* Astronomy

A team of seismologists led by University Collage London’s Dr Frederik Simons (UCL Earth Sciences) and including scientists from the Scripps Institution of Oceanography and Princeton University, has invented a submersible device that can detect earthquake waves in previously uncharted geographical areas.

Nicknamed MERMAID (Mobile Earthquake Recorder in Marine Areas by Independent Divers), the device is planted at sea and spends most of its time at depth, surfacing occasionally. It is equipped with a hydrophone, which records water pressure variations into which compressional seismic energy is converted at the sea floor.

Untethered and passively drifting, the float surfaces on detection of a seismic event, determines a GPS location and transmits the waveforms to a communications satellite. The float is cheap to operate, and data can be available in real time.
Currently, seismologists rely on data provided by receivers mainly on dry land, which produces uneven coverage of global seismic activity. In fact, large areas of the globe’s oceans are uncharted, resulting in many undetected seismic events. Seismologists analyse the waveforms of seismic waves to determine the structure of the Earth's interior by a procedure known as seismic tomography, a technique akin to medical CAT scanning. The lack of recorded earthquakes results in ‘blank spots’ in our knowledge of the deep Earth.

The barriers to this coverage have until now been financial – the existing alternatives to MERMAID, such as placing seismic stations on the ocean floor, are very expensive. However, Dr Simons is proposing that a global network of MERMAIDs floating around the oceans could be a cost-effective solution.

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