How Deep Sea Cables Could ‘Transform’ Earthquake Detection


Laying of a submarine cable in Spain, one of the more than 600,000 kilometers of fiber optic submarine cables.

Laying of a submarine cable in Spain, one of the more than 600,000 kilometers of fiber optic submarine cables.
Photo: ANDER GILLENEA / AFP via Getty Images (fake images)

Many miles from the western shore of the Americas, a submarine cable connects Los Angeles, California with Valparaíso, Chile. Stretched from end to end, it is equal to four fifths the diameter of the Earth. The cable is fiber optic; it is a lifesaver for data transmitted between the two continents. But according to new research, the cable could easily do double duty: mitigate the disastrous impacts of earthquakes and tsunamis.

The results come from an interdisciplinary collaboration between geophysicists and network engineers who observed the alterations in the polarization of the light that is transmitted through the cables. A patent has been filed for the equipment article on the subject, published On Wednesday in the journal Science.

“There are scientific and social implications here,” said Zhongwen Zhan, lead author of the new paper and geophysicist from California Institute of Technology, in a video call. “Most of our geophysical sensors to detect earthquakes and study what the interior of the Earth looks like are on land, but many of the most important geological processes are occurring in the ocean. We take advantage of pre-existing cables in the ocean for a relatively scalable way to detect earthquakes. We believe that in the future we can use them for early warnings of earthquakes and tsunamis ”.

In the unforgiving online world we live in, where movies shot a century ago can be streamed at the touch of a button and you can talk face-to-face with someone on the other side of the planet, fiber optic cables bear the brunt of that. informative load. Submarine cables like Google’s “Curie” cable constantly transmit large amounts of data at breakneck speeds to keep the world connected.

Unavoidable imperfections in cables mean that the polarization of light varies as data travels through them in either direction. Other disturbances, such as temperature fluctuations and human activity, can further affect the polarization of the cables. But deep under the sea, temperatures are relatively constant and humans are rarely present. That means that when a seismic wave ripples through the environment or passes a large rising ocean, it is remarkably detectable in the way it warps the undersea cable.

From seismological research at the bottom of the sea It is time consuming and expensive, reading the fluctuations in polarization of such deep-sea cables is an inexpensive and convenient alternative, the study authors argue. There are many submarine cables to read that data. While the Curie wire is about four-fifths the diameter of the Earth, the total submarine cable network I could go around the planet 20 times. Amid half a century of other geophysical events the team recorded, the Curie Cable detected the 7.1 magnitude earthquake that struck Oaxaca, Mexico, last June.

The research team was able to

The research team was able to “hear” the June 2020 earthquake in Oaxaca, Mexico, in the vibration of the Curie cable.
Photo: PATRICIA CASTELLANOS / AFP via Getty Images (fake images)

When the team first recognized a disturbance in the cable signal and was able to align it with an earthquake, “it was not expected at all,” Zhan said. “No one had ever detected an earthquake by looking at a telecommunications signal itself.”

During the team’s observations, they were able to recognize 20 earthquakes and 30 ocean swells. Importantly, the team cannot yet detect the epicenter of any seismic event (the cables just pick up the disturbance), but Zhan said that, in the future, it might be possible to triangulate the epicenters of earthquakes by observing disturbed polarizations across different cables.

“I think this is going to transform the way we look at the oceans as seismologists,” William Wilcock, a seismologist at the University of Washington who is not affiliated with the new paper, said in a phone call. Wilcock recently wrote a Perspectives in Science article on Zhan’s team’s work. “In my area, there is great concern about the Cascadia offshore subduction zone, and a lot of thought has been put into how to develop offshore infrastructure to improve our monitoring of that. Doing that with dedicated systems costs hundreds of millions of dollars. But being able to use commercial leads to do at least some of that is a huge help to really move forward. “

It remains to be seen whether the method of listening to the Earth is adopted by the telecommunications industry in general. The truth is that this team has shown that we can hear the light, using the by-product of your game. Obligations or send family photos to spy on the seismic activity of the planet, perhaps better preparing ourselves for any small or very, very big will come later.

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