Physics: Slab avalanche origin similar to that of earthquakes

Snow slab avalanches arise due to fracturing processes that are similar to those that occur in strike-slip earthquakes — in which landmasses move almost horizontally with respect to each other —according to a study published in Nature Physics. This finding may help to evaluate the potential size of avalanches, which may improve hazard mapping and forecasting procedures in mountainous regions.

A slab avalanche — one of several types of avalanche — occurs when a porous, weak layer of snow lies on a mountain slope, buried under a more cohesive slab of snow. When cracks form and spread in the porous layer, the whole snowpack is pulled down the slope.

Johan Gaume and colleagues modelled the development of cracks that lead to slab avalanches. The authors reveal that the propagation speed of cracks can be extremely fast — more than 360 kilometres per hour — making it almost impossible for a skier or snowboarder to escape the release zone of a large avalanche. The findings were experimentally validated by analyzing video recordings of an actual, full-scale avalanche in the French–Swiss Alps triggered accidentally by the jump of a professional snowboarder.

The results suggest that a relatively simple and time-efficient computational model could be used to evaluate avalanche release size for risk management procedures. Given the analogies revealed between avalanches and so-called strike-slip earthquakes, the authors additionally expect that future large-scale avalanche release experiments may also lead to valuable insights for earthquake scientists.