TERRAPUB Earth, Planets and Space

Earth Planets Space, Vol. 51 (No. 10), pp. 1005-1012, 1999

A computing method for 3D magnetotelluric modelling directed by polynomials

Pierre-André Schnegg

Institute of Geology, CH-2007 Neuchâtel, Switzerland

(Received November 2, 1998; Revised February 23, 1999; Accepted April 12, 1999)

Abstract: A computational method for automatic 3D MT modelling is described. Making use of a recent publicly available forward algorithm, our method allows unattended search for a 3D conductivity model. The geometry of the conductivity features is described by a set of mathematical functions of the horizontal coordinates x and y and of a fixed number of parameters. Starting from a presumed conductivity distribution, our scheme automatically varies the parameters in a steepest descent control loop, until the misfit between the model response and the measured data reaches an allowable value. To illustrate the method, we apply it to MT and induction data gathered in the Swiss Alps and determine the depth and lateral extension of a highly conductive, graphite-bearing layer.

Corresponding author E-mail: pierre.schnegg@geol.unine.ch

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