Electrical Resistivity Imaging

Electrical Resistivity Imaging (ERI), also known as Electrical Resistivity Tomography (ERT) and DC Resistivity, is widely used in environmental, geotechnical, groundwater and mining exploration applications.

ERI involves the pumping of a direct (DC) electrical current into the ground through a pair of metal ground electrodes and measuring the resulting potential differences between a second pair of ground electrodes. Although the method is reliable and very common, it is often inappropriately simplified. There are significant limitations and parameter considerations that can affect the usefulness of the data. When considering an ERI survey it is best to consult with the experts at DMT to ensure your ERI survey will meet your goals. Electrode spacing, instrument power and electrode configuration are the key parameters in ensuring the depth and resolution goals of the investigation are met. The measured data are processed using commercially available software such as RES2DINV*. Processed ERI results are presented as ground resistivity cross-sections, where data from closely-spaced electrodes are plotted at shallow depths, and data from widely-spaced electrodes are plotted at deeper depths.

These resistivity cross-sections can be used to:

  • Infer rock and soil boundaries, fracture zones, lithology
  • Image man-made features such as landfills, foundations, mine workings, buried utilities
  • Map saltwater intrusions
  • Map areas containing contaminated soils, leachate from landfills/ponds/containment structures
  • Map the location and size of paleochannels
  • Measure the depth to bedrock and water table

Figure 1. An ERI cross section showing where contaminant associated with a pipeline rupture has migrated at least 20 metres laterally from the breach and 5 metres below ground surface.

*RES2DINV is a product of Geotomo Software Sdn. Bdh.