Abstract: A safety valve for automatically shutting-off fluid flow in response to excessive vibration specifically indicated for use as a seismically actuated gas valve. The inlet and outlet ports are separated by an horizontal septum having an aperture defining a circular valve seat. A ferrous ball is suspended above the aperture by a permanent magnet housed in a spherical member adjustably mounted in the roof of the valve above the aperture. The member houses a bulb-type level indicator used to adjust the position of the magnet in order to compensate for any askew position of the valve resulting from the orientations of the connecting pipes.