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 profilin g mode in the search for lateral variations of resistivity down to dep ths of a few tens of metres. Theoretical computations show that plotti ng simple pseudosections of offset measurements over faults is suffici ent to reveal the fault position. The method is subsequently applied i n the field for locating a buried fault in coal measures. Although off set pseudosections are often all that is required, apparent resistivit y pseudosections are examined and compared to collations of 1D inversi ons of the sounding profile data and to computations over 2D models. I t is shown that apparent restivity pseudo-sections may present a rathe r misleading picture.