What part of Japan do you live in? At least in Nagoya there is at least one "Showa" house per block. They are knocked down when their inhabitants (generally older people) stop living in them, but it's not hard to find them.

It was known that older houses were dangerous in earthquakes (I believe the safer building code dates from the 80s), but no one was really worried about it until the Kobe earthquake where most damage was borne by older buildings.