Cross-Hole and Down-Hole V_s by Mechanical Impulse

Two techniques for determining in-site shear and compressional wave velocities using mechanical impulse sources are shown to provide valuable information pertaining to the elastic properties of rock and soils. Both techniques utilize the reversal of first motion of shear waves to determine the shear wave arrival times. A description and case history of a shear wave-generating mechanism for use in a cross-hole configuration is presented. An instrumentation scheme for determining seismic wave velocities in deep boreholes using the down-hole technique is described, and a case history of the use of the technique in a 1,200-ft (370-m) deep borehole is presented. Techniques for estimating strain and damping from the seismic records are also considered.