The detectors used for seismic exploration work are called geophones since they are
used to "hear" echoes from the earth underneath. Sometimes, they are called seismometers
but this term is more often applied to long period seismographs used for recording natural
earthquakes. The term "detector" applies to all types of seismic-to-electrical transducers.
From what has been said before, it will be clear that they can be classied into two main
groups: motion-sensitive, mainly for land operations, and pressure-sensitive for operations
in water (or fluids), be it for marine seismic work or in the mud column of a borehole, for
well-shooting or a VSP. Pressure-sensitive geophones are also called hydrophones.