Correlation imaging with seismoelectromagnetic waves

In this thesis our goal was to study the possibility of correlation imaging with seismoelectromagnetic waves with laboratory experiments.
A review of the theory of seismic interferometry, its key concepts and historical development is reviewed in chapter 2. Chapter 3 introduces the theory of coupling between seismic and electromagnetic waves and provides a set of governing equations describing the seismoelectromagnetic phenomena. Chapter 4 describes the results of our experiment in which the acoustic Green’s function is retrieved based on cross-correlation between two sensors. It is shown that the sources located in Fresnel zones around stationary phase points contribute coherently to the retrieval of the Green’s function. The Green’s function is retrieved from the stationary phase contribution of the integration over all sources. Sources which are located far from the stationary phase points give an oscillatory contribution that cancels to zero.
In order to employ seismoelectromagnetic waves for interferometry, it was first needed to detect the converted seismoelectromagnetic signal. Experimental results about measurements of the seismoelectric signal are presented in chapter 5. The interface response is measured for natural Bentheimer sandstone saturated with sodium chloride solution. Measured seismoelectric signals are compared with wave propagation model predictions based on the electrokinetic theory. Chapter 6 presents experimental results about correlation imaging with acoustic and electromagnetic waves. By applying interferometry to wave fields generated from a distribution of sources, the electric response of a sensor to a virtual pressure source is reconstructed. In this chapter we report two laboratory experiments of correlation imaging with seismoelectromagnetic waves. In the first experiment source position is on a circular arc around the receivers. In the second experiment, the source is translated along a line which is parallel to the sandstone surface. This configuration is more similar to the geometry of sources in actual field experiments, where sources are located on the ground surface.