Abstract: A device for generating in the ground longitudinal and transverse acoustic waves by a mass striking a target element coupled with the surface of the ground. The target element is recessed in a central part thereof and have an inner wall slanted with respect to the vertical in the form of, for example, a truncated cone. The mass is fixed to the end of an arm pivoting with respect to a support structure in the form of a parallelepipedic cage, which is movable by a cylinder between a high transport position and a low position in which the target element is coupled with the ground a drive causes raising of the mass by pivoting the arm with the geometry of the assembly being calculated so that the mass strikes the inner slanting faces perpendicularly thereto, and thus creates both P and S waves.

Abstract: A mixed device for successively generating in the earth, at the same location, longitudinal and shear waves is disclosed. The device comprises in association a target coupled to the earth surface and having a first striking face substantially parallel thereto and at least one second striking face substantially perpendicular to said first striking face. A guide tube is adapted to be positioned above the first striking face and perpendicularly thereto, and a movable weight is slidable in the guide tube and adapted to strike the first striking face. At least one hammer is articulated to a support rigidly secured to the guide tube and adapted to strike one second striking face of the target. Directional coupling means connect the guide tube to the target in such a manner that the weight sliding in the guide tube directly impinges the first striking face, but such that the guide tube is substantially released from the effect of the hammer impact on a second striking face.

Abstract: The improved device for generating acoustic shear waves in the earth comprises a target member adapted to be coupled with the earth and provided with two lateral striking surfaces on which impinges a hammer pivotably mounted on a platform; the target member is connected through damping means to a cage supporting the platform, the hammer and its actuation means, said cage being displaceable with respect to the frame of a carrying vehicle between a position of contact with the earth of the target member and a lifted position thereof, the striking surfaces being inner walls of the target member.

Abstract: Multiple shocks of a vertically falling mass against a target member coupled with the earth are prevented by holding the mass and retaining it above the target member after its first bounce. This retention is accomplished by means of deformable elements laterally pressed against the mass body by jack rods actuated in response to a control signal produced by a sensor at the moment of the first impact of the mass.

Abstract: A device for preventing secondary impacts of a mass against a target member, as used in particular for generating shear waves in the earth, is provided. The mass is secured at the end of a pivotable rigid arm actuated by driving device, and the driving device adapted to block the fall of the rigid arms, comprises a cam co-operating with a pawl when it registers therewith and with a flat part of the cam with the registering conditions occurring only after the first impact of the mass and its bounce against the target member.

Abstract: A mobile device is used which includes a target-member adapted for coupling to the earth and a means for striking the target- member so as to generate acoustic shear waves.The target-member is coupled to the earth through a deformable coupling member secured to the rigid frame of the target- member, the coupling being enhanced by the combination of a suction means and a network of channels arranged on the face of the coupling member which is in contact with the earth, whereby a partial vacuum is created between the coupling member and the earth.

Abstract: A mobile device for generating acoustic shear waves comprises a structure provided with at least one axle with wheels mounted thereon, said axle being displaceable with respect to at least a part of the structure.The mobile device has mounted thereon a target-member displaceable from a position suitable for transportation to a working position where it is in contact with the earth, and means for striking the target member, when in working position, by means of a mass, to produce an impact thereon.The target member is provided at its upper part with tracks for the wheels of the axle so that the wheels can be driven, by displacing the respective axles, from a position of contact with the earth to a position where they bear on the target member with the weight of at least a part of the structure.

Abstract: A device for generating shear waves in the earth for seismic prospectives, comprising a target member coupled with the earth, a vehicle carrying a mass and means for driving and guiding the mass along a direction perpendicular to the striking surface of the target member and parallel to the earth surface, said means comprising a toothed wheel in mesh with a driving chain and a counterweight for balancing the mass. According to a particular embodiment, the target member is so designed that at least a part of the vehicle weight can be applied thereon.

Abstract: Device for generating shear waves in the earth for seismic prospecting, comprising means for striking with a mass a target-member coupled to the earth, said means including means for lifting and shifting said mass with respect to the target member, an electromagnet for intermittently locking it in an upper position and releasing it abruptly and means for adjusting the stroke of the mass from its upper position to its lower position where it impinges the target member.