The Project targets on providing an inversion algorithm structural coupling Magnetic Resonance Tomography and Electrical Resistivity Tomography. This includes the implementation of an efficient calculation of magnetic fields based on arbitrary 2D resistivity distributions.
Water belongs to the natural resources that deserves protection and increasing diverse demand worldwide. Thus, detailed exploration and characterization of aquifers becomes more and more important and hydrogeophysical methods can contribute. Among the available methods, Electrical Resistivity Tomography (ERT) and Surface Nuclear Magnetic Resonance (SNMR) have proven to yield important parameters. A combination of both techniques can provide water content, hydraulic conductivity and salinity.
While 2D ERT is state-of-the-art since 15 years, 2D SNMR or MRT (Magnetic Resonance Tomography) has developed recently. The recent development of multi-channel devices and more efficient loop setups, the time to acquire a full MRT dataset has become more and more acceptable. However, the 2D datasets yield to the question of a suitable inversion algorithm for analyzing the data.
The project COMET not only target to account for arbitrary 2D resistivity distribution but will develop a structurally coupled 2D inversion that is expected to help reducing the uncertainties, as well as to improve the resolution of the inversion result and thus provides valuable input to hydraulic modelling. Consequently, the results of the combined inversion will be 2-D images of the parameters resistivity, water content and relaxation time.
As a first step, a joint inversion for NMR and ERT in the case of 1D was developed.
Next, the forward modeling was extended to permit arbitrary 2D resistivities and caluclate the MRT kernelfunction (Fig. 2).
Finally based on this kernel function, a structurally coupled joint inversion of ERT and MRT was developed (Abb.3).