Thats one thing I don't understand. Why people would live in such a dangerously high risk area. Not just talking about California. But so close to volcanoes, slap bang on fault lines. I'm not referring to people individually, but why people would chose to pick an area like that to expand a city, for businesses etc. The home insurance would be so high aswell I guess, as well as insurance for businesses etc.
YouTube - (BBC)How the Earth Made Us 1-Deep Earth -Part 1
That BBC documentary pretty much explains why people have settled near fault lines.