Thanks, Brian -

That certainly puts things in perspective. Excellent graphic and article.

At the iris.edu link discussion, it's not clear why the rock in subduction zones is "stronger" than the rock in California (presumably meaning the rock along California's major fault zones). I know the rock in California is heavily fractured, compared to the rest of the U.S.'s rock, but I would figure the same is true of the rock in subduction zones in the overriding plate, and the subducting slab is at least somewhat ductile, no?

Mike Williams