Fig. 6.

Normalized crack speed along the PST column for different slope angles ($\psi$). The blue line shows the crack speed evolution for a PST in flat terrain ($\psi$= 0°), the orange line that for a tilted PST ($\psi$= 35°). The dashed light blue lines correspond to the tilted PSTs with slope angles between 5 and 25°; the dashed light orange lines correspond to tilted PSTs with slope angle 45°. The blue background corresponds to the range of sub-Rayleigh crack speed ($c_{\mathit{wl}}<c_s^{\mathit{slab}}$), the yellow background to the range of supershear crack speed ($c_{\text{wl}}>c_{\text{s}}^{\mathit{slab}}$). The yellow line represents 1.6 $c_{\text{s}}^{\mathit{slab}}$