Telecom Fiber-Optic Cables Measured an Earthquake in Incredible Detail
The same optical fibers that accompany global Internet traffic now listen to the pulse of the planet, capturing earthquakes in greater detail than traditional seismic networks.
In a recent Science study, researchers used 15 kilometers of telecommunications fiber near Mendocino, California, to record the region’s largest earthquake in five years, capturing in detail how the magnitude 7 rupture began, slowed down and sped up, accelerating even faster than the speed of sound.
“It’s almost like you look at Saturn and say, ‘That’s a star.’ Then you’re given a new telescope and you suddenly realize, “Oh, my God, there’s actually a ring around it!” “, says Zhongwen Zhan, a geophysicist at the California Institute of Technology, who was not involved in the study.
On supporting science journalism
If you enjoy this article, please consider supporting our award-winning journalism by subscription. By purchasing a subscription, you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.
Fiber optics, one of the most remarkable inventions of modern science, are designed to transmit light, which can carry coded information with extreme efficiency. Even a small touch or turn can disrupt its flow, which is why telecommunications companies work to minimize environmental interference. “However, for us, what represents noise for telecommunications is data,” explains Zhan.
The oil industry adopted this technology in the 1990s, deploying specialized fiber optic cables to sense temperature, pressure and vibration while drilling. James Atterholt, a seismologist with the US Geological Survey, hoped to adapt these observations to a real earthquake. In May 2022, Atterholt and his team set up a device called an interrogator – “basically a big box with a laser and a computer,” he says – to send beams of light through an unused fiber of a coastal telephone cable. Depending on the vibrations of the ground, tiny imperfections in the fiber reflected light every few meters, transforming the wire into 2,800 mini-seismometers.
On December 5, 2024, when the earthquake struck Cape Mendocino, Atterholt’s team was still monitoring the fiber optic system. His data revealed how the rupture moved east, slowed near a junction where three tectonic plates meet, then accelerated until it reached a “supershear” speed, generating a supersonic boom as it moved faster than the speed of sound. According to the researchers, this is one of the clearest demonstrations of the complexity of a fault leading to supershear rupture. Recording comparable data with the existing seismometer network would require an even more enormous earthquake, essentially right on top of the instruments.
Although the technology has been around for some time, “demonstrating it in a proven case shows that it can improve earthquake early warning systems,” says Brad Lipovsky, a geophysicist at the University of Washington who was not involved in the study. Such a system would be particularly crucial for coastal cities vulnerable to earthquakes and offshore tsunamis. Lipovsky and Zhan also highlight the technology’s usefulness in extreme environments, such as Antarctica, where a specially installed cable could monitor changing terrain and glaciers’ response to climate change.
It’s time to defend science
If you enjoyed this article, I would like to ask for your support. Scientific American has been defending science and industry for 180 years, and we are currently experiencing perhaps the most critical moment in these two centuries of history.
I was a Scientific American subscriber since the age of 12, and it helped shape the way I see the world. SciAm always educates and delights me, and inspires a sense of respect for our vast and magnificent universe. I hope this is the case for you too.
If you subscribe to Scientific Americanyou help ensure our coverage centers on meaningful research and discoveries; that we have the resources to account for decisions that threaten laboratories across the United States; and that we support budding and working scientists at a time when the value of science itself too often goes unrecognized.
In exchange, you receive essential information, captivating podcasts, brilliant infographics, newsletters not to be missed, unmissable videos, stimulating games and the best writings and reports from the scientific world. You can even offer a subscription to someone.
There has never been a more important time for us to stand up and show why science matters. I hope you will support us in this mission.
