Fracture mechanics of snow avalanches - art. no. 011305

Dense snow avalanches are analyzed by modeling the snow slab as an elastic and brittle plate, attached by static friction to the underlying ground. Th e grade of heterogeneity in the local fracture (slip) thresholds, and the r atio of the average substrate slip threshold to the average slab fracture t hreshold, are the decisive parameters for avalanche dynamics. For a strong pack of snow there appears a stable precursor of local slips when the frict ional contacts are weakened (equivalent to rising temperature), which event ually trigger a catastrophic crack growth that suddenly releases the entire slab. In the opposite limit of very high slip thresholds, the slab simply melts when the temperature is increased. In the intermediate regime, and fo r a homogeneous slab, the model display features typical of real snow avala nches. The model also suggests an explanation to why avalanches are impossi ble to forecast reliably based on precursor observations. This explanation may as well be applicable to other catastrophic rupture phenomena such as e arthquakes.