Three-dimensional nonlinear regularized inversion of the induced polarization data based on the Cole-Cole model

The quantitative interpretation of induced polarization (IP) data in a complex three-dimensional (3D) environment is a very challenging problem . The analysis of IP phenomena is usually based on models with frequency dependent conductivity distri­ butions . In this paper, we develop a technique for 3D nonlinear inversion of IP data based on the Cole-Cole relaxation model. Our method takes into account, though in an approximate way, the nonlinearity of electromagnetic induction and IP phenom ena, and inverts the observed data for the Cole-Cole model paramet ers. The solution of the 3D IP inverse problem is based on both smooth and focusing regularized inversion , which helps to generate more reliable images of the subsurface structures. The method is tested on synthetic models with anomalous conductivity and intrinsic chargeability, and is also applied to a practical 3D IP survey. We demon strate that both the electrical conductivity and the chargeability distributions, as well as the other pa­ rameters of the Cole-Cole model , can be recovered from the observed IP data simultaneously. The recovered parameters of the Cole-Cole model can be used for the discrimination of the different types of minerali zation , which is an important goal in mineral exploration. © 2004 Published by Elsevier B.V.