Residing an old house in seismic zone

My home was built in 1910 and has the original plank sheathing. It is in a seismic zone, Seattle, and I am wondering if this sheathing should be replaced, renailed, or covered with plywood during residing for additional shear strength. If not I’ll just use foam board.
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Adding structural sheathing would certainly improve your home's seismic resistance, but you'd have to get a structural engineer to tell you whether you actually need it or not.
Another option is to add 1/2" plywood to just the first 4' of wall at each corner. Then cover the plywood with, say, 1-1/2" foam and use 2" for the rest of the wall.
James,
Another Layer of sheathing will definitely increase the resistance to earthquakes. The most common vulnerability of older west coast houses though is their connections to the foundation below , and any knee walls to the house above. If you are going to add shear strength by re-sheathing, I would consider addressing those areas as well.
Thanks. I did the knee wall retro fit on my previous home and in my current home the previous owners retrofitted in 2016. I'll talk to an engineer when I'm ready to reside, sounds like it is a good idea.