In DepthOcean Seismology

Drifting floats detect quakes to plumb Earth's deep interior

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Science  19 Apr 2019:
Vol. 364, Issue 6437, pp. 218-219
DOI: 10.1126/science.364.6437.218

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A versatile, low-cost way to study Earth's interior from sea has yielded its first images and is scaling up. By deploying hydrophones inside neutrally buoyant floats that drift through the deep ocean, seismologists are detecting earthquakes that occur below the sea floor and using the acoustic signals to peer inside Earth in places where data have been lacking. In February, a team of researchers reported using nine of these floats near the Galápagos Islands to trace a mantle plume—a massive column of hot rock that rises up from thousands of kilometers below the islands. The floats, called MERMAIDs (mobile earthquake recorders in marine areas by independent divers), have since been redesigned for longer life, and 18 are searching for plumes in the waters around Tahiti, the team reported last week at the annual meeting of the European Geosciences Union. This August, another 30 MERMAIDs will be added to the South Pacific project. MERMAIDs could be a general purpose tool for ocean observations, as well. The hydrophones can also detect the sound of rain or whales, and MERMAIDs can be outfitted with other environmental or biological sensors.