Downhole Seismic :
Downhole seismic surveying is an important field method for determining key in-situ subsurface information for earthquake engineering and other geotechnical site investigations. Downhole Surveys are undertaken to measure the vertical distribution of seismic velocity in the earth. Such surveys provide detailed information on stratigraphy and the engineering properties of subsurface soils and rock that is not available from surface seismic surveys. Shear-wave velocity profiles obtained from downhole surveys are routinely incorporated in site response modeling for earthquake hazard evaluation and structural design.