Electrical Resistivity Tomography (ERT) is a versatile geophysical method suitable for a broad range of applications and environments such as groundwater prospecting, mineral exploration, geological mapping and geotechnical investigations.
Variations in subsurface electrical resistivity (or conductivity) typically correlate with variations in lithology, water saturation, fluid conductivity, porosity and permeability, which may be used to map stratigraphic units, geological structure, sinkholes, fractures and groundwater.
The acquisition of electrical resistivity tomography data involves the injection of current into the ground via a number of electrodes. The field set-up requires the deployment of an array of regularly spaced electrodes, which are connected to a central control unit via multi-core cables. Resistivity data are then recorded via complex combinations of current and potential electrode pairs to build up a pseudo cross-section of apparent resistivity beneath the survey line. The depth of investigation depends on the electrode separation and geometry, with greater electrode separations yielding bulk resistivity measurements from greater depths.
An electrical resistivity cross section displaying measured resistivities
Applications of Electrical Resistivity Tomography: - Geological mapping - Geotechnical pre-investigation - Groundwater prospecting - Mineral exploration - Mapping and monitoring of contaminants - Geothermal prospecting - Sub-bottom mapping of marine environments - Monitoring of permafrost - Archaeological Surveys