If your home is a newer home, it may have an earthquake actuated gas shutoff valve installed, as many city and county regulations were changed to require it of new construction. As gas leaks are frequent after a large earthquake and can become dangerous quickly, this is a very helpful device for the safety of you and your home in a larger earthquake.
How do you know if you have one? Look at your main gas meter for a small device that looks like the one in the photo above. If you don’t have one and want to install one, you must only install a state approved device and it must be done by a licensed plumber for safety.
Western Mutual Insurance Group 