How pore fluid pressurization influences crack tip processes during dynamic rupture

[1] We calculate temperature and pore pressure rises along a steadily propagating shear crack, assuming a given shear stress profile along the crack (i.e., initially neglecting effects of pore pressure on shear stress). In the limit of a singular crack, temperature and pore pressure rises are a step function in time. We verify that pore pressure can indeed be neglected at the tip and in the cohesive zone of the crack in the case of strong velocity weakening of the friction coefficient (e.g., as governed by flash heating of asperities, like analyzed in a recent numerical simulation of spontaneous rupture). In such cases, the local fracture energy needed to increase the crack length is thus likely to be governed by "dry" frictional processes with effective slip weakening distance of the order of 20 μm, while thermal pressurization may affect the later stages of slip and hence the overall fracture energy attributed to the propagating rupture.