Permeability control on transient slip weakening during gypsum dehydration: Implications for earthquakes in subduction zones

摘要: A conflict has emerged from recent laboratory experiments regarding the question of whether or not dehydration reactions can promote unstable slip in subduction zones leading to earthquakes. Although produce mechanical weakening due pore-fluid pressure increase, this been associated with both stable and slip. Here, new results monitoring strength, permeability, pressure, reaction progress microstructural evolution during are presented identify conditions necessary for instability. Triaxial conducted using gypsum a direct shear sample assembly constant normal stress that allows measurement permeability sliding. Tests temperature ramp 70 150 °C different effective confining pressures (50, 100 MPa) velocities (0.1 0.4 μm s−1). Results show bassanite induces transient stable-slip is controlled by evolution. At onset dehydration, low promoted pore compaction build-up weakening. The increase content shows clear evidence related development R1 Riedel shears P foliation planes where preferentially localized along these structures. continued production bassanite, which stronger than gypsum, provides supporting framework newly formed pores, thus resulting drop fault strength increase. After reaction, deformation characterized on fully dehydrated product, transition velocity-strengthening velocity-weakening behaviour at above ∼140 localization narrow Y-shear planes. This study highlights generic required trigger instabilities reactions. It reacting phase earthquake triggering.