Southern California Edison states the station was “built to withstand a 7.0 magnitude earthquake directly under the plant”. Additionally, there is a 25-foot tsunami wall to protect the plant from a rogue wave that could be potentially generated by the active fault 5 miles offshore. The closest tectonic fault line is the Christianitos fault, which is considered inactive or “dead”.
http://en.wikipedia.org/wiki/San_Onofre_Nuclear_Generating_Station
The wall can be seen in the enlarged photo below:
http://upload.wikimedia.org/wikipedia/commons/7/7d/Aerial_San_Onofre_Generating_Station_May_2012.JPG
Thanks. Withstand 7.0 is good. The wall is good, but it looks like they carved out a spot to build it down in the flood zone, instead of building above it. That seems odd.