Regardless of where you wish to invest in real estate in most of California, as almost the entire State is in a Zone IV seismic area, you need to make sure that the structure/s are constructed or retrofitted to meet the necessary seismic standards for that particular area.
But all that stated there is no guarantee that a major seismic event won't heavily impact any area at any given time. Did the victims of Hurricane Sandy ever imagine suffering such a huge loss just a couple of weeks before?
Here's a couple of links you may want to peruse.
As Grace indicates this and many similar questions are answered by the numerous inspections and disclosures which are provided to the buyer during the escrow period. There should be no "buyer beware"(Caveat Emptor) in a correctly handled purchase.
FYI the report she refers to is approx 60 pages long and provides definitive information on all Natural Hazard possibilities.
To better understand risk in any area, check the natural hazard reports for the properties in question as this will provide you with more information about the zones and locations of active faults in the areas.