MRSmatlab is a manufacturer-independent software tool for processing, modeling, and inversion of surface nuclear magnetic resonance data. Intended as an open platform, MRSmatlab has been growing over the past few years by connecting researchers and making the latest research available to the community. We have developed insights into yet unpublished numerical implementations of signal processing and complex inversion. In addition, we have evaluated a field example demonstrating the need to carefully inspect all the steps of handling surface nuclear magnetic resonance data. MRSmatlab can be obtained by contacting the authors.

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Conventional surface nuclear magnetic resonance (NMR) surveying based on 1D inversions of data recorded using a common (coincidence) transmitter and receiver loop provides only limited or distorted water-concentration information in regions characterized by strong lateral heterogeneity. We introduce a combined field-acquisition and tomographic-inversion strategy suitable for 2D surface NMR investigations of free (i.e., unbound) water stored in hydrogeologically complex regions. Using combinations of coincident and multioffset loops, we take advantage of the range of sensitivities offered by different loop configurations to variations in subsurface free-water concentration. The new tomographic scheme can invert data acquired with diverse loop configurations. Tests of the combined acquisition and inversion strategy on complicated synthetic and observed data demonstrate the substantially higher resolution information provided by combinations of loop configurations vis-à-vis that supplied by a standard coincident loop. A combination of coincident and half-overlapping loop data sets yields tomograms rich in detail, comparable to tomograms derived from a combination of all considered loop configurations. If resources are limited, surface NMR practitioners should consider the half-overlapping loop configuration as an alternative to the standard coincident loop configuration. For a four-station data recording campaign, the half-overlapping loop configuration with 50% more measurements and equal number of loop deployments and retrievals provides significantly higher resolution tomograms than a coincident loop configuration.

Triggered by an extended mathematical formulation of the response signal for magnetic resonance soundings (MRS), which allows the treatment of individual transmitter and receiver loops, we make a comprehensive evaluation and assessment of the emerging new possibilities of the technique. Based on a reformulation of the basic equation, we indicate and interpret the evolving effects. The influence of loop separation on MRS sounding curves in terms of offset and direction is also assessed as is the corresponding sensitivity to depth and lateral spin variation. Interpretation of field data measured with separated loops using the extended formulation is found to fit the predicted response extremely well. From the encouraging results, we derive new aspects of two‐dimensional investigation of groundwater resources. Furthermore, new perspectives of future developments of the MRS technique, with individual loops for optimized field measurements and hydrological applications, are discussed.