Geo-electric observations before 2008 Sichuan Earthquake

摘要

Geo-electric precursors have been observed just before the 2008 Mw 8.0 Sichuan earthquake using a newly developedmeasurement systems and practices. The precursors in geo-resistivity and telluric current has the same period of tidewave (f. g. M2, MSf, etc.) and we call it HRT wave. The shape of the precursor is one directional tidal wave and theamplitude increases days before the earthquake. Through investigation of these precursors demonstrate their correlationwith upcoming earthquakes several days later. Their arrival time is proportional to the distance from the site to theepicentre. One possible explanation of these precursors involves pore fluids disturbances generated in the hypocenterzone. We hypothesize that when the rock stiffness in the hypocenter zone approaches zero, just before an earthquake,pore fluids can be moved to a large distance by tidal forces. This pore fluids disturbance can propagate hundreds ofkilometers in the earth's crust. The period of this disturbance is that of the driving tidal force in the range of 1-5 hours.