot of mining activity here due to the natural limestone beds and yes, there are a million cave systems. Could be man-made tremors, too.