Not really related to your main point, but I believe this is a common misconception about earthquakes. S.F. may be likely to have an 8.0 earthquake once every 300 years (I made these numbers up), but just because it's been 400 years since the last one doesn't mean a big one is more likely now. It's more like any given year has a 1/300 chance no matter how long it's been since the last one.