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Negi, Tateyuki*; Mizunaga, Hideki*; Asamori, Koichi; Umeda, Koji
Exploration Geophysics, 44(3), p.145 - 155, 2013/09
Times Cited Count：1 Percentile：4.94(Geochemistry & Geophysics)This paper presents a fast algorithm for electromagnetic inversion. The algorithm is distinct for the level of accuracy it attains when bypassing the sensitivity matrix update. A common sensitivity matrix for homogeneous half-space is used in all of the iterations. Instead of a fixed sensitivity matrix, the Laplace filter coefficients at each element are updated based on the spatial differences of resistivity calculated by a reconstructed structure derived from the former iteration. This substitution is expected not only to reduce the computation time required for large-scale inversions, such as those for three-dimensional surveys, but also to allow reconstruction for sharp boundaries in resistivity structures. This algorithm was applied to three-dimensional magnetotelluric inversion in order to confirm the effectiveness. This paper reports the results of several synthetic examples using different resistivity models and conditions.
Tokuyasu, Shingo; Matsuoka, Toshiyuki; Mizunaga, Hideki*; Sugimoto, Yoshihiro*
no journal, ,
no abstracts in English
Negi, Tateyuki*; Mizunaga, Hideki*; Asamori, Koichi; Umeda, Koji
no journal, ,
Electromagnetic surveys have been widely used for several decades in geothermal, mining and oil exploration or disaster prevention. More recently, three-dimensional surveys have been increasingly carried out. However, they require the large-scale inversion consuming significant computation time. Traditional inversion algorithms based on the linear sensitivity matrix consume time to update the sensitivity matrix in the several iterations. In the presentation, we show a rapid calculation algorithm for the electromagnetic inversion procedure that allows to bypass updating of the sensitivity matrix. In the procedure, a fixed sensitivity matrix for a homogeneous half-space is used in all iterations. Instead of the fixing sensitivity matrix, the Laplace filter coefficients in the each element are updated based on the resistivity smoothness calculated by reconstructed structure. This substitution is not only expected to reduce the computing time required for the large-scale inversion such as for the three dimensional surveys, but also expected to allow the reconstruction for sharp boundary structure. We applied the algorithm for the three dimensional magnetotelluric inversion algorithms to confirm the effectiveness. In the presentation, we show the calculation results using several synthetic data examples with different structures and conditions.
Negi, Tateyuki*; Mizunaga, Hideki*; Asamori, Koichi; Umeda, Koji
no journal, ,
no abstracts in English
