| dc.description.abstract | Rock deformation experiments are utilized to investigate the frictional behaviors and the associated mechanism of a fault during earthquake nucleation and ruptures. In particular, rotary shear apparatuses, characterizing with the deformation of large displacement and high velocities, are allowed to determine the fault behavior and its mechanism operated during earthquake propagation. In general, incohesive materials (fault gouges) are the dominant component within a fault core. Therefore, the studying materials, including both natural and synthetic gouges, are widely utilized with rotary shear apparatuses. So far, experiments on gouges deformed at seismic rates are confined with Teflon rings and at low normal stresses (0.5 to 3 MPa), sometimes with the issues of gouge extrusion and chemical contamination. Here we develop a metal pressure vessel which allows to deform gouges at high normal stresses (up to 18 MPa) and at seismic rates and, importantly, without gouge and/or fluid extrusion. The results show (1) the resistance of the pressure vessel (metal-to-metal contact) is extremely low (friction coefficient≈0.02) and (2) similarity to the previously published data, suggesting the data of the pressure vessel is convincing. In particular, deformed at seismic rates, significantly different frictional behaviors of kaolinite between room humidity and water-saturated conditions are observed (small fracture and short dynamic weakening distance is observed under room humidity condition, and the opposite is observed under water-saturated condition). It suggests that under room humidity flash heating can rapidly increase temperature and facilitate frictional melting (thermal decomposition) on gouges to promptly reach steady state of friction. Instead, under water-saturated condition, because water can absorb frictional heat and be incompressible, flash heating is inhibited, displaying a large fracture energy and large dynamic weakening distance. The dynamic weakening is still unclear (fluid pressurization, thermal pressurization, or elastohydrodynamic lubrication) and further experiments are required for the determination. In summary, the designed pressure vessel could expand the experimental conditions and allows to enrich the understanding of fault (landslide) deformation. | en_US |