having done construction on both coasts, i can say that CA code has many more enforced seismic provisions. required structural connectors and fasteners for use, required nailing schedules, plastic insulators on wiring staples, shear and retaining wall requirements, etc. they also require older buildings to be retrofitted with seismic upgrades if a structural permit is needed for new work. we are fortunate that our 110 yo house has diagonal rough cut 1x8 throughout the interior, under the sheetrock.