The Northridge quake occurred on a fault that was previously unknown and had never been active in historic time. It was the costliest quake in American history. My house was further from it than freedumb's but the temblor packed a terrifying wallop. I'm still fearfully waiting for the next "aftershock." Sometimes they don't occur for decades.
Published accounts by Caltech seismologists at the time mentioned the entire L.A. Basin is riddled with similar undetected faults that will eventually flatten all the expensive development on the surface.
Those of us who live in pleasant coastal subduction zones should accept as a fact of life that the Devil can have a nightmare any time. When he shifts position and squirms, all Hell breaks loose on the surface.
Pretty creepy when you consider it inevitable, not theoretical.