Source: Byram 2007.
Every few centuries, on average, the Northwest Coast gets shocked by a massive mega-thrust earthquake, on the order of 8 to 9 on the Richter scale. On occasion, these produce a devastating tsunami wave. It wouldn’t be surprising then if such disruptive events featured in aboriginal oral histories and also in the archaeological record itself. There is a growing body of research on this topic which I am not planning on reviewing at this time, but a nicely focused starting point is a series of papers in the Oregon Historical Quarterly, available online.
Northwest Coast Archaeology 