Institut Francais Du Pe'trole

Compagnie Generale De Geophysique

Andre James

Pierre-Claude Layotte

Jean Laurent

Jean-Claude Dubois

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.

Mixed device for generating longitudinal or shear waves

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.

Device for avoiding multiple bounces against a target of a mass _falling

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.

Mobile device for generating acoustic shear waves

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.

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Royan, France

Andre James