The frictional-slip experiments on pseudotachylytes gouge of Anninghe Fault

Pseudotachylyte was found in graintic gneiss-cataclastic rocks at the western side of Anninghe fault. In this study, we performed frictional experiments of pseudotachylyte gouges under hydrothermal and dry conditions. Velocity-stepping experiments were performed at effective normal stress of 250 MPa, pore fluid pressure of 30 MPa, temperature range of 100 similar to 500 degrees C, and shear velocities between 0. 04, 0. 2 and 1 mu m . s(-1) Experimental results show that at 100 similar to 500 degrees C, the friction coefficient of pseudotachylyte gouges increase with the increasing of temperature, and friction coefficient for dry samples is lower than that of hydrothermal conditions. The slip stability is characterized by velocity strengthening at temperatures of 100 similar to 300 degrees C and velocity weakening at temperatures of 400 similar to 500 degrees C under normal loading rate (1 similar to 0. 2 mu m . s(-1)). The results find that loading rate can also affect the stability of pseudotachylyte gouges. At the temperature range of 100 similar to 300 degrees C, pseduotachylyte exhibits velocity strengthening behavior at experimental standard velocity of 1 similar to 0. 2 mu m . s(-1) and converts to velocity weakening behavior at slow loading rates (0. 2 similar to 0. 04 mu m . s(-1)). Based on the experimental results, it is inferred that the depth of earthquake nucleation is 10 similar to 30 km at the Aninghe fault. Comparing with the frictional experiments of granite gouge, we found that the frictional strength of pseudotachylyte is higher than that of granite, implying that it is impossible for the large earthquake to re-occur at the same location if the last co-seismic rupture was healed by pseudotachylyte. However, it could increase the possibility of unstable slip and nucleation of earthquake, also promote propagation of co-seismic dynamic rupture if there exists pseudotachylyte in fault zone.