Spectral analysis of seismoelectric signal for water saturation monitoring
Résumé
The seismo-electromagnetic method consists of measuring electric and magnetic fields (Bordes et al. 2006, 2008) induced by seismic wave propagation from electrokinetic coupling which are sensitive to the pore fluid properties. Even if the role of water content was studied at low frequencies (electrofiltration), the effect of saturation on seismoelectric is poorly understood. In this study, we performed laboratory experiments in order to monitor seismoelectric signals as a function of water saturation in sand (99% silica). First analysis on direct P waves in time domain seems to show a frequency dependence of the seismic and seismoelectric signal (Sénéchal et al., 2010). In this further discussion, a spectral analysis by Continuous Wavelet Transform (CWT) is proposed to study frequency content variations occuring during imbibition and/or drainage of the sand.