The Deep-Ocean Mass Spectrometer is on its deployment mainframe prior to lowering it to more than 1,000 meters water depth off Costa Rica from the R/V Atlantis. Standing beside it, from left, are Gary McMurtry, associate professor of oceanography at the University of Hawaii; Lloyd French, associate professor at the Hawaii Institute of Geophysics and Planetology at the University of Hawaii; and Bernhard Chapligin, geoecology graduate student at the University of Karlsruhe, Germany.

UH scours sea floor
for catastrophic clues

Scientists look to dissolved gases
for signs of a big event

University of Hawaii scientists will be analyzing chemical data to warn of potentially catastrophic events such as earthquakes or landslides.

"The concentrations of dissolved gases we can detect with the spectrometer, like methane, carbon dioxide, hydrogen, helium, etc., can respond to changes in the reservoir rock pressure," Gary McMurtry said by e-mail from Costa Rica.

"Sometimes these pressure changes, usually a slow buildup, can presage a tectonic event," he said. "A good example is the chemical signals detected in the ground waters a few weeks before the deadly Kobe earthquake in Japan in 1995."

McMurtry, associate professor of oceanography and geochemist, and Lloyd French, associate professor with the Hawaii Institute of Geophysics and Planetology, deployed the Deep-Ocean Mass Spectrometer with the Woods Hole Oceanographic Institution's research vessel Atlantis and manned submersible Alvin.

They lowered it about 3,300 feet onto the sea floor over active venting areas marked by bacterial mats and vent fauna. It will remain there at least four months sampling the chemistry of the cold seep vents.

McMurtry said the Costa Rica margin was chosen for the instrument's initial field test because it allows close collaboration with other scientists studying the time-series characteristics of fluids beneath the sea floor there.

"We can therefore get 'ground truth' information on the same chemical compounds we are measuring and internally recording with the spectrometer as well as potential correlations to geophysical parameters being monitored, like fluid flow and seismicity," he said.

The region is similar to the active Sumatran collision zone that caused the devastating Dec. 26 tsunami, McMurtry said. It is extremely active because the Cocos tectonic plate is colliding with the Caribbean plate and there many active arc volcanoes on land, he said.

Basically, he said the UH team is doing exploratory research "with an endurance test of novel equipment thrown in.

"The whole idea is to obtain a time series (of chemical compounds) so we can begin to see the natural variability," he said.

"That in turn may reflect subsea-floor processes such as response to regional stress changes or to bottom water temperature changes, tidal forcing, etc."

The Deep-Ocean Mass Spectrometer will record data internally that must be retrieved. But the goal eventually is to be able to characterize the water's chemistry and relay the information in real time from the sea floor, McMurtry said.

He said there are already instruments that are much simpler and cheaper to deploy than the spectrometer that can record past events, mainly by taking and storing samples of the fluids to be analyzed in the lab after the instrument is recovered.

"Our goal is to provide quantitative chemical data in real time or as close to real time as possible with current technology," he said.

To accomplish that, he said, the system software must be changed to transmit the data.

"Once at the surface, data could be transmitted anywhere via cell phone or satellite."

McMurtry has investigated volcanoes and prehistoric landslides resulting in tsunamis in Hawaii. French formerly led projects for NASA's Jet Propulsion Laboratory. Their team includes Bernhard Chapligin, a geoecology graduate student trainee from the University of Karlsruhe, Germany.

The Deep-Ocean Mass Spectrometer has a large external battery and a Continuous Aqueous Transport system that can measure fluid flow rates and the chemistry of fluids stored over the deployment period. They are part of a combined underwater mainframe assembly.

The instrument was developed at the UH-Manoa's School of Ocean and Earth Science and Technology.

McMurtry said the researchers used the unique underwater technological assets of the school's Engineering Support Facility, "and we owe a major debt of gratitude to their engineers, in particular James J. Jolly and David Copson and machinist Michael Cole of the SOEST Machine Shop."

The spectrometer will be retrieved from the sea floor in four months by the Quest, a remotely operated vehicle from the German research ship Meteor.

The study is part of a larger collaborative research effort funded by the National Science Foundation.

UH School of Ocean and Earth Science and Technology

| | |
E-mail to City Desk


© Honolulu Star-Bulletin -- https://archives.starbulletin.com