Downhole Seismic investigations are similar to the CH method, but they only require one borehole to provide shear velocity and compressional velocity wave profiles. The DH method uses a wooden beam on the surface to generate shear and compressional waves. A pair of three component geophone receivers, coupled each either, are lowered downhole, spaced 1 meter, to receive the P- and S- wave energy. This method is performed in accordance with ASTM D4428-D4428M-00 Standard Test.