Having lived in the San Gabriel Valley for several years and the San Fran Bay area for the first 21 years of my life I can honestly say that I don't ever remember there being a small one leading to the "Big" one. I know they say it can happen, but I don't remember any that were significant.
I can tell you the freakiest thing tho, once I was on the phone in our house in Temple City talking to a friend in Pomona. All of a sudden she says, we are having an earthquake and it took a few seconds then it hit where I was. Now, that was weird!
I have seen damage from small quakes in the late 80's early 90's. All the toilets in our townhouse in San Gabriel broke once from a small quake centered in Sierra Madre and then in the Whittier quake we had no damage living in Arcadia but many of our neighbors did.
We had moved here to NV when Northridge came along, thank goodness. My insurance agent used to tease me, I have earthquake insurance on my house here in NV, it doubles my homeowners policy but when things started shaking here a year ago I was the only one on my block who was not as worried about the "big" one