rafleiðnimælingu

Rafleiðnimæling is a geophysical exploration method used to determine the electrical resistivity of the subsurface. This technique relies on the principle that different geological materials have varying abilities to conduct electricity. By injecting electrical current into the ground through one or more electrodes and measuring the resulting potential difference at other electrodes, the resistivity distribution can be inferred.

The fundamental equation governing this process is Ohm's Law, adapted for distributed current injection and potential measurement. The apparent resistivity, which is the resistivity value calculated assuming a homogeneous subsurface, is then determined using specific geometric configurations of the electrodes. Common electrode arrays include Wenner, Schlumberger, and dipole-dipole configurations, each offering different sensitivities to subsurface variations at various depths and lateral extents.

The interpretation of resistivity data involves inverting the measured apparent resistivities to produce a model of the subsurface resistivity structure. This can be achieved using various numerical modeling and inversion algorithms. Changes in resistivity are often associated with variations in lithology, the presence of fluids (like groundwater or hydrocarbons), porosity, saturation, and temperature.

Rafleiðnimæling is widely applied in hydrogeology for groundwater exploration and mapping aquifer boundaries, in mining for locating mineral deposits, in environmental studies for detecting contaminant plumes and mapping landfill sites, and in geotechnical investigations for assessing soil and rock properties. Its non-invasive nature makes it a valuable tool for subsurface characterization without the need for extensive drilling. The effectiveness of rafleiðnimæling can be influenced by the presence of conductive surface layers or noise from man-made electrical sources.