Will plywood between foam board insulation be prone to moisture condensation?
Where in the world do you live? Most earthquake zones are temperate climates in the US. It sounds like your sealing may create more of a problem as you will end up with a double barrier or even 3 if the house is wrapped trapping moisture. 
The Pacific Northwest in the US is one of the cooler earthquake zones but also the wettest and this sandwich would setup a great home for mold. The insulation in the walls with an additional layer of plywood would help seal. I think the extra layer of foam is asking for trouble long term.