I was in SF during the Loma Prieta earthquake in '89.
Working for the telco, at the time, I had some repair jobs on Treasure Island. The Bay Bridge collapse was on the Oakland side and although the bridge was closed to through traffic, the suspension span was open to Yerba Buena and Treasure Island. Only the far right lane was open and when I went over it, my telco van was the only vehicle on it.....going and coming back into the City. That felt a little strange since it was usually very busy. Pac Bell never went down, only too many people trying to get dial tone caused people to think the systems were down. Afterwords we had dozens of no dial tone tickets that were 'found ok'.
There was a strong one in SF in '57 too --- I was 5yrs old........I wonder if Jerry Lee Lewis' "whole lotta shakin goin on" was inspired by that since it was written at that time.