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

Abstract Dry-snow slab avalanches release due to crack propagation in a weak snow layer under cohesive slab. Crack speeds can provide insights into the potential size of and inform fracture avalanche models. Despite their importance, slope-scale speed measurements from real are limited. Further, most existing utilize appearance fractures on surface. However, we have no evidence that surface cracking is good indicator tip. Here present novel method estimate movements videos. Our technique uses changes frame pixel intensity, allowing us detect location cracks well before appear We use field experiments numerical simulations validate our applying it five avalanches. estimates show propagate faster up down slope than cross-slope direction; this suggests different regimes likely govern up/down slope, flat terrain.