During the earthquake in 1906 San Francisco was destroyed. Ever since then the Bay Area has increased from 400,000 to 7.7 million people. San Francisco along with Daly City, Santa Rosa, Sunnyvale, and San Jose were the worst cities to be during the 1906 earthquake. If that earthquake were to happen again, the shaking damaged would be greater. One of the tips they mentioned to make your home or apartment more resilient is retrofitting.

For more info, please read the original article by Temblor:
http://temblor.net/earthquake-insights/the-5-worst-and-5-best-places-to-live-in-the-s-f-bay-area-if-the-great-1906-earthquake-recurred-today-8603/