Abstract: A shock actuated safety valve which will shut off gas flow in a supply pipe in the event of a major earthquake. The valve housing has a lower chamber having an inlet and an outlet separated by a tapered valve seat. The upper chamber contains the valve actuating mechanism. The piston, which includes a tapered valve gate and a groove with a ridge at the top, is suspended by seven steel balls which rest on the angled floor of the upper chamber and extend partially into the groove so that the ridge rests on the balls. When the valve is subjected to a horizontal acceleration of a predetermined level the balls are dislodged from the groove, releasing the piston so that it falls until the valve gate sealingly engages the valve seat. Also disclosed is a reset mechanism which includes a reset rod which extends through an orifice in the valve cap and is used to lift the piston back to the open position after it has been activated.