Resistance methods


They still belong to the most fundamental and in the past the most used geophysical methods. They measure the spatial variability of apparent specific electrical resistance. It is a method of vertical electrical sounding (VES) and resistance profiling (RP).


Vertical electrical sounding

It is used to detect changes of apparent electrical resistivity of the ground towards the depth. The measurements are usually carried out along profiles; the length of the electrode spacing is selected according to the desired depth range. For relatively simple terrain methodology and the possibility of quantitative interpretation of various conducting depths, this method is used mainly in solving geological problems in semi-horizontally layered environment. If measurements VES are carried out on parallel profiles, it is possible from the results of these measurements to compile a dimensional image of the allocation of major resistance interfaces.


Resistance profiling

This method determines the variability of apparent electrical resistivity in the horizontal direction. Digging depth of measurement is given by the size of the electrode system and directly depends on its dimensions.

From the results of resistance profiling system in parallel profiles we can draw a surface map. This map shows the areal variability of electrical resistivity in the near-surface layer, whose thickness corresponds to the size of the used electrode system. Resistance profiling method is mainly used for searching vertical resistive interfaces.

In combination of method VES and RP, acquired data complement each other with new information, while resistance maps and structural models of the ground are more consistent, more detailed. From obtained measurements vertical incisions can be assembled, which may contain either the position of resistance interfaces, which usually correspond to significant geological strata, or location of tectonic fault lines.