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.