Cross-hole seismic surveys have proven value for non-invasive investigations of geological structures and have become the most common method of measuring and detecting hazards beneath the surface.
In a cross-hole seismic survey, acoustic waves are generated in a borehole, then wave arrivals are sensed by geophones in at least two other boreholes at the same elevation. By determining the arrival of the compressional and shear wave, we can calculate their propagation velocities. A velocity log of the materials between the boreholes can be constructed by taking measurements at various depths. Knowledge of the site-specific compressional and shear wave velocities is used to determine the dynamic elastic moduli for the various layers. This method is typically used to characterize the elastic properties of subsurface materials for dynamic structural analysis. Other applications include evaluating anomalous conditions between two or more boreholes, such as abandoned mine workings, sinkholes, sand channels and other stratigraphic discontinuities.