Finite-difference modelling of magnetotelluric fields in two-dimensional anisotropic media |
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Authors: | Josef Pek Tomá Verner |
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Institution: | Geophysical Institute, Academy of Sciences of the Czech Republic, BočníII/1401, 14131 Prague 4—Spořilov, Czech Republic |
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Abstract: | An algorithm for the numerical modelling of magnetotelluric fields in 2-D generally anisotropic block structures is presented. Electrical properties of the individual homogeneous blocks are described by an arbitrary symmetric and positive-definite conductivity tensor. The problem leads to a coupled system of partial differential equations for the strike-parallel components of the electromagnetic field. E x, and H x These equations are numerically approximated by the finite-difference (FD) method, making use of the integro-interpolation approach. As the magnetic component H x, is constant in the non-conductive air, only equations for the electric mode are approximated within the air layer. The system of linear difference equations, resulting from the FD approximation, can be arranged in such a way that its matrix is symmetric and band-limited, and can be solved, for not too large models, by Gaussian elimination. The algorithm is applied to model situations which demonstrate some non-trivial phenomena caused by electrical anisotropy. In particular, the effect of 2-D anisotropy on the relation between magnetotelluric impedances and induction arrows is studied in detail. |
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Keywords: | 2-D structures electrical anisotropy finite-difference method magnetotelluric sounding |
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