Canie, I believe that along the southern California margin, faults form folds, not the other way around. Elsewhere, you can get folds related to diapirism, and this diapirism can make faults around it. There might be some diapirism of serpentine in the Franciscan Complex, but otherwise, to get a very broad anticline, there is a wide fault slipping at depth. So, yes, the fault is beneath the fold. Earthquakes like Coalinga (1983?), and Northridge 1994 were on these types of faults. Chris