The application of geophysical survey techniques to site investigations for civil engineering purposes. Common investigations include: finding the depth to bedrock for foundation studies; determining the rippability of material for excavations; measuring the degree of fracturing of rock; the detection of underground fissures, cavities, and mineshafts; the location of pipes; and, in a marine environment, the determination of the strength of sediment infill and the detection of dangerous near-surface gas pockets before drilling with a jack-up rig.