Could A Tsunami Flatten PDX?

So I might have a little crush on Willamette Week's Dr. Know.

Sure, according to the illustration he might be a little rough around the edges...but he's super smart and seems to know a lot about disasters, which makes him a man after my own heart. For example, did YOU know the answer to this question?

If a monster earthquake strikes off the Oregon Coast, could the resulting tsunami come all the way up the Columbia River and flatten downtown Portland? —Seismic Citizen

Dr. Know knows!