Avalanches may be caused by earthquake-like shifts in snow

Avalanches may happen when layers of snow crack and slide in a way similar to a type of earthquake. The computer simulation that uncovered this connection could lead to more precise methods of avalanche forecasting.

Most avalanche-related fatalities happen from “slab avalanches”, which begin with a slab of snow sliding down a mountain. This is set off by the snow fracturing at speeds of more than 300 kilometres per hour. However, exactly how this speed is reached was unclear.

Johan Gaume at the Swiss Federal Institute of Technology in Lausanne and his colleagues have now run hundreds of day-long computer simulations that modelled large volumes of snow to uncover how these fast fractures come about.

The team found that in the build-up to an avalanche, a layer of weak, porous snow collapses underneath a harder slab. This causes the harder slab to begin sliding down the mountain. Initially, it fractures and moves slowly. But after sliding 3 to 5 metres, the downhill pull of gravity induces tension forces within the slab, which make it crack and slide much faster.

To confirm that these results were realistic, the team analysed a video of an avalanche accidentally triggered by professional snowboarder Mat Schaer, a former student of Gaume’s. This analysis showed the snow fractured and moved just as it did in the simulations.

Similar fast fracturing can also be seen in earthquakes where two fault planes slide laterally against each other.

Huihui Weng at Nanjing University in China says that the connection between avalanches and earthquakes is exciting because it means that seismologists like himself could learn more about earthquakes by observing avalanches. “This work can improve our understanding of both,” he says.

The new work could also help predict the size and destructive potential of avalanches, says Gaume. His team wants to use the current work to develop quicker simulations that could be run on personal computers. These would allow researchers to classify many areas of the Alps based on the kinds of avalanches that could happen there. The information would be useful for skiers and it could help guide zoning practices to ensure that houses aren’t built in areas where particularly destructive avalanches are probable, he says.

Journal reference: Nature Physics, DOI: 10.1038/s41567-022-01662-4