According to new research, the web of submarine cables that transmit data around the world could one day be used to detect earthquakes and tsunamis. During a test run last year, one of Google’s fiber optic cables was able to successfully record earthquakes in the area by detecting distortion in the light pulses sent along the cable. This is a new approach to an idea that researchers have been working on for the past few years.
‘Can we find a cheaper way to cover the ocean with geophysical sensors? There is already this infrastructure for telecommunication cables. If you can turn it into sensors, it’s great – and that’s what we’re doing now, ‘said Zhongwen Zhan, an assistant professor of geophysics at the California Institute of Technology and lead author of the research published in the journal today. . Science.
Aside from the important task of sending data around the world, these cables could one day send early warnings to people ashore if a tsunami goes their way. They can also take a closer look at seismologists and geophysicists earthquakes that occur underwater. Since almost all of the sensors currently used to detect earthquakes are on land, these cables can fill large gaps in scientists’ ability to detect seismic activity. The new approach does not even require the installation of new equipment on the existing web of more than a million kilometers of fiber optic cables cutting across the seabed.
The new approach uses the cables already designed to do. When a transmitter on one side of the cable sends a light signal that emits data, light waves are directed in a certain direction. When an earthquake strikes, it can shake, bend or twist the cable – and it changes the orientation of the light waves. On the other side of the cable, Google notices and corrects distortions. Now he wants to share his data, changes to the so-called “polarization state” of light, with seismologists like Zhan so they can study the earthquakes that caused the distortion.
Between December 2019 and September 2020, Zhan’s research team documented about 20 moderate to large earthquakes using Google’s 10,500 kilometer cable, Curie, which runs from Los Angeles, California to Valparaíso, Chile. The cable could also pick up swells in the ocean caused by storms. This suggests that the technique could also be used to detect tsunamis, which could cause earthquakes.
The ability to see tsunamis while still far from the beach can save lives. In addition to a better view of the ocean than the small number of existing sensors specifically designed to search for tsunamis, fiber optic cables can also send much faster warnings to the shore, according to Google – perhaps in a matter of milliseconds.
“We are humbled and excited about the possibility of working with the optical, underwater and seismic research communities to use all of our cable infrastructure for greater societal benefits,” Google wrote in a blog post last year, shortly after the company went to Zhan to further develop the new approach to seismic observation on the seabed.
“We hope this new approach can really give people a better chance of capturing these events early, so that people have more time to respond,” says Zhan.
In 2018, similar research was published which showed that seabed cables have the potential to detect earthquakes and tsunamis – but the approach comes with some limitations. Cables had to be equipped with specialized equipment to shoot lasers into the cable. By comparison, this new approach saves money because it does not require any new infrastructure. There were also concerns that the addition of equipment to the cables could open the door to security breaches, enabling bad actors to gain access to data sent through the network. Zhan says this is not a problem with the new approach; scientists cannot see information about the transmitted content when they study the polarization of light.
“It’s a perfectly safe way to leverage existing infrastructure to do something that’s good for society and science,” Zhan said.