Abstract: Disclosed is an apparatus for generating seismic waves in a well bore, which apparatus includes a tubular expandable and contractible outer anchor wall, a seslf-contained anchor setting hydraulic system to expand the anchor into anchored position in the bore hole, a self-contained vibrator hydraulic system operable to cycle pressure impulses to the interior of the tubular expandable and contractible outer anchor wall effective to produce and radiate seismic waves, a cable including electric lines for locating the apparatus in the well bore, and switch means at the surface for controlling the operation of the apparatus. The apparatus is useful for geophysical investigation including vertical seismic profiling and cross hole tomography.