Hydroelectric coupling in a Clayey Material

The hydroelectric coupling generating self-potential anomalies recorded on the Earth's surface has received a considerable attention in the last four years. Geophysical applications include the use of this phenomenon for mapp ing subsurface fluid flow, the study of hydrothermal activity, and the use of self-potential anomalies to monitor volcanic activity and the possibilit y, still debated, of seismic activity forecasting through the use of electr omagnetic precursors of electrokinetic nature. We model here two key-parame ters relevant of the hydroelectric coupling in clayey porous rocks. These t wo parameters are the zeta -potential and the specific surface conductivity , which depend on the electrochemistry of the pore water/mineral interface. They are modeled in the case of a kaolinite saturated by a NaCl brine usin g a triple layer model (TLM) in which the parameters are optimized using th e Simplex algorithm.