There is not a significant tsunami risk from a Cascadia subduction zone earthquake in Seattle, due to its topography and distance from the fault. The biggest ri

There is not a significant tsunami risk from a Cascadia subduction zone earthquake in Seattle, due to its topography and distance from the fault. The biggest risk in that regard is from the Seattle fault, a thrust fault, that runs through the middle of Elliott Bay, which can both generate large water displacements and can cause large subsidence of the land (i.e. it can literally sink a dozen feet during an earthquake). Seattle is geographically very vertical, and heavily shielded from the open ocean, which limits the tsunami effects. The real risk is civil engineering in nature. While the fault is some distance away, it will shake hard and for a long time. Unreinforced masonry will probably be destroyed, and Seattle has a lot of old masonry in some neighborhoods. Some older structures not up to the current seismic code will likely fare poorly. Seattle has had enough local 7+ earthquakes that a distant offshore 8-9 won’t feel too much different, but the shaking time will be much longer. Landslides are undoubtedly a risk. Portland will likely fare much worse than Seattle. A modern steel or wood-framed building constructed in the last 20 years will very likely survive almost anything, they are built for it. Older steel and wood buildings that are still standing have already been through some earthquakes; not as large but they won’t immediately collapse. The real problem will be restoring infrastructure in the aftermath.