Magnetic Resonance Sounding

Magnetic resonance sounding (MRS) works according to the same principle as Magnetic Resonance Imaging (MRI), but instead of scanning the human body for hydrogen nuclei, MRS stratifies the earth with respect to its water content and hydraulic conductivity. MRS is dependent on the fundamental property called “spin”, which makes the hydrogen nuclei in water behave like small magnets. Under the influence of the Earth magnetic field, the hydrogen nuclei will align themselves like compass needles in the direction of earth magnetic field. An electromagnetic pulse is then created in a cable loop, which will turn the magnetization of the hydrogen nuclei in the resulting field direction. When the pulse is terminated, the magnetization of the hydrogen nuclei returns back to the Earth’s magnetic field direction, while creating a secondary relaxation field. The relaxation signal is measured in the same loop, where the initial amplitude is directly proportional to the amount of water in the ground and the decay time is related to the ground permeability. The depth of investigation is a function of the coil diameter. By gradually increasing the pulse moment, the water content and hydraulic conductivity distribution with depth can be estimated. MRS has a maximum penetration depth to about 150 m and it is possible to measure 1-2 sites per day.
At GeoVista we have access to a MRS-instrument (Numis-Plus; Iris Instruments) in cooperation with Luleå university of technology.

Reference projects:

– Groundwater exploration in Gotland
– Well siting and optimization of a groundwater supply in the city of Luleå

MRS survey on Gotland.