Actually, about 2 million years ago a section of one of the Hawaiian islands did fall off and cause a huge tidal wave to hit the shores of southern California. No humans were there to see it, not even a primate. Probably alot of mammoths got drowned in that one.
Slow erosion is the main form of wearing down of the volcanic islands there, but some big pieces have slide into the ocean from time to time. This causes tidal waves of hundreds of feet high if you are on the island or adjacent islands. By the time it gets to southern California, it’s attenuated a bit.
