Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
4694789 | Tectonophysics | 2007 | 9 Pages |
Abstract
The Nojima Fault Zone Probe was designed to study the properties and healing processes of the Nojima fault, which is the surface fault rupture of the Hyogo-ken Nanbu earthquake (M7.2) of 1995 (1995 Kobe earthquake). In this project, water injection experiments were conducted in a borehole of 1800Â m depth at the Nojima fault. We set up electrodes around the borehole and observed self-potential variations to investigate the magnitude of electrokinetic and hydraulic parameters around the Nojima fault zone. In the 1997 experiment, self-potential variations were in the range of a few to about 20Â mV across 320-450Â m electrode dipoles with hydraulic pressure variations from 3.5 to 4Â MPa. In the 2000 experiment, self-potential variations were in the range of a few to about 85Â mV across 160-260Â m electrode dipoles with the hydraulic pressure variations from 3 to 4.5Â MPa. In the 2003 experiment, self-potential variations were in the range of a few to about 30Â mV across 20-80Â m electrode dipoles with hydraulic pressure of 4Â MPa. These observed self-potential variations were explained well with an electrokinetic effect due to the underground flow of the injected water. From the observed results, we estimated that the ratio of hydraulic parameters (permeability, porosity, and tortuosity) to electrokinetic parameters (zeta potential and dielectric constant) decreased approximately 40% during eight years after the earthquake. This result suggests that the healing process around the fault zone progress.
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Earth-Surface Processes
Authors
Hideki Murakami, Naoto Oshiman, Satoru Yamaguchi, Takeshi Hashimoto, Ryokei Yoshimura,