If you are, perhaps, thinking of buying (or maybe even renting) a place in the Bay Area, you might want to play with the Association of Bay Area Governments shaking map system. It lets you zoom in on different neighborhoods and then select earthquakes at various faults to see the possible destructive scenarios. The color coding is fairly intuitive, too -- red is bad. Here's part of Mountain View under a couple of possible earthquake scenarios.
A quake on the Mount Diablo fault:
Most of Mountain View is doing just fine here, with light to moderate shaking.
A quake on the entire Hayward fault:
Now the shaking is "very strong" East of Central, and "strong" everywhere else. I haven't checked yet to see how these ratings correlate with buildings actually falling down.
Now, the entire San Andreas fault going off:
That's more "very strong" shaking with a spur of "violent" shaking down the middle. Ouch.