Scaled Layer Model

Theoretic studies show that there are two kinds of seismoelectric signals that can be induced with acoustic waves. First are electric and magnetic fields induced by the propagation of a seismic wave in a homogeneous porous medium; second are EM waves generated at an interface or through a heterogeneous medium. The seismoelectric signal induced inside the porous medium is a localized and stationary electric signal. When an acoustic wave propagates across an interface, a radiating electromagnetic (EM) wave can be generated due to the different properties of the interface media. A layered model is built with Lucite block and epoxy-glued sand. Five sets of electrodes are buried in the glued sand to measure the electric signals in the sand generated by a plan acoustic transducer. Experiments show the seismoelectric EM wave can be induced by a seismic wave at an interface and received by an electrode at the different location. When an acoustic wave propagates inside a porous medium, it induces a localized and stationary electric field. The induced electric signal can be recorded only at the area where the acoustic wave arrives. It does not propagate in the porous medium. Its apparent velocity is the acoustic wave velocity.