Micromechanics of brittle faulting and cataclastic flow in Mount Etna basalt

Water significantly weakens basalt under stress, with saturation reducing strength by up to 50% compared to dry samples. This finding emerges from 65 uniaxial and triaxial compression experiments on Mount Etna basalt, covering porosities of 5–16% and effective pressures up to 200 MPa. The study reveals that brittle faulting in low-porosity (5%) samples is governed by wing crack propagation under triaxial stress and pore-driven cracking in uniaxial conditions, particularly in more porous rocks. Additionally, shear-enhanced compaction occurs at lower pressures (≥80 MPa) in 8% porosity samples, driven by cataclastic pore collapse—a process consistent with a dual-porosity model. These insights are critical for understanding volcanic system dynamics and have implications for geothermal energy and reservoir management.

Zhu, W., Baud, P., Vinciguerra, S., & Wong, T.-f. (2016). Micromechanics of brittle faulting and cataclastic flow in Mount Etna basalt. Journal of Geophysical Research: Solid Earth, 121(6), 4268–4289. Portico. https://doi.org/10.1002/2016jb012826