Normalized impedance function and the straightforward inversion scheme for magnetotelluric data
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This paper investigates the performance of normalized response function obtained by normalizing the Cagniard impedance function by a suitable factor and then rotating the phase by 45‡ to make it purely real for homogeneous half-space and equal to the square root of the half-space resistivity. Two apparent resistivity functions based on respectively the real and imaginary parts of this response function are proposed. The apparent resistivity function using the real part contains almost the same information as that yielded by the Cagniard expression while the one using the imaginary part qualitatively works as an indicator of the number of interfaces in the earth model. The linear straightforward inversion scheme (SIS), developed by the authors employing the concept of equal penetration layers, has been used to validate the proposed apparent resistivity functions. For this purpose, several synthetic and field models have been examined. Five synthetic models are studied to establish the veracity of the new functions and two well-studied published field data sets are inverted through SIS for comparison. We noticed that the new function and SIS compliment each other and lead to better understanding of the data information and model resolution.
KeywordsStraightforward inversion magnetotelluric apparent resistivity
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- Berdichevsky M N and Zhdanov M S 1984 Advanced theory of deep geomagnetic Sounding; (Elsevier, Amsterdam).Google Scholar
- Cull J P 1985 Magnetotelluric soundings over a Precambrian contact in Australia;Geophys. J. Roy. Astr. Soc. 80 661–675.Google Scholar
- Fisher F, Schnegg P A, Pegurion M and Le Quang B V 1981 An analytic one dimensional magnetotelluric inversion scheme;Geophys. J. Roy. Astr. Soc. 67 257–278.Google Scholar
- Gupta P K, Sri Niwas and Gaur V K 1996 Straightforward inversion scheme (SIS) for one-dimensional magnetotelluric data;Proc. Indian Acad. Sci. (Earth Planet. Sci.) 105 413–429.Google Scholar
- Jones A G and Hutton R 1979 A multi-station magnetotelluric study in southern Scotland I. Fieldwork, data analysis and results;Geophys. J. Astr. Soc. 56 329–349.Google Scholar
- Loewenthal D 1975 Theoretical uniqueness of the magnetotelluric inverse problem for equal penetration discretizable models;Geophys. J. Roy. Astr. Soc. 43 897–903.Google Scholar
- Parker R L 1980 The inverse problem of electromagnetic induction: Existence and construction of solutions based upon incomplete data;J. Geophys. Res. 85 4421–4428.Google Scholar
- Weidelt P 1972 The inverse problem of geomagnetic induction;Z. fur. Geophys. 38 257–289.Google Scholar