A comprehensive study of parameter determination in a joint MRS and TEM data analysis scheme

Abstract

ABSTRACTWe present a comprehensive study of the parameter determination of magnetic resonance sounding (MRS) models in a joint MRS and transient electromagnetic (TEM) data analysis scheme. The parameter determination is assessed by calculating the model parameter uncertainties based on an a posteriori model covariance matrix. An entire MRS data set, dependent on pulse moment and time gate values, together with TEM data, is used for all analyses and realistic noise levels are assigned to the data.Sensitivity analyses are studied for the determination of water content as a key parameter estimated during inversion of MRS data. We show the results for different suites of (three‐layer) models, in which we investigate the effect of resistivity, water content, relaxation time, loop side length, number of pulse moments and measurement dead time on the determination of water content in a water‐bearing layer. For all suites of models the effect of a top conductive and a top resistive layer are compared. Moreover, we analyse all models for a long (40 ms) and short (10 ms) measurement dead time. The effect of noise level on the parameter determination is also analysed.We conclude that, in general, the resistivity of the water‐bearing layer (layer of interest, LOI) does not affect the determination of water content in the LOI but the resistivity of the top layer increases depth resolution; the water content of the LOI does not influence its determination considerably in cases where the signal has a relatively long relaxation time in the LOI; determination of the water content in the LOI is improved by increasing the relaxation time of the signal in the LOI; short measurement dead time will improve the parameter determination for signals with a relatively short relaxation time; increasing loop side length and the number of pulse moments do not necessarily improve the parameter determination.