Indeed. Did your place have one of those valves with a ball bearing that would shut off when moved with force? Evidently running a bicycle into one of those will also trip the valve.The Annoyed Man wrote:
When you have lived in earthquake country as long as I have, this stuff is second nature.
The reason to shut off the gas supply to your house would be if there was damage at some point past the gas meter and you had a gas leak. As TAM said, this is a common procedure when encountering an earthquake.