Seismometer Deployed Atop Underwater Volcano

A team led by the Woods Hole Oceanographic Institution installed a novel underwater earthquake-monitoring system atop Kick’em Jenny, an active volcano just off the north coast of Grenada in the Caribbean Sea. The new Real Time Offshore Seismic Station—deployed May 6, 2007, and being tested for the first time—sensitively detects rumblings from the submerged volcano and transmits data within milliseconds by high-frequency radio to a coastal shore station.

“This is the first time that radio telemetry has been used to transmit data from an underwater seismic monitoring station,” said Rob Reves-Sohn, a WHOI marine geologist who heads the project. It will allow scientists to observe the “inhaling and exhaling” of the volcano as it draws in and expels seawater, magma, and superheated fluids, he said. “By putting a seismometer right on the volcano, we will significantly improve our ability to detect precursory seismic activity before an eruption takes place” and help reduce hazards from bursts of volcanic gases or rocks from seafloor avalanches that can generate tsunamis.

“The system essentially acts as a kind of doctor’s stethoscope so we can directly listen to the pulse of the volcano,’’ said Richard Robertson, director of the Seismic Research Unit at the University of the West Indies, who manages the region’s seismic monitoring network. The WHOI research team is also coordinating with the National Disaster Management Agency in Grenada.

A key element of the real-time seismic system is a flexible, stretchy hose that connects instruments anchored to the seafloor with a buoy on the sea surface. The hose is designed to compensate for the movement of waves, tides, and currents, which are notoriously rough around Kick’em Jenny. It stretches more than twice its original length without snapping. Electrical conductors are spiraled through the hose’s wall so that the wires straighten out, rather than break, when the hose stretches. Solar panels on the surface buoy provide power for radio transmitters that send data 4 miles (7 kilometers) to the shore station on Grenada.

The mooring system was developed by engineers Keith von der Heydt and Dan Frye of the WHOI Instrument Systems Develop-ment Laboratory, along with geologist Uri ten Brink of the U.S. Geological Survey in Woods Hole. Spahr Webb of the Lamont-Doherty Earth Observatory of Columbia University designed the seismometer.

Kick’em Jenny provides scientists with a unique natural laboratory to study the activity at a shallow submarine volcano that will one day emerge from the ocean as a new volcanic island. It has erupted at least 12 times since 1939, with the last major eruption occurring in 2001.

The National Science Foundation provided major funding for the project. WHOI and USGS provided additional funds.