Of course in his plot, exactly that happened. The tsunami was caused and petered out long before it reached Malibu.
He didn't mention the extensive damage it would have caused closer to home, though, except on the island itself. The conclusion we intuitively reached was that there was little but water between the island and the US.
I thought the way it was written, from the point of view of a committed environmentalist who realized all his ideas were wrong, was superbly effective. And I thought the character of Morton was cool.
In the story, the tsunami was only partially generated due to the heros interfering with the machinery. There was a very strong implication that if it had functioned as intended the tsunami would have indeed devastated CA.
Which is just idiotic, IMHO. Effects on Australia, New Zealand, all the Polynesian Islands, Hawaii, probably Japan, etc. would by definition have been much greater than on CA. Yet the damage to CA was supposed to be the enviro-terrorists greatest talking point.
Poorly written book, IMO.