The subduction area is offshore a pretty good distance. A tsunami from there would have trouble getting into Puget Sound.
The problem is there are assorted other faults on shore, one directly under Seattle. A 7.0 quake on that would be worse for Seattle than a 9.0 on the Subduction zone. 1,100 years ago a quake on the Seattle Fault caused a tsunami on the site of present day Seattle.
Glad I'm in Missouri. I'm not near any ocean, and we haven't had any earthquakes......oh, wait.
The NEW MADRID fault. I guess it's not safe anywhere.
And if Yellowstone Caldera goes, well...
This is a little off topic, but my impression is that there have been a lot of major earthquakes in the past year. Do you know if that's true?
Sri Lanka was offshore a pretty good distance too. The relevant question isn't the distance, but would an offshore generated tsunami propagate into the sound. Basic HS physics taught that waves can turn corners and do other nonintuitive things. If the question hasn't been adequately modeled and studied already, it should be. The roughly third of King county who are honest and pro-American deserve to be saved. With a good computer model one could even test some Science Fiction possible defensive actions. I wonder whether dumping a couple super tankers worth of crude at the mouth of the sound would dampen the wave, if you could pump enough there in time. Or maybe set off some small underwater nukes to interfere with the wave patterns. I doubt either would work, but it would be fun to simulate such. If either would work I presume a majority of King County would vote to die rather than to install the infrastructure required.