Researchers at Google Global Networking have found a way to detect undersea earthquakes using technology that already exists in undersea cable networks.
Valey Kamalov and Mattia Cantono reported their findings in a blog post, saying that their findings “could be useful for earthquake and tsunami warning systems around the globe.”
Using optical fibers to detect earthquakes and other seismic events isn’t a new idea, the pair said in their post, but previous techniques were limited to distances of 100 km or less, and required specially designed fibers and sensing equipment.
“We’ve developed a technique that works over tens of thousands of kilometers [and] relies on equipment that is present on the vast majority of the world’s existing fiber optic systems,” they write.
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Google reportedly has the largest submarine cable network in the world, totaling nearly 120,000 km of seafloor fiber optics over 12 different cable systems. “By collaborating with the global subsea cable community, we may be able to improve the world’s ability to detect and research seismic activity around the world,” the blog post said.
How existing fiber optic technology can detect earthquakes
Kamalov and Cantono got their idea from a 2018 paper that described using state of polarization (SOP) change in fiber optic signals to detect seismic events. SOP changes occur due to any sort of mechanical disturbance in fiber optic cables, and software that digitally corrects that distortion is standard at fiber optic endpoints.
By narrowing in on the spectral signatures typical to earthquakes, the pair determined, they could—in theory—detect earthquake signatures anywhere on Google’s undersea cable network.
On Jan. 28, 2020, Kamalov and Cantono detected the earthquake that struck Jamaica, despite Google’s nearest cable being 1,500 km away, and had their observations confirmed by California Institute of Technology geophysics professor Zhongwen Zhan.
A second earthquake originating in the East Pacific Rise, 2,000 km from a Google cable, was detected on March 22, and then on March 28, they detected a quake off the coast of Valparaiso, Chile.
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Zhan’s review of the team’s data found that it was able to detect pressure changes in the ocean, which meant the system could detect tsunamis as well. “This is particularly exciting because today, most tsunami detection equipment is either on shore, or scattered throughout the ocean. The former doesn’t give coastal communities enough time to evacuate, and the latter is limited by the speed of the traveling wave,” the blog said.
Kamalov and Cantono say that their findings are hardly indicative of a finished product, and that much remains to be done. “First, scientists will need to better understand the deluge of complex data that will be generated by monitoring SOP,” they said, which may be a task better suited to machine learning and AI.
They also said that this isn’t a replacement to existing seismic detection systems, but rather “a source of complementary information to enable early warnings for earthquakes and tsunamis.”