The coupled seismoelectric wave propagation in porous media: Theoretical background

Seismic and electromagnetic disturbances are coupled in saturated porous materials through electrokinetic coupling. Two types of seismoelectric signals are generated when a seismic wave propagates through a homogeneous multi-layer porous medium. The first type of the seismoelectric response is generated by a stationary charge separation, in a reference frame moving with the wavefront. This stationary charge separation is analogous to a constant electric dipole and does not radiate electromagnetic waves. The second type of the seismoelectric response is generated when the spherically spreading wavefront impinges on an interface having contrast in mechanical or electrical properties in which a time-varying charge separation is induced. This time-dependent charge separation radiates electromagnetic (EM) energy, which would be detected almost simultaneously across the surface receivers. To enhance the weak signal of the observed seismoelectric signals, processing procedure includes suppressing of the powerline large amplitude harmonic interferences as well as the seismoelectric response type separation. Powerline harmonic interference can be estimated and removed from the data using block or sinusoid subtraction techniques. Discriminating between the first and second type of the seismoelectric EM responses can be done using F-K filtering, because of the distinct near simultaneous arrival characteristic of the interface EM response. Another possible separation technique is a self-deconvolved prediction error filter. This technique is similar to the algorithms that are used for multiple attenuation in reflection seismic data