Reviewed by Lexie CornerApr 16 2025
Researchers found that fiber optic cable installed on a Swiss glacier detected seismic signals from crevasses forming in the ice, suggesting the technology’s potential for monitoring icequakes.
Drone view of crevasses on Gornergletscher. Image Credit: Tom Hudson
The stability of glaciers is influenced by crevassing, as these cracks provide a path for meltwater to reach the glacier's rocky base, accelerating both the glacier's movement and melting. However, the harsh environment of crevassed glaciers makes it difficult to deploy conventional seismic equipment to monitor icequakes.
Tom Hudson from ETH Zurich explained that the source of seismic signals in an icequake differs from the shear forces of tectonic earthquakes or the explosive energy of chemical or nuclear detonations. A crevasse is a “crack source, where you have pure opening of a fracture just in one direction,” he explained.
The study is a real-world test case of detecting this opening crack fracture type of seismicity in the subsurface using fiber optics. This is pretty much as close as we can get to a seismic source. Our crevasse quakes are within ten meters of the fiber optic cable, which is quite rare.
Tom Hudson, Senior Research Scientist, ETH Zürich
Hudson’s study demonstrates that fiber optic detection could be effective in monitoring cracks that form in rock, such as in geothermal energy systems or carbon storage reservoirs.
“Because ice is a seismically simpler medium than rock, it’s got a well-known velocity structure and we can really interrogate the source physics. So if we can do that in this simpler environment, then the hope is that maybe we can start to think about doing that in a more complex environment.”
The team deployed a 2D fiber optic grid in the crevasse field of Gornergletscher, Switzerland’s second-largest glacier. Hudson noted that the team was fortunate with the conditions, as they installed the cable during the transition from summer to winter, avoiding the dangers of hidden crevasses under snow.
One of the challenges of using fiber optics for seismic data collection is ensuring the cable is properly coupled with the ground. “It was still warm enough during the day that the fiber would get hot and melt into the glacier a little, because the fiber is black compared to the ice. And then when the fiber melts in, it was cold enough that it froze in place overnight,” Hudson explained.
“So we actually got the best coupling you could probably hope for in terms of the fiber melting and then freezing,” he added.
The researchers detected and located 951 icequakes, identifying seismic waveforms with significant oscillations, or coda, following the arrival of seismic surface waves. While these oscillations can result from water inside crevasses, Hudson and his team suggested that they are more likely due to resonance caused by seismic waves “as they bounce back and forth between the fractures" of multiple crevasses in the crevasse field.”
The researchers also compared the data from the fiber optic grid with data from traditional seismic nodes, finding that fiber optic cables provided nearly 20 times more data than the node array.
“You have some data processing challenges, but you have far more data, and that allows you to basically see the full wavefield in the data itself, which is quite unusual,” Hudson added.
Another advantage of using fiber optics is their sensitivity to a wider range of signal frequencies, including low-frequency signals that can last for hours or even days. This allows seismologists to measure ice flexure over time. Hudson aims to use fiber optics to measure the velocity structure of the ice and create a 3D image of its subsurface.
“I really want to quantify the fracture extent, the fracture density, and see how damaged the ice actually is in this area, so we can see where the icequakes are generated by the fractures. We haven’t yet quantified how many fractures there are and how big they are, so that’s the hope going forward,” he concluded.