Undersea Internet Cables Can Detect Earthquakes and May Soon Warn of Tsunamis

“It’s always been the case that cables get laid first and then people start trying to think of new ways to use them,” wrote science fiction novelist Neal Stephenson in Wired in 1996. “Once a cable is in place, it tends to be treated not as a technological artifact, but almost as if it were a natural mineral formation that could be mined in a variety of ways. “

Each cable is about the thickness of a garden hose, but it’s mostly a protective sheath around a dozen thin strands of glass, which are so pure as a block of a mile thick would appear as clear as a freshly washed windshield. Today, about three hundred cables carry ninety-nine percent of transoceanic data traffic.

Bruce Howe, an oceanographer at the University of Hawaii, has been adding scientific instruments to undersea cables since the early 1990s. Telecommunications companies lay new cables about every quarter century to anticipate disturbances and incorporate materials more advanced. “Whenever a company decides to turn off their cable system, instead of abandoning it in place like it was back then, we thought science could use it,” I said. he said.

At the end of the years, Howe led the installation of part of the ALOHA Cabled Observatory, built on an old AT&T cable located one hundred miles north of Oahu. He and his colleagues later wrote that the team struggled to connect their instruments to the cable and that the installation struggled to reach its full potential, in part due to “still all-too-common cable and connector problems “.

Similar attempts to co-opt mothballed cables have also stumbled. In 1998, scientists added a seismometer, hydrophone, two pressure gauges and other instruments to an outdated cable that linked Hawaii and California, but the system failed after just five years. One system near Hawaii developed a short six months after deployment, and another was damaged by fishing activities off the coast of Japan. Commercial second-hand items were not the way to go.

Howe began to wonder if it was possible to integrate scientific equipment into working telecommunications cables, which are meticulously maintained by the companies that profit from them. He and his colleagues designed temperature, pressure and seismology probes that would fit neatly into cable repeaters. “The telecommunications people were adamant that they wanted nothing to do with us,” Howe told me. As he recounted the story, they replied, “No way, as it would affect telecom reliability.” This response disappointed scientists, who later estimated that piggybacking on hard-wired infrastructure would give researchers data at one-tenth the cost of building their own system from scratch.

Installing a transatlantic cable takes two to three years and about two hundred million dollars, according to Nigel Bayliff, CEO of cable company Aqua Comms. A single repair can cost two million dollars. Any change to a working system, even a modest science package added at no cost to the cable company, could become a liability. “It’s kind of like asking for a different toilet on the space station,” Bayliff told me. “It’s, like, ‘Really, guys? Do you really want to risk the whole space station to change the toilet?

“The only business reason these cables exist, as far as we’re concerned, is for data connectivity,” said Bikash Koley, vice president of global networks at Google, who laid long stretches of cables in partnership with telecommunications operators. said. The company has no plans to add instruments to its cables, he said.

There are also legal obstacles. Because seabed telecommunications cables are treated as an essential public service, they are granted certain freedoms under the United Nations Convention on the Law of the Sea, but the nebulous category of “marine scientific research” is only granted. not necessarily the same privileges. Bayliff worries about what might happen to telecommunications projects if they contribute to science.

“Is ninety percent telecom, ten percent science a science cable now?” Bayliff asked. We may not know until a first cast member tests the legal waters. But he added that governments may be able to solve this problem by mandating collaboration between companies and researchers. “Once it becomes the norm, it will happen all the time and no one will worry because the risks will all be the same for everyone,” he said.

Howe and his team eventually worked with the government of Portugal, which was planning to replace its aging cable system and knows a thing or two about earthquakes at sea. In 1755, a massive earthquake southwest of Lisbon caused a tsunami and devastated the capital. Tens of thousands of people died.

“They’re motivated,” Howe told me. “They see this not only in terms of the operational costs of telecommunications, but also in terms of the human costs, and governments may need to really balance those kinds of considerations. Companies won’t do that. The Portuguese government has approved the project and Howe expects the appropriation of at least one hundred and twenty million euros to occur later this year. The cable will connect Lisbon, the Azores and the island of Madeira; once it is operational in 2025, the motion, pressure and temperature sensors in the cable’s repeaters will serve as a seabed science platform and tsunami warning system.

For scientists to break the deadlock with the cable industry, they needed ways to use the data that already exists, without modifying submarine cables or repeaters. Marra’s chance discovery proved that it was possible.

Then, in 2020, Google agreed to share light polarization measurements from its fiber optic network with a science team that included Zhan and other researchers from Caltech and the University of L’Aquila, Italy. Koley told me Google scientists were happy to collaborate, as long as they didn’t need to add instruments to their cables. “This was a data set that you would have actually thrown away otherwise,” Koley said. “It doesn’t do us any good.”

The researchers identified the polarization changes that occur as cables bend, twist and stretch, and cross-referenced the changes with dozens of earthquakes that seismometers detected over a nine-month period. This approach is not as sensitive as the Marra or DAS method, but it does not require sophisticated technology in the form of an advanced laser. “Because the method is so easy to implement, we actually have six or seven cables on board, providing data,” Zhan said.

Last year, Google gave Marra and his team access to a cable landing station in Southport, England, where the company used a cable that stretches to Dublin and then to Dublin. in Halifax, Canada. The company was willing to give researchers temporary access to certain channels when it was not using them. The researchers drove five hours from their lab in Teddington and installed custom lasers and detectors, as well as computers they could access remotely. They now had the power to detect phase shifts under the Irish Sea and the Atlantic Ocean.

But they still needed a way to determine where the phase changes were occurring in order to determine the exact location of the seabed movements. To solve this problem, the researchers took advantage of tiny mirrors built into fiber optic repeaters, which normally help technicians diagnose problems on specific stretches of cable. The one hundred and twenty-eight mirrors between Southport and Halifax allowed them to identify the specific part of the cable where a phase shift first occurred. Their approach had the potential to turn the cable into one hundred and twenty-nine localized earthquake detectors.

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