This is an interesting earthquake article. I'm still chewing over the implications. Are earthquakes started in 'soft rocks' better than the 'hard rock' variety? Is it just a matter of depth? The problem is that 'soft rock' implies lower stress drop, and for a given magnitude, it means the displacement has to be greater. This is not good.
Yet, it didn't wake up the poor schnooks that were camping right on top of it. They were probably camping on 'hard rock', which is good for earthquakes. Doesn't sound like the earthquake ruptured right beside them, or they would have had trouble finding the latrine in the morning!
So, this hard vs. soft thing has me very confused....