When Is 1D 2D? Interpretation Of Geoelectrical Sections

Surface geoelectrical measurements are routinely used in environmental and mapping<br>geophysics. The methods are used for the investigation of waste deposits, detailed mapping<br>of aquifers in ground water source areas and mapping of raw materials. In Denmark, that<br>means gravel, sand and clay.<br>The geoelectrical data may be presented as apparent resistivity pseudosections for<br>interpretation by the geophysicist. A pseudosection shows an unfocused and distorted image<br>of the subsurface which can be a starting point for a qualitative interpretation.<br>Quantitative interpretation of geoelectrical data is done with the purpose of finding the<br>parameters of an assumed model. Model assumptions include layered (ID), horizontal<br>cylinders of arbitrary cross-section (20) or 3D bodies. Traditionally, geoelectrical soundings<br>are interpreted using 1D models and tools for such inversions are very well developed with<br>regard to speed and accuracy. Thus an initial interpretation can be accomplished quickly and<br>used for the planning of further field work.