Nuclear Magnetic Resonance (NMR) decay parameters show a significant dependency on the Larmor frequency related to the strength of the static field of the method. A straight forward frequency downscaling of the results obtained with the higher field applications in the lab down to the very low frequency range of the Earth field (EF) is not possible. We investigated the EFNMR relaxation times of natural sand and different synthetic sand-clay-mixtures and compare these with relaxation times at high fields i.e. Larmor frequencies. We find, that the EF T2* decay time can be used as a measure for characterizing the water filled pore space in spite of the existence of small internal field gradients. This finding is very useful for instance for the application of the Magnetic Resonance Sounding method for groundwater assessment from the Earth surface. The field cycling of T1 measurements show that a downscaling from the higher field NMR down to the EFNMR is in principle possible, if the surface relaxivity of the material to be investigated is known.


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