Some of that might be tsunami. But the dead stumps and sand indicate that the coastline dropped in elevation into the ocean. By quite a bit - 10 to 20 feet iirc. Imagine what happens if you take miles of coastline and lower it 20 feet in 10 minutes!
BTW - this news is nothing new. It has been in the geology community for at least 15-20 years. And in the local papers since 2001 when we had the Nisqually eq, and lots of people woke up to the fact of what a large eq can do.
And it WILL happen. Who knows when, but when it does, it will happen in an instant. Be prepared.
Yeah the coast did drop but this is up the river several miles. There are beaches where sand erosion exposes tree stumps that were well above the water line at one time. The upper edge of the subduction zone sank when the earthquake released the tension on the upper side of the fault. The same thing happened at points in the Great Alaska Earthquake. Land settling is common but unpredictable at this point. If we could map and quantify the stress on different sections of the fault, it would help preparations greatly.