Stick-slip mechanics in active fault zones

Hydrous minerals are ubiquitous in fault zones, with a number of these being subjected to dehydration during seismic slip. This reaction has been postulated to have strong effects, controlling both the temperature and pore fluid pressure in the fault zones. This project combines high-velocity and low-velocity shear experiments, performed using a gypsum gouge, at a range of normal stresses covering the brittle-ductile transition to test the controls and feedback within developing permeability in dehydrating minerals. Using numerical simulations to calculate temperature, pore fluid pressure and reaction progress, we infer a wide range of temperatures within the gouge with temperatures varying within the shear zone by over 200 ºC.

The model output, combined with SEM and laboratory data, suggests that fault slip in the presence of dehydrating minerals are likely to generate a very thin shear zone due to the liberated fluid. Depending on the permeability of the comminuted zone this may then trigger slip at lower stresses and delayed in time than without dehydration reactions present.