Wow, I saw this one earlier, Ernest, then my computer crashed. Thanks for posting this story!
There was a 4.2 near mammoth today also I think.
Well it a long way from Mt. Diablo.
I lived at the base of Mt. Diable in my last home before coming to the Oregon Coast 17yrs ago and grew up with it in view.
I think it was the Hayward Fault that ran through that area.
Nt. Diablo has an interesting history of how it was named and the indians who lived there long ago. We use to love going up there as kids and thought every hole carved out was an indian bed. LOL