Tracking avalanche nucleation in situ – A real-world experiment with embedded fibre optics

Alpine mass movements pose a considerable risk to people and infrastructure. Snow avalanches pose a particularly prominent risk due to their widespread occurrence and potential catastrophic consequences. While significant advances have been made over the last decades to forecast avalanches, the spatio-temporal conditions that lead to avalanche release remain elusive. In fact, the problem of avalanche release is comparable to earthquake nucleation: An earthquake rupture and the fracture of a snow slab avalanche share the same underlying physics. As in the case of earthquakes, the observation of the rupture process of avalanches is limited to sensors in the farfield, such as seismic and infrasound arrays, and optical and radar methods, as well as laboratory experiments. While laboratory observations, far-field measurements on experimental test sites, and numerical simulations allow us to paint an ever more precise picture of the physics of avalanche nucleation, in situ measurements of crack propagation in the near-field of a real-world avalanche remain inaccessible so far.

How to perform such a measurement, which would not only allow us to understand the underlying physics better, but also might open new pathways to measuring precursory processes?

We designed a field experiment tackling the in situ observation of crack propagation and precursory processes. Leveraging a dense grid of seismic sensors we aim to capture the deformation in the nearfield prior, during, and after avalanche nucleation with Distributed Acoustic Sensing (DAS). In total, more than 3 km of fibreoptic cable were pulled from the top into the the steep slopes of Brämabuel near Davos (Switzerland) in autumn 2025. The cables were installed prior and during the first significant snowfall of the season, on known avalanche release slopes. Hence, they are placed centimeters below the expected weak layers, thus effectively making them an embedded strain sensor in a real-world experiment. To increase the probability of capturing the nucleation process, our DAS interrogator continuously samples at 2 m and 200 Hz, with the possibility to increase sampling rates to 1000 Hz for periods of increased avalanche risk. This continuous high spatio-temporal sampling will allow us to differentiate naturally and human-triggered slabs; in fact, skiers are easily identified in the data. In this talk, we will report on the first measurements of the 2025/2026 season and highlight the monitoring potential of our installation;