Project measures stability of earth's core
By Beverly Creamer
Advertiser Education Writer
Battling 20- to 30-foot ocean swells 1,000 miles from Hawai'i, the deep-sea drilling vessel Jodies Resolution is floating in the middle of the Pacific attempting to sink a hole deep into the ocean floor so scientists can trace even the slightest earthquake generated on the bottom of the sea.
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"They're still drilling," said University of Hawai'i-Manoa geology professor Fred Duennebier, who has been monitoring the vessel's progress hourly since it went to sea the day after Christmas.
Dr. Fred Duennebier, a UH professor of geology and geophysics, says a new seismometer that will be put in a drill hole under the ocean will measure even small quakes.
"They can drill in 10 to 12 foot waves, but anything bigger they have to stop," said Duennebier, principal investigator for the project. "The pipe is going up and down 30 feet."
The 450-foot ship — operated by Texas A&M University for the National Science Foundation — hopes to prepare a site for a new seismometer that would vastly improve the ability to detect earthquakes and the giant tsunami waves they can generate.
"There's a seismometer out there which we built in 1998," said Duennebier. "It's about three feet under the bottom. But by putting it in a drill hole, it should be a great deal quieter. And the quieter it is, the smaller the earthquake you can see."
The point of all this is not to raise a warning about the latest tsunami — the National Oceanic and Atmospheric Administration does that — but to gather geological data on the material under the ocean floor clear to the earth's core.
Measuring how fast seismic waves travel helps identify the kinds of rock that exists and what that means for the core's stability.
The operation is part of an on-going project of a dozen academic institutions around the world, and brings together centers in half a dozen countries. The ship has been circling the globe since 1968, drilling holes in the ocean floor to advance hundreds of scientific endeavors. UH has its proposals accepted about every other year, said UH geology professor Gregory Moore, a marine geophysicist involved in some of the analysis.
The latest drilling site is known as the Hawai'i-2 Observatory, a point halfway across the Pacific above an undersea telephone cable that was laid in 1983. While the phone cable has since been replaced by newer fiber optic technology, it still has 50 or 60 good years left, said Duennebier, and could keep the unique earthquake-monitoring research system online well into the middle of the century.
"We get power from the cable and send our data back over it," Duennebier said.
As Duennebier sits at his desk in the Department of Geology and Geophysics at the UH, he can monitor the sound of the drilling operation hundreds of miles at sea. On his computer, a series of wiggly lines in lime, chartreuse and turquoise make a graphic picture of the ocean waves under the sea, even the songs of whales.
"You can tell those are whales because every so often they come to the surface," he said, pointing to a wiggle of a different hue.
But most of the wiggly lines are earthquakes — an everyday occurrence on the ocean floor. And in every size.
"When they get big they literally cover the whole screen. They get huge," he says. But in the past two years, he hasn't seen one to worry about.
"Right now I'm looking at the noise they're making by drilling into the hard rock," he said, flipping between the images offered by a dozen ocean-floor sensors. "What I look at is the motion of the ground about a mile away" where the current seismometer sits plugged into a junction box attached to the old cable."
The drill ship looks like an oil rig sitting atop a mammoth research vessel. The drilling tower extends high above the deck, and a hole in the middle of the deck — called a "moon pool" — allows a 90-foot, 6-inch diameter pipe to sink through the ship down into the ocean depths.
The ship is on its third drill hole, having run into trouble with the first two. But rock and sediment cores brought up from the drills will be used by other scientists to look at the age and changes of this part of the ocean.
"The rocks tell you a lot of what the ocean was like when the sediment was laid down," he said.
Before the ship headed out to open ocean, it lingered north of O'ahu to dig a hole into a prehistoric landslide that took a large chunk of O'ahu into the sea 1 million to 2 million years ago. UH post-doctoral student Sarah Sherman is on board and is working with geology professor Michael Garcia on analyzing the landslide cores.
"They were looking to see if they could actually pick up some of the mud that slipped off the island and actually date it and see when it occurred because no one knows," Duennebier said. "There have been a lot of slides off the island. They were huge. Big enough to cause tremendous tsunamis. These islands are pretty unstable when they're building, with very steep sides."
Geology professor Moore says the landslide off O'ahu was catastrophic, slicing 100 miles off the windward side along a 100-mile coastline of the Ko'olaus.
"There are big pieces of O'ahu sitting more than 50 miles out on the sea floor," said Moore. "It was one of the largest that happened on earth, and it happened very quickly and probably generated a huge tsunami, say 50-100 feet high when it hit California. At least 25 percent of the island fell off."
It is a process that has happened repeatedly off the flanks of all of the volcanoes on the islands, Moore said.
"We see evidence of similar landslides that have occurred on Mauna Loa," he said, "and right now, the entire south flank of Kilauea is slowly moving, about a meter every 10 years."
Scientists think one such landslide generated a tsunami so big it washed over the "saddle" of Maui, to help create the landscape of today.
This is part of the process that actively changes the Islands, but scientists haven't yet been able to date when the North O'ahu landslide occurred.
"Did it happen during the main building of the volcano? While it was still undersea? Or after it came to the surface?" Moore said. "If we can figure out the timing, then we have a better chance to figure out the actual cause and make predictions."
Reach Beverly Creamer at bcreamer@honoluluadvertiser.com or 525-8013.
