3D land CSEM with a single transmitter position

Abstract : Anthropogenic noise, cost and logistical constrains generally limit to the use of land CSEM to a single transmitter position for the deep imaging of the electrical conductivity. As the inversion of CSEM data in the near field using a single transmitter position suffers from critical sensitivity singularities, we proposed a robust inversion framework adapted to this ill-conditioned inversion problem. The framework relies specifically on a robust Gauss-Newton solver, several model parameter transformations to compensate for the heterogeneous sensitivities, and on the reformulation of the CSEM data under the form of a pseudo- MT tensor. We describe here the approach used for modelling and inversion implemented in our code POLYEM3D and the new pseudo-MT formulation. We illustrate its application on a pathological synthetic case inspired from Grayver et al. (2013) and then show the application of the process to a real CSEM dataset acquired in the context of thermal water prospection.