Modelling and inversion of electromagnetic data using an approximate plate model |
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| Authors: | Markku Pirttijärvi Risto Pietilä Aimo Hattula Sven-Erik Hjelt |
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| Institution: | Institute of Geosciences, Department of Geophysics, University of Oulu, PO Box 3000, 90014 Oulu, and;Outokumpu Mining Oy, 83501 Outokumpu, Finland |
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| Abstract: | This paper presents a computational method for the interpretation of electromagnetic (EM) profile data in the frequency domain using a thin plate model within a two-layer earth. The modelling method is based on an integral equation formulation, where the conductor is represented by a lattice structure composed of two-dimensional surface elements. Several approximations are used to simplify the theoretical basis and to decrease the computation time. The simple parametric model allows efficient use of optimization methods. We employ a linearized inversion scheme based on singular value decomposition and adaptive damping. The new forward computation method and the parameter optimization are combined in the computer program, emplates . The modelling examples demonstrate that the approximate method is capable of describing the characteristic behaviour of the EM response of a thin plate-like conductor in conductive surroundings. The efficacy of the inversion is demonstrated using both synthetic and field data. An optional depth compensation method is used to improve the interpreted values of the depth of burial. The results show that the method is cost effective and suitable for interactive interpretation of EM data. |
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