Resistivity methods - DC and TEM with examples and comparison from the Reykjanes penisula and Öxarfjörður, Iceland

Abstract

Resistivity methods have for a long time been proven as the most successful method in geothermal exploration, due to the resistivity of rocks in geothermal environment being chiefly controlled by parameters that correlate to the geothermal activity. The most important method for measuring the resistivity in the uppermost kilometre was for a long time the DC resistivity method, especially with the Schlumberger configuration. It was in the 1990’s replaced by the TEM method, more specifically the central loop TEM sounding method, as the routine method for the exploring the uppermost kilometre. Description is given of both methods and their differences discussed. Then examples are taken from two geothermal areas in Iceland, the outer Reykjanes Peninsula and the Öxarfjördur area, where surveys using both methods have been done. The results are discussed and conclusions drawn that confirm the advantage of TEM over the DC method.