Permeability Enhancement by Slow Faulting Under High Pore Fluid Pressure

Abstract The morphology of fault zones formed by slow faulting is markedly different from that of brittle faulting. In this study, we quantify the three‐dimensional (3D) pore distribution and permeability structures of two rock samples that have been deformed to failure by slow and brittle faulting, respectively. Our results show that the permeability structure of fault zones varies greatly depending on the faulting mechanism. Fault cores formed by slow faulting exhibit much higher porosity and permeability compared to the surrounding damage zone and wall rocks, unlike those formed through brittle faulting. Since slow slip events associated with high pore fluid pressures are common in active tectonic regions, we propose that slow slip events can serve as a mechanism to maintain the permeable pathways beneath the seismogenic zone, facilitating the movement of mantle‐derived fluids from deep reservoirs toward the surface.