Developments of Non-contact Data Acquisition Techniques in Electrical and Electromagnetic Explorations

This paper describes two non-contact electrical and electromagnetic exploration techniques. One is surface electrical exploration technique using a capacitive electrodes we recently developed. A capacitive electrode enables both injecting an electric current into the ground and measuring the ground's electric potential, which allow us to conduct non-contact surface electrical profile. The other method is borehole electromagnetic (EM) tomography, which transmits a magnetic field and measures the secondary magnetic field. It does not require direct contact with the ground. The authors developed prototype data acquisition systems for these two techniques and conducted two field experiments. The results of the first experiment show that it is possible to trail a multi-channel capacitive electrode array having a speed of 3.6 km/h and explore to a depth of 6 m. The second experiment demonstrated that EM tomography can map the underground resistivity structure using dry holes or boreholes lined with plastic casing.