There is another sci-fi novel that occurs to me, which had some big waves hitting the Los Angeles region. I recall it was called "Lucifer's Hammer." But I can't think of the author's name. If I remember correctly, the LA surfers come out in force to ride the big ones!
Someone! Help me here!
Question 1: "Deep Impact".
Question 2: Larry Niven and Jerry Pournelle. (I loved the tsunami-surfing bit, which ends abruptly in downtown L.A.)