2-D inversion of MT data with a variable model geometry

S U M M A R Y An inversion algorithm which takes into account the varying geometry in magnetotelluric models is considered. The particular problem of estimating the shape of the interface between two different conductivities is studied. This boundary is represented by an implicit function and its parameters are calculated in the inversion process. The assumption of using such a function allows us to simplify the computation of the sensitivity matrix of the model, and gives a stronger numerical stability to the inversion procedure. The finite element method is used to solve the forward problem. The inversion algorithm is based on a Bayesian approach that allows the introduction of a priori information. Several examples with simple geometries show the possibilities offered by the algorithm.