Science / Medicine : Ocean Cables Called On for New Role : Seismology: Outdated trans-Pacific telephone lines will be donated to scientists. They will be used to monitor earthquakes and conduct other research.

Scientists who have been frustrated for decades by their inability to place permanent seismic and oceanographic monitoring stations on the ocean floor are on the brink of realizing their dream by using transoceanic telephone cables that have outlived their original purpose.

On Thursday, AT&T; and its Japanese counterpart, Kokusai Denshin Denwa Ltd., will donate part of the first cable system to span the Pacific to two scientific organizations that plan to use it to supply electricity and a communications link to ocean-floor systems in the western Pacific.

The vital link, which has been replaced by a fiber optics system, will allow scientists for the first time to install permanent seismic monitoring stations on the ocean floor between Guam and Japan. Eventually, scientists hope to extend the program as other cables become available.

“There’s a great deal of excitement” over the potential of the program, said Rhett Butler, a seismologist with the Incorporated Research Institute for Seismology (IRIS) of Arlington, Va., one of the organizations that will receive title to part of the trans-Pacific cable next month. The institute, which coordinates seismic research for 70 U.S. colleges and universities, will be joined in the program by the Earthquake Research Institute of the University of Tokyo.

“It’s a tremendous opportunity for scientists,” said Alan Chave, an oceanographer with AT&T;’s Bell Laboratories. The cost of laying cable across the oceans is so great that “we could never possibly do it” for scientific purposes alone, he said, but since the cables are there already they provide a chance to create a true global network of monitoring stations at a bargain-basement price.

For the first time, scientists will be able to study offshore seismic activity on a continuing basis, including movement along faults, changes in the contour of the ocean floor that could indicate an imminent quake, and electromagnetic emissions from the Earth before and during quakes. The program could also aid research in a number of other areas that are global in scope.

Oceanographic applications hold great promise for such areas as global changes in the oceanic environment, a matter of concern to scientists who fear that the planet may be warming because of the greenhouse effect.

The only way to find out if that is true, Chave said, is to monitor the entire planet simultaneously, and collect data continuously over a period of many years. One crucial tool in that effort could be the cables that are being abandoned around the world.

The program is so new that no price tag has been set yet, but scientists believe they have come across a resource that is so valuable it cannot be wasted.

“This will give the cables another life after retiring from telephone use,” said Butler.

In most cases the cables are in extremely good shape, although the link between California and Hawaii was somehow severed off the coast of California about a year ago. That cable could still be usable from Hawaii to the point where it is broken near the California coast, and it could eventually be reconnected to the mainland if that proved worthwhile.

Except for that problem, the trans-Pacific cable “is just about as good as it was when it was first put down in the early 1960s,” said Bell’s Chave. The cable should be useful for “at least another 20 years,” he added.

Chave said the cable can provide three things for science: a line to transmit power to ocean-floor instruments; a communications link to extract data immediately from those stations; and an ability to operate a wide range of instruments remotely.

“We can’t do any of those (without the cable),” he said.

Historically, scientists were able to put instruments in the sea for up to two years, but the life of the instruments was limited by their batteries and it was not possible to retrieve data as it was collected.

And eventually, “you have to drive a ship out there and pick it up,” Chave said. All of that adds to the cost and reduces the effectiveness, and it creates gaps in the data.

During a “workshop on scientific uses of undersea cables” in Hawaii earlier this year, Junzo Kasahara of the University of Tokyo singled out the primary problem in today’s research when he noted that scientific data is collected “unequally” over the Earth because two-thirds of the planet is covered by oceans and little data is collected there.

“We have estimated the nature of the Earth using these incomplete data,” Kasahara told the workshop.

Retired undersea telephone cables could help fill those gaps by allowing scientists to put permanent facilities on the floors of the oceans and collect data as it is generated. That is particularly important in seismic research, because scientists generally see only the part of the picture that happens on land.

“Right now, there is a huge gap,” said Butler, who has been active in the effort to convert the cables for several years. He noted that there are many seismic stations in California, but “once you leave the coast, the next station is in Hawaii.”

There are still many bugs, including financing, to be worked out, however. Bell’s Chave said the biggest problem is finding a way to install instruments along the cable at a reasonable cost. When AT&T; crews needed to install repeaters, for instance, they did it by cutting the cable, lifting both ends to the surface and splicing their equipment into it.

“That’s half a million dollars a pop,” he said, and that kind of money is hard to come by in scientific circles.

So the program is expected to get off to a slow start and will initially be centered in the seismically active zone between Guam and Japan. U.S. participants hope to build the equipment in Guam that will power the instruments at a cost of “several hundred thousand dollars,” Butler said. The system was designed to transmit power from Guam, not Japan, and it is not reversible, he added.

Japan plans to install three stations on the sea floor. Two of those will be purely for the study of seismic phenomena, such as the propagation of seismic waves along the ocean floor after an earthquake. The third will also include electromagnetic and oceanographic sensors to monitor such things as changes in water temperature and electromagnetic signals emitted by the Earth before and during earthquakes.

Chave said there is also considerable interest in a cable that stretches from Rhode Island to Spain, because that could monitor the Atlantic, including a giant geological structure called the Mid-Atlantic Ridge that bisects the ocean floor and marks the area where the tectonic plates are pulling apart. That cable will become available in 1993.

“There are going to be a lot of opportunities coming up like this in the next 10 years,” Chave said.

The Incorporated Research Institute for Seismology is putting together a proposal for funding from the National Science Foundation. Although the biggest cost of the project has already been paid by the companies that installed the cables, it will not be cheap to build sophisticated ocean-floor systems and install them.

Chave said several cost-cutting concepts are being studied, including the installation of “junction boxes” along the cables. That would require a one-time splicing into the cable for each box, and instruments could be added at any time by simply “plugging them in.”

And ways will have to be found to attach the instruments firmly to the ocean floor so that such things as seismometers will not be confused by currents and shifts in the mud at the bottom of the sea.

The program is so new that there is no consensus on how those objectives would best be met. But U.S. scientists believe they will be able to learn much at bargain basement prices in the initial effort, because the government of Japan plans to spend $10 million on the three ocean-floor stations, far more than the U.S. obligation.

Since the power to run the cable between Guam and Japan must originate in Guam, it will be up to American scientists to provide that at a cost far less than the Japanese investment in the program. In exchange, U.S. scientists will share fully in the research and results from the Japanese stations.

“This is an instance where we can learn a great deal about working with cables for very little money,” said Chave. “The Japanese are budgeting $10 million. If we can learn whether this is worth doing (for the cost of providing the facilities in Guam), then it’s a good deal.”

SEISMIC RESEARCH NETWORK

Telephone cables that span much of the world’s oceans will become available for other uses within this decade, and scientists hope to see at least some of them to run seismic and oceanographic instruments on the ocean floor.

This map shows cables that are expected to be replaced by fiber optics systems by the end of this century. Part of a cable that links the United States and Japan will be turned over to research organizations on Nov. 1. That cable runs from Guam to Japan, and scientists plan to use it to supply power and extract data from three subsea stations along that route.

Source: AT&T;