Simultaneous electrical resistivity and elastic wave velocity measurements during triaxial deformation of granite under brine-saturated conditions

We report the first experiments, where simultaneous electrical resistivity and elastic wave velocity measurements are acquired during the triaxial deformation of granite under brine-saturated conditions. Both the resistivity and elastic wave velocity increase slightly during the early stage of deformation owing to crack closure, and then decrease systematically owing to crack development as the sample approaches failure. We observe a complex relationship among the resistivity, elastic wave velocity, and porosity during deformation that is likely attributed to their different sensitivities to crack orientation, tortuosity, and connectivity. The electrical resistivity changes tend to decline as the sample approaches failure owing to the nearly complete crack connectivity, whereas the elastic wave velocities continue to decrease. These characteristic changes in resistivity and velocity at the discrete stages of deformation may provide a clue to understanding structural changes in crystalline basements that are related to crack development and fluid infiltration.

Automated summary

We perform the first experiments to simultaneously measure electrical resistivity and elastic wave velocity during triaxial deformation of granite under brine-saturated conditions. Both resistivity and wave velocity initially increase slightly due to crack closure, then systematically decrease as cracks develop and the sample approaches failure. The relationship between resistivity, velocity, and porosity during deformation is complex and influenced by crack orientation, tortuosity, and connectivity. Understanding these characteristic changes in resistivity and velocity may provide insights into structural changes in crystalline basements related to crack development and fluid infiltration.