Electrokinetic phenomena associated with a water injection experiment at the Nojima fault on Awaji Island, Japan

Self-potential variations were measured to estimate the magnitude of electr okinetic and hydrological parameters (zeta potential and permeability) of t he Nojima Fault zone in Awaji, Japan. The study observed self-potential var iations that seemed to be associated with water flow from the injection wel l to the fracture zone, which were induced by turning the injection on and off. Amplitudes of the variations were a few to 0.03 V across 320-450 m dip oles. These variations can be explained well with an electrokinetic model. The quantity k/zeta (permeability/zeta potential) is in the range 1.6 x 10( -13) - 5.4 x 10(-13) m(2)/V. Permeability of the Nojima fault zone can be e stimated as approximately 10(-16)-10(-15) m(2) on the assumption that the z eta potential is in the range -0.01 to -0.001 V.