"If Big Quake Hits off Coast, Tsunami Could be Gigantic (Washington, Oregon, California)"
A 20 foot wave would not be "Gigantic". I saw a Discover or History program earlier this year that talked about the effects of a huge landslide off of an island off the coast of Africa -- this would result in a 300 FOOT TSUNAMI hitting the East Coast of the US.
Now THAT would be GIGANTIC.
There was a 200 foot Tsunami in some Alaska inlet and there were witnesses. A small fishing boat went for a ride.
A landslide (actually a portion of a mountain broke off) into the head of the inlet created a 200 foot wave. And it wasn't the first time it's happened.
Discovery Channel had a program about it.