Shallow fault location in coal measures using offset Wenner resistivity profiling

The five-electrode resistivity configuration of Barker, who introduced the concept of offset resistivity measurements, is used in a profiling mode in the search for lateral variations of resistivity down to depths of a few tens of meters. Theoretical computations show that plotting simple pseudosections of offset measurements over faults is sufficient to reveal the fault position. The method is subsequently applied in the field for locating a buried fault in coal measures. Although offset pseudosections are often all that is required, apparent resistivity pseudosections are examined and compared to collations of 1D inversions of the sounding profile data and to computations over 2D models. It is shown that apparent resistivity pseudosections may present a rather misleading picture.