DEVELOPMENTS OF NONCONTACT DATA-ACQUISITION TECHNIQUES IN ELECTRICAL AND ELECTROMAGNETIC EXPLORATIONS

This paper describes two non-contact electrical and electromagnetic ex ploration techniques. One is a surface electrical exploration techniqu e using capacitive electrodes, which we recently developed. A capaciti ve electrode allows both injecting an electric current into the ground and measuring the ground's electric potential, which allows us to con duct non-contact surface electrical profiles. The other method is bore hole 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 acquisi tion systems for these two techniques and conducted two field experime nts. The results of the first experiment show that it is possible to t rail 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 usin g dry holes or boreholes lined with plastic casing.