AAAS: “Seafloor telecom cable transformed into giant earthquake detector.” Since seismic listening posts are sparse on the vast + remote ocean floor, ‘researchers can’t detect the first shakings of tsunami-causing earthquakes or the seismic waves that penetrate Earth’s deep interior like x-rays, carrying information that illuminates structures in the mantle and core.’ Serendipity to the rescue: “the abyss is home to another kind of technology: the fiber-optic cables that shuttle internet data around the world.” Earthquakes minutely shift the course of photons racing through the fibers.
“Now, a team led by researchers at Nokia Bell Labs has advanced that technique to its ultimate realization, turning a 4400-kilometer telecom cable linking Hawaii to California into the equivalent of 44,000 seismic stations, spaced 100 meters apart.” The proof was in the pudding: “During testing earlier this year the Pacific Ocean cable picked up both the signal of a magnitude 8.8 earthquake that struck the Kamchatka Peninsula in late July and the faint signature of an ensuing tsunami wave as it passed through the ocean and subtly deformed the sea floor.” The new technique builds off methods ‘developed by Giuseppe Marra, a metrologist at the United Kingdom’s National Physical Laboratory, who earlier this decade devised a way for laser pulses to coexist with internet traffic.’ The method depends on a fiber-optic technique called “distributed acoustic sensing” (DAS), which scientists have used on land to detect the rumblings of volcanoes + glaciers, and even the footfalls of college marching bands. “The beauty of this tech is that it can run on legacy cables,” says Martin Karrenbach, a co-author and geoscientist at Seismics Unusual.
But the military might object because the fiber sensors could pick up submarine traffic. Telecom companies might hesitate to tell scientists exactly where their cables are for security reasons. “Those logistical and political problems may be bigger than the technological.” Need to ponder this for a moment.
