Question 1: "Deep Impact".
Question 2: Larry Niven and Jerry Pournelle. (I loved the tsunami-surfing bit, which ends abruptly in downtown L.A.)
I am glad somebody has a memory for these things. When you listed Niven, I said, "That's the one!"
I was working on an environmental impact statement last year, in which I had to discuss geologic hazards in the Santa Barbara Channel area. I read a couple of papers on the Maui Island mega-slides, and attended a conference in Los Angeles where these types "mass wasting" were discussed. One paleontologist talked about finding misplaced fossils in wave deposits up on the Palos Verdes Peninsula and concluded they could be sourced by mega-tsunamis.