Application of Electrical Resistivity Tomography Method to the Mapping of Explored Caves and Detection of Possible New Chambers: Case Studies from Greece

Cave detection and mapping is one of the most common targets of the resistivity method since the infinite resistivity of the air filled void of the cave is at a high contrast to the resistivity of any geological structure. In the case studies presented in this work (Maroneia and Andritsa, Greece) the caves are formed in limestone because of the karstification in addition to the local tectonics.

The geophysical method applied in both case studies is the Electrical Resistivity Tomography (ERT). The existing chambers have been observed in the resistivity models and new chambers are detected.

However, resistivity values attributed to the caves are of wide range. In Maroneia values of several thousand of Ohm.m have been measured while in Andritsa the values characterizing the chambers are small (maximum of 1610 Ohm-m).

The different behaviour of resistivities can be explained by the different geological formation hosting the caves and emphasizes the need for calibration measurements. This can be overcome with ERT measurements on the same geological formation but far from the surveyed area in order to measure the resistivity of the formation itself. In this case a forward modelling will suggest the expected values in the presence of a void.