There was a M4.5 on the northern part of the Alabama-Georgia border. Looking at the past seismicity and hazard maps on the USGS page, it looks like this is along trend with an eastern Tennessee seismic zone. But, M4.5 is large for this area. L. Tim Long of Georgia Tech had an interesting idea concerning this zone over 15 years ago-I think it was published-that fluids in the lower crust set off area of seismicity in intraplate areas, that this eventually leads to large earthquakes, and then the area quiets down again. You have to take into account, though, eveidence that the New Madrid zone and Charleston (town?) S Carolina have had several large earthquakes before the historical ones. But, you also have to explain how rock layers 10s of millions of years old are only offset a little bit (10s of m?) by the New Madrid area faults....Chris