Don, I though that each increase of 1 on the Magnitude scale meant 33 times the energy. So, the difference in energy between a 5 and 8 should be 33*33*33=35,937, not 1,185,921. So, with John's comment that the energy in a nuclear explosion is higher than its Ms, it starts to look like the nuclear explosions might equal a M8. But, that does not mean that they can trigger anything at great distance.....

Although I think you realize this, if M8s are random and there is 1 on average every 1 or 2 years, the statistics of there not being one in a 100 year period would be vanishingly small (but I don't know how to do those statistics, simple though it may be, and don't feel like looking it up...). Chris