Comprehensive Inversion of Magnetic Resonance Sounding – Water Content, Decay Times and Resistivity

Magnetic Resonance Sounding (MRS, or Surface Nuclear Magnetic Resonance – SNMR) is used for direct groundwater exploration and for an improved aquifer characterization. Currently, it is the only geophysical method that is capable to directly determine the free water content and to estimate the pore sizes of the aquifer in the subsurface. However, MRS is basically an electromagnetic method. Therefore, it is sensitive to the resistivity of the subsurface. The water content is the main target of investigation, therefore first inversion routines in the past focussed on the water content. Later on, inversion routines determining water content and decay times became available. Very recently, MRS inversion for water content and resistivity has been realized. We present here a comprehensive inversion of MRS in terms of determining the three inversion parameters water content, decay time and resistivity within one single inversion routine. Within the iterative inversion scheme, the extrapolated initial values are determined on the basis of the physical effective decay times in the subsurface, that are estimated within the inversion scheme.