Aim of the project is the development of an inversion algorithm for magnetic resonance measurements with the incorporation of structural information from ground penetrating radar for improved hydrogeophysical imaging.
In order to characterize the lateral variability of hydrogeophysical parameter, methods such as surface-NMR and ERT are suitable. However, these methods do not allow for imaging sharp boundaries or thin layers and mainly provide only smooth paramter distributions. In contrast, GPR measurements can provide sharp boundaries. Consequently, SIMAR targets to implement the information about sharp boundaries from GPR relections as structural contraint into surface-NMR inversion. The approach has already been sucessfully applied for ERT inversion by including seismic reflections into the mesh generation and lowering the smoothness contrains across these boundaries.
Left: 2D distribution of water content (a,c) and relaxation timeT2* (b,d) derived from MRT smooth inversion using (a,b) and GPR reflectors as structural constraints (c,d). The black lines in (c,d) represent the average GPR reflectors from three GPR-profiles aty=0, +10, +20 m used as sharp boundary constraints in the inversion. The white lines give the reflectors from each GPR-profile used to obtain the averaged boundary. The horizontal dashed black lines are the approximate bounds of the second aquifer and plotted only fororientation, but are not used as constraints.
Right:Sediment log including radar facies interpretation (a), depth profiles of relaxationtimes T2 and T2* (b) and θ(c) at drilling location Eng35B. The figure gives the relaxation time distribution (yellow-red shades), cutoff-time (grey dashed) and hence obtained θ(green crosses) from laboratory NMR, smooth (light blue) and constrained(dark blue) MRT inversion extracted from the 2D model at the location of the drilling and geometric constraints from GPR and water table measurements (black).