To provide long-term regular monitoring of an underground area, a stationary seismic transceiver device is positioned at the production site so that stable operating conditions are maintained at all times, i.e. constant transmission/reception locations, constant earth coupling quality, etc. The device comprises a plurality of seismic sources (S1 ... Sn) placed in fixed locations on the surface or buried at a shallow depth, on either side of a production shaft (1), and one or more receiver assemblies (R) permanently mounted on the surface or in one or more wells. Explosive sources, positive-pressure hydraulic sources, electro-mechanical sources, etc., may be connected to a power supply facility (3). They use an explosive gas mixture optionally comprising a component drawn from the area being monitored, and a pressurised fluid transmitting hydraulic shocks or vibrations, etc., via buried ducts or cables (2), and the power supply to and operation of the sources are controlled by a central control and recording station (4). The device is useful for monitoring the filling of an underground cavity, e.g. for gas storage.