Hi All. As most know the New Madrid Seismic Zone is a failed rift and is known as the Reelfoot Rift.

Studies show that such rifting apparently began about 600 million years ago beneath the present Mississippi River valley. Although the rift, called the Reelfoot Rift, failed to completely rupture the crust, the pulling apart of the rocks caused the formation of a zone of weakness in the Earth’s crust. As the North American plate pushes against the Pacific plate, compressional forces are probably causing stress on these weakened rocks, which is occasionally relieved when the rocks slip past each other during an earthquake.

On 06/18/2002 there was an M>5.0 quake 10 miles from Evansville, Indiana (37.99N/87.79W.) The “moment tensor solution” for this quake shows it to be a “pure strike slip” quake. Other “moment tensor solutions” for quakes along the Reelfoot Rift show everything from strike slip to strike slip with thrust faulting component to pure thrust faulting. The Evansville quake isn’t the kind of quake one would see if compressional forces were occurring in this area. This is just speculation on my part and there is no way to prove, or disprove this that I’m aware of, but there is a possibility that this particular area is going from compression (thrust faulting) to strike slip faulting to normal faulting. In other words the area is returning to a rift zone. To prove, or disprove this would take many more quakes and many thousands of years if not more. Of course there are many more ways this could end up being. It could become a new slip strike fault similar to the San Andreas Fault then again it could stay as it is. Anyway I’m sure it’s making some seismologist scratch their heads. Take Care…Don in creepy town

• Reelfoot Rift