I agree with the others, the fault lines are everywhere. I live in Arizona. While we have felt some earthquakes here, fingers crossed, nothing big has occurred.
We just moved here from spending 4 years living next to Utah Lake. About a year before we moved, we learned there was a major fault line running right down the middle of the lake. There is also one along the Wasatch front. I think some people just don't know it! I know we didn't and following a small quake with the epicenter near our home, we got the heck out of there.
I am sure a lot of the reasons run from there is risk everywhere, to they just don't know it, to people can't afford to just pick up and leave.
It's really scary. My dad is now living in our house and claims that when the big one hits he'll ride the house down the mountain and into the lake. It paints a funny picture, but it wouldn't be funny at all in reality.