Electrical Resistivity Primer

OutlineMotivationGeophysical ImagingSubsurface Electrical PropertiesThe Electrical Resistivity MethodSurveys and Data DisplayTimelapse Electrical Resistivity

Data display: Pseudo Sections

A resistivity measurement results in an apparent resistivity which is used in an inverse program to give a distribution of electrical properties of the subsurface. However, it is useful to have a graphical representation of the data. One commonly used representation of 2D profiles is the so called pseudo section.

In a pseudo section we associated the values (or more commonly, the log of the values) of apparent resistivity with a specific x,y location. The x location is given by the mid-point of the electrodes used to make that measurement. The y location is proportional to the spacing of the electrodes. Thus, the larger the spacing, the larger the y location. We then contour these values to give a pseudo section

The pseudo section is useful for initial quality assessment. For instance, if there is a bad electrode a pseudo section will show this. A pseudo section also gives a first visual indication of heterogeneity. However, the pseudo section over a specific subsurface will be different for different types of arrays, and the pseudo section should not be used for data interpretation.

Pseudo section