MERIT – A New Magneto-electrical Resistivity Imaging Technique Part 1: Modeling and Tomographic Reconstruction

A Kemna1, A Tillmann1, A Verweerd2, E Zimmermann2, H Vereecken1

1. Institute of Chemistry and Dynamics of the Geosphere, Forschungszentrum Juelich GmbH, 52425 Juelich, Germany

2. Central Electronics Laboratory, Forschungszentrum Juelich GmbH, 52425 Juelich, Germany a.kemna@fz-juelich.de

ABSTRACT

We propose a new Magneto-Electrical Resistivity Imaging Technique (MERIT), where both electric and magnetic field responses to a variety of low-frequency excitation currents are evaluated to image the resistivity distribution inside an object. Since electric and magnetic field measurements provide partly complementary information, MERIT is expected to yield an improved image resolution compared to conventional Electrical Resistance Tomography (ERT). In this paper we address the magnetic field related modeling and tomographic reconstruction aspects of MERIT. The finite-element method is used to solve both the associated 2.5-D and 3-D forward problems. Laboratory measurements on a physical model, together with corresponding modeling results, exhibit the relatively complex nature of magnetic signatures to be exploited in MERIT even for a simple anomalous body. For first, qualitative imaging purposes, we adapted a simple, sensitivity based Multiplicative Simultaneous Iterative Reconstruction Technique (MSIRT). Application to synthetic data from a phantom yields reasonable imaging results even if only one magnetic field component acts as input to the reconstruction process. The results demonstrate the imaging capability associated with purely magnetic information and are thus promising with a view to the further development of MERIT. Although our ultimate objective is the quantitative imaging of flow and transport processes in undisturbed soils and sediments, the proposed method should be likewise applicable to medical and industrial problems, such as imaging of multi- phase flow in stream pipes.

Keywords Resistivity Imaging, Magnetic Measurements, Electrical Resistance Tomography, Tomographic Reconstruction