Fig. 4.

Normalized steady-state crack speed as a function of (a) slab elastic modulus, (b) weak layer elastic modulus and (c) weak layer strength. The dark blue dots correspond to the simulation results. The grey dashed lines correspond to the semi-empirical model (Eq. 3) fitted on data of 110 simulations (R² = 0.96). The blue dotted dashed lines correspond to the results obtained with the analytical model by Heierli [36]. The yellow background indicates snowpack conditions where crack propagation cannot occur; the red background shows snowpack conditions where the weak layer spontaneously fails without any initial crack. The steady-state crack speed is normalized by the slab shear wave speed ($c_{\mathit{wl}}/c_s^{\mathit{slab}}$)