this is partially because of the earthquake codes. a major earthquake tends to happen once every generation, and building codes tend to get updated after them.

this is partially because of the earthquake codes. a major earthquake tends to happen once every generation, and building codes tend to get updated after them. If you buy a house not compliant with the current rules it is more likely to kill you; most damage in the 1995 Hanshin earthquake, for example, occurred to buildings predating the 1981 building code.