Most contractors are aware of seismic building requirements i.e. tie downs, shear paneling, strapping, etc.. Additionally, you must pull permits for most remodeling and all room additions or structural alterations. So right there you have the planning department on your side looking out for your best interest.
As far as living near a fault line? Most of California is in a Zone 4 seismic reach. So if that's a major concern you may want to check with the http://www.consrv.ca.gov/cgs/rghm/ap/Pages/index.aspx or the http://earthquake.usgs.gov/earthquakes/recenteqsww/ to determine where active fault lines are. I believe the Sacramento area is not in a Zone 4 seismic area.
As for building I suggest you discuss that with your contractor and give a call to the City Building Department.