A new electronic model of seismoelectric measurements: Theory, simulations and experimental validation

Abstract

Seismoelectric (SE) measurements present low voltages signals that are difficult to detect and acquire in a quantitative way. One of the main reasons is the lack of information about the impedance seen by the electronic acquisition system while the SE effect is taking place. Knowing its nature (real or complex) and values are required to better design the electronic acquisition system, to show its limitations and also to better estimate the SE voltage in modulus and phase, i.e. being insensitive to the influence of the electronic acquisition system and contact losses linked to electrode coupling within the medium. There are electronic models that represent the electrodes used to measure these signals but no models representing the whole system output impedance during SE experiments. This is crucial because the model values change depending on many factors such as soil composition. Thus, to give an answer to the remaining questions we propose a novel electronic model of SE measurements which components values are obtained while a SE signal is propagating. We present a new theoretical-experimental method to retrieve the impedance of SE signal sources and better SE signal estimation. To validate the model we performed experiments and simulations. The results obtained present a goodness of fit of 90% between the model and the experimental measurements. They also show that the SE measurements impedance is complex and that even 1 m coaxial cable between the electrodes and the acquisition system affects considerably the SE signal. Hence, to avoid these issues we propose the use of active electrodes that include the preamplifier in the electrode itself.