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Real-Time Seismic Monitoring Station Installed Atop Active Underwater Volcano

May 11, 2007

This week, researchers will begin direct monitoring of the rumblings of a submarine volcano in the southeastern Caribbean Sea. On May 6, a team of scientists led by the Woods Hole Oceanographic Institution (WHOI) installed a new underwater earthquake monitoring system on top of Kick'em Jenny, a volcano just off of the north coast of the island nation of Grenada. The new mooring- and seismic monitoring technology will significantly improve the ability of natural hazard managers to notify and protect the island's residents from volcanic eruptions and tsunamis.

Part of a project to develop new technology for earthquake monitoring in coastal areas, the Real Time Offshore Seismic Station (RTOSS) uses an ocean-bottom seismometer (OBS) deployed directly on top of the volcano—250 meters beneath the sea surface—to collect real-time data from Kick'em Jenny. RTOSS employs a special mooring design that allows seismic data to be transmitted by high-frequency radio to a land-based observatory in the village of Sauteurs. The data will reach the shore within milliseconds of being collected, which will significantly improve the ability of researchers to monitor seismic activity as it happens, a basic requirement for reducing hazards from volcanic gas and rock bursts and from tsunami-generating seafloor avalanches.

"This is the first time that radio telemetry has been used to transmit data from an underwater seismic monitoring station," said Rob Reves-Sohn, an associate scientist in the WHOI Department of Geology and Geophysics and an RTOSS project leader. Scientists will be able to observe the "inhaling and exhaling" of the volcano as it draws in and expels seawater, magma, and superheated fluids. "By putting a seismometer right on the volcano, we will significantly improve our ability to detect precursory activity before an eruption takes place."

The WHOI research team is coordinating with the National Disaster Management Agency in Grenada and the Seismic Unit of the University of the West Indies so that the data is incorporated into the existing regional monitoring network.

A key element of RTOSS, developed by engineers at WHOI, is the flexible, stretchy hose that connects the seafloor anchor and instruments to the buoy on the sea surface. This hose is designed to compensate for the movement of waves, tides, and currents (which are notoriously rough around Kick'em Jenny), and stretches to more than two times its original length without snapping. Electrical conductors are spiraled through the wall of the hose so that the wires straighten out, rather than break, when the hose stretches. A surface buoy on the end of the mooring uses solar panels to power the radio transmitters that send the data approximately seven kilometers (four miles) to a shore station near the coast.

The mooring system was developed by engineers Keith von der Heydt and Dan Frye of the WHOI Instrument Systems Development Laboratory, along with geologist Uri ten Brink of the U.S. Geological Survey. Other team members include Spahr Webb of the Lamont-Doherty Earth Observatory, who designed the seismometer, and Richard Robertson at the Seismic Research Unit of the University of the West Indies, who manages the regional monitoring network.

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 is the only "live" submarine volcano in the West Indies, and it has erupted at least twelve times since 1939. The last major eruption occurred in 2001.

The Woods Hole Oceanographic Institution is a private, independent organization in Falmouth, Mass., dedicated to marine research, engineering, and higher education. Established in 1930 on a recommendation from the National Academy of Sciences, its primary mission is to understand the oceans and their interaction with the Earth as a whole, and to communicate a basic understanding of the ocean's role in the changing global environment.

Major funding for this project came from the U.S. National Science Foundation. Additional funds were provided by Woods Hole Oceanographic Institution and the U.S. Geological Survey.

Woods Hole Oceanographic Institution