Son-o-MERMAID takes to the waters

SEISMIC WAVES CAUSED BY EARTHQUAKES can tell us a lot about the makeup of the Earth’s crust and mantle. Yet we lack seismic readings from the regions under the world’s oceans, which cover 70 percent of the planet’s surface. To address this data gap, Associate Professor of Geosciences Frederik Simons and colleagues developed ocean-going autonomous buoys called MERMAIDs (Mobile Earthquake Recording in Marine Areas by Independent Divers) and, in a paper published on Aug. 20, 2015, in Nature Communications, reported that the divers can recognize earthquakes and transmit seismograms more or less in real time.

The divers are equipped with a hydrophone to detect acoustic signals generated by seismic waves. The MERMAID drifts as deep as 2,000 meters under the surface until it detects an earthquake. Then it ascends to transmit the recorded waveform and its GPS position.

Simons and colleagues at the University of Rhode Island are now working on the next-generation buoy, which they call Son-o-MERMAID. After its maiden voyage three years ago was disrupted by Hurricane Sandy, the float is once again being tested and will be ready for deployment in the next few months. Compared to its progenitor, the new float has better position awareness and real-time communication capabilities because part of the instrument is always above water, and, in addition to batteries, has solar panels that power a vertical array of hydrophones.

The research is supported by the A.H. Phillips Instrument Fund at Princeton University and by the National Science Foundation.

–By Catherine Zandonella