The fiber optic cables that we use to surf the internet and call could allow you to provide a landslide or the collapse of a glacier. Research projects carried out in Switzerland are opening up new prospects for monitoring natural risks.
The collapse of the Birch glacier on May 28 in the Lötschental, made the headlines around the world. There is no simple method to predict the exact location of the collapse of a glacier.
![A bundle of optical fibers. [CC BY-SA 3.0 - BigRiz]](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///ywAAAAAAQABAAACAUwAOw== "A bundle of optical fibers. [CC BY-SA 3.0 - BigRiz]")
Satellite images, cameras and radars make it possible to follow their evolution and movement. This technology has notably contributed to anticipating the case of Blatten, but it only provides limited information on activity within the glaciers.
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Scientists in Switzerland and in various mountainous regions such as Alaska think they have found a solution: fiber optic cables that collect micro-vibrations and other pioneering signs of instability. “Optical fiber allows us to detect extremely light seismic events, which other technologies could not measure,” explains Thomas Hudson, seismologist at the Federal Polytechnic School in Zurich (EPFZ), which recently presented the results of his experiences on a Swiss glacier with Seismological Society of America.
Optical fiber to monitor whole glaciers
In 2023, the EPFZ search team installed 1.2 kilometers Optical fiber cables on the Gorner glacierin Switzerland. These cables were connected to a device called “questioning”, which sends laser pulses. This method, known as distributed acoustic detection (DAS), transforms optical fiber into a band of hundreds of seismic sensors. Some of the seismic waves (or ice tremors) come from fractures that form in the glacier. These cracks can compromise the stability of the structure, because they allow the cast iron to infiltrate, which increases the risk of detachment and accelerates the movement of the glacier downstream.
Optical fiber also provides information on the structure and composition of ice. Compared to traditional seismic sensors, which are placed in specific places, cables can be installed more easily on a large surface, explains Fabian Walter, mass movement expert at the Federal Research Institute, Snow and Landscape (WSL). If it was deployed on a larger scale, this technology would monitor entire glaciers, even in difficult to access areas.
Earthquakes, avalanches and debris flows
The detection of seismic activity using optical fiber is not new. DAS technology has long been used in underwater cables to locate ocean earthquakes and volcanic activity. However, it has only been in recent years that its use has been extended to other natural risks and, in this regard, “Switzerland is one of the pioneering countries,” said Fabian Walter. In 2022, this technology was applied for the first time to the detection of avalanches in Switzerland. It also made it possible to measure the small detachments of rocks prior to the Large landslide that occurred near the village of Brienz (GR) in 2023.
What is interesting, observes Fabian Walter is that the fiber optic cables for telecommunications are already present in the basement along the roads, railways and near certain infrastructures. According to him, it would be easy to connect the DAS interrogator at the end of an unused filament or a “black fiber” (an optical fiber cable contains many filaments, but not all are operational).
A technology adapted to developing countries
The current challenge is to develop an algorithm based on artificial intelligence capable of automatically recognizing the relevant signals to distinguish, for example, the movement of a rock from that of an animal. If the system detects a considerable activity likely to cause a landslide or the collapse of a glacier, it can trigger an early alert, giving people time to react before the catastrophe occurs, explains Madhubhashitha Herath, from UVA Wellassa University, Sri Lanka. He is the author of a Study on the use of this technology in monitoring natural risks. The cables are relatively cheap, with low operating and maintenance costs, adds the scientist. “This is why this technology is suitable for industrialized countries as well as in development,” he said.
Thomas Hudson, from EPFZ, thinks that kilometers of fiber optics could be deployed on the most unstable glaciers. “It would be enough to cover the forehead of suspended glaciers, that is to say the part most exposed to the risk of collapse”. However, the system should be calibrated for each site, because “each glacier is unique”, he specifies. And to add: “The fiber optics would complete the range of existing surveillance technologies, such as satellite imagery and radars.” By combining the observations of changes on the surface and in depth, we could improve the monitoring of the most dangerous glaciers “, he concludes.
Luigi Jorio (Swi)/Ain
