The Seattle Fault runs East-West straight through the city of Seattle (naturally). In the last 3500 years, there have been 7 earthquakes of more than magnitude 7, and the last occurred about 1100 years ago. So if you do the math, it appears that it is about 400 years overdue.
Here is a satellite image of Seattle:
Since the fault goes under the ocean, if an Earthquake occurs, it will generate a local Tsunami.
Some scientists made a simulation of the Tsunami after such an earthquake at:
Here is the simulated Tsunami at it's widest ( the largest area is about 3miles wide, and 2-2.5 miles long)
It helps to overlay the two.
Here is an overlay with a map of Seattle: