I M4.4 now. When you look at the USGS historical seismicity map, there is quite a cluster in this area. But, I don't know whether this cluster on the map is older quakes or from this swarm (maybe both?). I speculate that fluids in crust have something to do with this (well, of course they have "something" to do with it, but I mean more directly). I was curious where the quakes in Guy were relative to Hot Springs. They are not close, but they are in a NE-SW line.

My advisor at Georgia Tech, L. Tim Long, had a paper on quakes like the New Madrid ones where they are started by fluids in the lower crust that eventually weaken the crust, and the high stresses that are in eastern/central USA crust trigger increasingly large quakes, and then it is all over, forever (after thousands of years, I suppose). He though that the eastern Tennessee seismic zone might fit that description.

I think this was a speculative hypothesis, but it makes some sense.

The recent quakes in Guy may not fit theat description because they are relatively shallow.
Chris