Seismic surveys are used to produce detailed images of the various rock types and their location beneath the Earth's surface. This information is used to determine the location and size of oil and gas reservoirs.
Sound waves are bounced off underground rock formations and the waves that reflect back to the surface are captured by recording devices. Analysing the time the waves take to return provides valuable information about rock types and possible gases or fluids in rock formations. This is similar to the use of ultrasound in medicine.