Using video detection of snow surface movements to estimate weak layer crack propagation speeds

Dry-snow slab avalanches release due to crack propagation in a weak snow layer under a cohesive snow slab. Crack propagation speeds can provide insights into the potential size of avalanches and inform fracture and avalanche release models. Despite their importance, slope-scale crack speed measureme...

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Bibliographic Details
Published in:Annals of Glaciology
Main Authors: Ron Simenhois, Karl W. Birkeland, Johan Gaume, Alec van Herwijnen, Bastian Bergfeld, Bertil Trottet, Ethan Greene
Format: Article in Journal/Newspaper
Language:English
Published: Cambridge University Press
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Online Access:https://doi.org/10.1017/aog.2023.36
https://doaj.org/article/7c69bbbe79ad40ae83ddb86ba0da3bec
Description
Summary:Dry-snow slab avalanches release due to crack propagation in a weak snow layer under a cohesive snow slab. Crack propagation speeds can provide insights into the potential size of avalanches and inform fracture and avalanche release models. Despite their importance, slope-scale crack speed measurements from real avalanches are limited. Further, most existing slope-scale measurements utilize the appearance of slab fractures on the snow surface. However, we have no evidence that the appearance of surface cracking is a good indicator of the weak layer crack propagation tip. Here we present a novel method to estimate crack propagation speed from snow surface movements in avalanche videos. Our technique uses changes in frame pixel intensity, allowing us to detect the location of weak layer cracks well before slab fractures appear on the snow surface. We use field experiments and numerical simulations to validate our method before applying it to five avalanches. Our estimates show that cracks propagate faster up and down the slope than in the cross-slope direction; this suggests that different propagation regimes likely govern crack propagation up/down the slope, cross-slope and in flat terrain.