Abstract:

With relation to the strength of earthquake fault and its stress release process, the pore pressure within the shear zone is always attracting high attention. The permeability structure of fault zone is of great importance to the understanding of the activating state of fluid, faults strength and stability as well as the coseismic process. The paper introduces the basic principle and methodology of fault permeability research, and summarizes the newest study results in this area. The brittle faults usually have a typical permeability structure, with the lowest value in the core and high values in the damage zone. The fault gouge is the most impermeable and shows high permeability isotropy. In a seismic cycle, the permeability of earthquake fault takes on a characteristic process of abrupt jumping and gradual decreasing. Cementation, fluidrock interaction and solutionprecipitation are the main mechanisms of fault healing. Thermal pressurization is an important and effective dynamic weakening mechanism. When permeability of fault gouge is less than 10-18 m2, earthquake will accompany with a strong thermal pressurization process.

Key words:  fault permeability, thermal pressurization, excess pressure, fault healing, oscillation method