Laboratory Measurements of Coseismic Fields: Toward a Validation of Pride's Theory

International audienceAs the seismoelectric interface response has the potential to image subsurface structures with a high resolution, the coseismic part of the seismoelectric field may be perceived as the signature of the relative fluid‐solid motions generated by the propagation of seismic waves. These relative motions were originally described by Biot (1956a, b) and depend on the fluid distribution and pore heterogeneities, giving possibly an access to reservoir characterization. In this chapter, we present the main results of various laboratory studies we have performed in the last decade in order to validate Pride's theory. We discuss how seismoelectric experiments can be designed in order to ensure a quantitative interpretation, and we point out the importance of electrode nature (metallic or unpolarizable), the dipole length, and the conductivity of the fluid. We show that the seismoelectric signal can be easily measured, whereas seismomagnetic measurements need very favorable conditions. The effect of the water saturation is discussed in light of two recent studies showing the role of fluid distribution. When monitoring the full saturation range, we experience a change in polarity of the seismoelectric field that is an original observation of the Biot dynamic compatibility. Eventually, we conclude that Pride's theory is consistent with all our observations: (1) the seismoelectric field is coupled to P waves whereas the seismomagnetic field seems to be associated to S waves; (2) the polarity and the order of magnitude of the seismoelectric field are well recovered, even after a generalization to the partial saturation