Abstract: A seismically triggered valve is designed to shut off gas supply during an earthquake. A valve member is pivoted within a valve body, the valve member being mechanically movable to the open position by a plunger. A magnet is fixed to the valve member, and a ferromagnetic ball is free on a concave surface. The center of the concave surface is aligned with the magnet; but, when the valve is shaken the ball moves and releases the magnet. Gravity moves the valve member to the closed position, and the valve member is held in the closed position by magnetic attraction.