What are seismic airguns and how are they used in seismic surveys?
A seismic airgun unit is basically a large piston with a plunger that discharges a compressed air bubble into the water at considerable pressure thereby creating a sound source. The timing of discharge is controlled by solenoid valves and the air source is an appropriate compressor attached to the airgun. Over the years there have been many improved modifications and patents on airgun technology. A survey of “Patents-on-Line” reveals that there are more than 250 registered patents on airgun technology in the USA alone. Deep water marine seismic surveys are conducted using vessels capable of towing one or more seismic cables with multiple airguns (arrays) and hydrophones that are towed behind the ship following a transect pattern over selected target areas. The cables are known as “streamers”. The air gun array is towed about 6 to 10 meters beneath the sea surface. A single vessel moving at a speed of 8 knots may tow anything up to 16 streamers, each 6 km in length, spaced 50–150 m apar
