I had a discussion with a colleague today, about the likelihood of a major earthquake in California

[SheilaT]

10. Where in California?

Which fault or fault system are you anticipating failing or moving, resulting in "the big one"?

I know that at various times over the years I've read predictions of earthquakes, always given in a percentage over time. Such as a 40% likelihood of a magnitude 6 within the next thirty years.

My understanding of earthquakes is that the kind of fault, exactly how it moves, and when the last time it moved significantly all come into play.

For those who are interested, John Nance wrote the best book I've ever read about earthquakes, titled On Shaky Ground. It came out in 1988. It devotes something like five chapters to the Good Friday Quake in Alaska in 1964. That was basically the event that confirmed the theory of plate tectonics, and Nance explains all that. He also writes about the New Madrid quakes of 1811/1812, and when I read that book, it was the first I'd ever heard of those quakes. The book is no longer in print, but is readily and inexpensively available on the internet. I cannot recommend it too highly.