Usually, the seismic source and geophones are located at or very near the surface. Most borehole surveys, such as conventional well-velocity surveys, measure only the traveltime of the first energy. In contrast, vertical seismic profiling (VSP) involves recording the complete waveform at regularly and closely spaced depth stations. Extracting velocity information is only one of the objectives of VSPs. They became more common in the late 1970s and 1980s, but the cost of occupying a borehole for the time required continues to deter their greater use.