Seafloor geodetic instruments and waveglider receiver

At left, seafloor transponders rest on the deck of a reasearch vessel, ready to be placed on the seafloor. Receivers on wavegliders, at right, pick up the signals from the transponders and record their precise location using GPS. This is called seafloor geodesy. Scientists use the data to study how much the seafloor moves, in areas where tectonic plate movement can trigger earthquakes.