The principle of suppression

The principle of suppression is also very significant during the interpretation of the electrical soundings. This principle relates to those beds whose resistivities are intermediate between that of the enclosing beds. Such layers, as long as they do not have a great enough thickness, have practically no influence on the resistivity curve.

Example of suppression for a sounding of type Q

A case could be for example a surface layer of dry alluvium, then wet alluvium, both reposing on a conductive shaly substratum in such a case it becomes impossible to determine the depth of the substratum.

Example of suppression for a sounding of type A and H

This failure to define beds of intermediate resistivity is met frequently in ground water study. In this case the bed is altered bedrock on fresh bedrock. This bed as a resistivity intermediate between enclosing layers (bedrock and clayish alterites).

These principles of equivalence and suppression apply also in case of 3, 4, 5, etc. layers.