"It's required in Los Angeles County," said my landlord.
I found out about it when we didn't have any hot water one morning. It turns out our earthquake valve shuts off for garage doors, cars in the driveway, garbage cans and fence gates slamming, too. The gas company charges $60 to come and turn it back on again.
I was in an earthquake once, years ago in San Francisco, a little one that sent me into the street in the middle of the night, with all the other non-Californians. For a long time afterwards, I felt that my bed was moving all by itself. The house itself was moving. It was a creepy feeling.
Sometimes I ask people what the big Northridge earthquake was like in 1994. "I saw the freeway rippling like the ocean," one girl said.