Monitoring geomagnetic signals of groundwater movement using multiple underground SQUID magnetometers
1 University of Oxford, Department of Physics, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
2 UAPV, UMR1114 EMMAH, 84914 Avignon, France
INRA, UMR1114 EMMAH, 84914 Avignon, France
3 Université de Nice Sophia-Antipolis, Observatoire de la Côte d'Azur, Laboratoire Souterrain à Bas Bruit de Rustrel-Pays d'Apt (LSBB), La Grande Combe, 84400 Rustrel, France
Groundwater can influence the geomagnetic field measured underground in at least two key ways. The water levels in rock will determine its electrical conductivity, and thus change the magnitude of the telluric currents induced in the rock by changing magnetic fields generated in the ionosphere. This can be studied by using multiple magnetometers at different underground locations. Secondly the flow of water through rock will generate a small magnetic signal, of unknown magnitude, through the electrokinetic effect. SQUID magnetometry has the potential to allow passive studies of groundwater changes in complex systems such as karst. We have monitored geomagnetic signals using two SQUID magnetometers at the LSBB underground laboratory, and set an initial limit on the magnitude of the electrokinetic signal. We now plan to carry out a longer term measurement using three SQUID systems as well as fluxgate sensors to track changes in the gradient of the magnetic field across the underground complex.
© Owned by the authors, published by EDP Sciences, 2014
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