[H-TT17] New Developments in Shallow Geophysics

[HTT17-08] CCR survey using plate electrodes

*Chisato Konishi¹, Hiroshi Kisanuki¹, Dennis Wilkison (1.OYO Corporation)

Keywords:CCR survey, resistivity, plate electrode

The CCR (Capacitively coupled resistivity) survey system using dipole-cable has an issue of low sensitivity for estimating resistivity profile of shallow subsurface less than 2m in depth due to a limitation of dipole-cable length. A new system using cylinder electrode was developed (Konishi et al., 2018) to solve the problem. Because the length of the cylinder electrode is one eighth of the shortest dipole-cable length, it enables the separation between the transmitter and the receiver small; however, the signal was interfered by EM coupling between the receiver and the transmitter when the separation was too small. To resolve the new issue, which was probably associated with EM wave in the air, plate electrodes were developed and tested. The plate electrode is the same as long as the cylinder electrode and is placed only towards the ground. In the field experiment, we found that the EM coupling was significantly reduced by using the plate electrodes. Additionally, the measured apparent resistivity was comparable with the one measured by ordinary resistivity measurement with dipole-dipole array configuration using iron stakes placed at the center positions of the plate electrodes. Therefore, it is possible to obtain a resistivity profile from the surface to 10 m in depth effectively by the CCR survey using both the plate electrodes and the dipole-cables.