Abstract: A master valve adapted for insertion in a fuel line to be controlled and a fluid-pressure-responsive actuator responsive to fuel line pressure for maintaining the valve in open position against the resistance of a valve-closing spring; and a normally closed earth-movement-responsive auxiliary valve connected to the fuel line and the aforesaid actuator and functioning in response to a predetermined minimum severity earthquake to open the auxiliary valve and equalize the pressure in the actuator to effect closing of the master valve by its closing spring.