Self-insuring is probably not going to fly with your mortgage lender. If nobody can get a mortgage, and everyone has to self-insure, it's going to 1) drive down housing prices (fewer cash buyers) and 2) guarantee that only people of pretty substantial means can afford to live there (even with lower prices, most people can't come up with a cash payment for a house).

Brick buildings don't do well with earthquakes. California also happens to sit on a major, active fault line. While it is technically possible to make a brick or stone building earthquake-proof, I would imagine it's cost prohibitive for large scale single-family housing projects. Apartment towers are already built with a multistory steel-reinforced concrete base that is built to withstand earthquakes, but it would increase costs significantly to build to the top like that.