Newsroom – California State University, Northridge

CSUN Team Goes Into the Very Deep for Data on Tremors Under the Sea

(NORTHRIDGE, Calif., Mar. 24th, 2010) ―

The stillness of the place was disturbing, like the aftermath of a violent crime. A twenty-something Dayanthie Weeraratne had hiked up Mt. St. Helens to the site of the 1980 eruption whose 24 megatons of thermal energy blasted 1,312 feet of mass off the summit.

Weeraratne was seized by a sense of the power still coiled beneath the devastated surface. “It made me want to know where the energy comes from for a giant eruption like that. I wanted to learn about the energy inside the earth.”

She’d had no prior exposure or much interest in what happens under the earth’s crust—geology was not even offered at her high school—but Weeraratne suddenly was on fire to find answers.

Turns out that geology was her path, and that the answers lay far deeper than she could have imagined that day on the crater.

Weeraratne, now a marine seismologist in Cal State Northridge’s Geological Sciences Department, recently co-directed with seismologist/marine geophysicist Donald Forsyth a joint CSUN/Brown University seismic marine research voyage in the northwest Pacific Ocean. With more than $1.5 million in National Science Foundation (NSF) funding, their aim was “to learn more about the physical properties of tectonic plates and the underlying mantle beneath the seafloor.”

Such research will help deconstruct the complexities of volcanoes and explain how the lithosphere (earth’s rocky outer skin, which forms tectonic plates) forms and cools. It will even tell us more about why earthquakes rumble beneath Los Angeles.

“Earth is the only planet in the solar system that has tectonic plates,” said Weeraratne. “Tectonic plates govern our planet; they’re the reason we have volcanoes. Placing seismometers underneath the ocean can actually help us understand the difference between the earth’s interior and other planets.”

So in October 2009, when most faculty and students were settling into dry, stable classrooms, Weeraratne and CSUN students Cristo Ramirez and Alexander Hanna steamed out of Kaohsiung, Taiwan, on a 20-day voyage aboard the Research Vessel Roger Revelle. Joined by a national team of marine technicians and scientists from Brown University, their mission was to drop ocean-bottom seismometers (OBS) into the Western Pacific Ocean between Guam and Shatsky Rise.

This was no simple toss-object-in-water operation. “It’s easier to put a seismometer on Mars,” Weeraratne said. For starters, the fact-finding seismometers descended to depths where there is “no sunlight and no energy that we know of,” so a case of very expensive lithium batteries—packed in 70-pound stainless steel cylinders three quarters of a inch thick—had to accompany each OBS.

Because Weeraratne wanted data from very old ocean floor plates to compare with more frequently studied young plates, the Roger Revelle’s 18 seismometers—200 pounds each—were dropped into the deepest water in which an OBS ever had been deployed: about 6,000 meters (three miles) down.

Sinking at about 30 meters a minute, it took each OBS between three to five hours to reach the ocean floor. Once in place, the instruments began to record earthquake seismic energy radiating through the earth’s interior, data that will help describe the oceanic plate and crust of the western Pacific. What they record won’t be known until they are retrieved in the fall.

The effort is worth it. Bathymetric data, the ocean floor topography intelligence collected by the OBS, “is the highest resolution data available to anyone in the world.” Even sea floor data from satellites circling the globe cannot compare to it.

OBS data is also expensive to come by; it costs about $40,000 per day to send out a ship like the Roger Revelle. Undergraduate Alexander Hanna, all of 23 years old, would seem an unlikely candidate to guide an awesome 273 foot-long vessel with a speed capacity up to 19 knots and the ability to move sideways or spin in a circle. But guide it he did.

“Alex had to collect and put together all the bathymetric, magnetic and gravity maps for the cruise,” Weeraratne said. He spent months downloading data from previous expeditions, creating a map from his assembled data. “We got on board, and they would ask Alex ‘Which way do we go?’ He would say ‘Go right,’ and we went right. Alex totally came through.”

As did Ramirez, who was known to go without food on his watch so as not to miss deployments or data coming over the monitors. The 24-year-old Ramirez is a master’s degree student in CSUN’s new NSF-funded “Bridge to Doctorate” program (Louis Stokes Alliance for Minority Participation), which prepares minority scholars for doctoral work by opening up hands-on research opportunities. He will return with Weeraratne to retrieve the seismometers, after which the team will process and publish their seismic data.

Ramirez and Hanna held their own among the six sea-tested scientists, four OBS technicians and 25 crew members in the grueling four-hours-on-eight-hours-off data collection schedule. “When a project costs $40,000 a day,” said Weeraratne, “you collect 24/7, with no rest.”

This is not research for wusses. Take, for example, typhoons with 50 mph wind gusts and 40-foot waves. Late in October, the vessel was pummeled for a week by the edge of Philippines-bound Typhoon Lupit, which had made an unexpected turn north. But scarlet sunsets at sea more than compensated, as did a showy meteor shower caused by Halley’s Comet debris. Such natural phenomena were reminders, Weeraratne said, that “I love what I do with a capital ‘L.’”

Still, she gets goose bumps thinking of the responsibility she bore as co-leader of the October expedition. “It’s amazing as a scientist to have an idea …then to be out on the ocean on a multi-million dollar research vessel, dropping advanced instruments, weathering a typhoon, our CSUN students totally involved. And all because of an idea.”

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