Electrical Techniques
Spectral Induced Polarisation
Outline
Spectral IP surveys involve measurement of the magnitude and relative phase of the polarisation voltage that results from the injection of an alternating current into the ground. Polarisation voltages primarily result from electrochemical action (ionic exchange) within the pores and pore fluids of the material being energised. Measurements of the relative phase shift between the transmitted current and the measured signal and the magnitude of the polarisation voltage are taken over a range of different frequencies, typically between 0.125 and 1000Hz. This results in a distinct IP response spectrum or 'dispersion' at each measurement position that can be used to determine various parameters of the subsurface materials such as relaxation time and chargeability. Spectral IP is currently being tested in the detection of hydrocarbon contamination.
