Depth of detection of highly conducting and volume polarizable targets using induced polarization
A. Apparao, G.S. Srinivas, V. Subrahmanya Sarma, P.J. Thomas, M.S. Joshi and P. Rajendra Prasad
Journal name: Geophysical Prospecting
Issue: Vol 48, No 5, September 2000 pp. 797 - 813
Info: Article, PDF ( 943.07Kb )
We define the apparent frequency effect in induced polarization (IP) as the relative difference between apparent resistivities measured using DC excitation on the one hand and high-frequency excitation (when the IP effect vanishes) on the other. Assuming a given threshold for the minimum detectable anomaly in the apparent frequency effect, the depth of detection of a target by IP can be defined as that depth below which the target response is lower than the threshold for a given electrode array. Physical modelling shows that for the various arrays, the depth of detection of a highly conducting and volume polarizable target agrees closely with the depth of detection of an infinitely conducting and non-polarized body of the same shape and size. The greatest depth of detection is obtained with a two-electrode array, followed by a three-electrode array, while the smallest depth of detection is obtained with a Wenner array when the array spread is in-line (i.e. perpendicular to the strike direction). The depth of detection with a Wenner array improves considerably and is almost equal to that of a two-electrode array when the array spread is broadside (i.e. along the strike direction).