Two-dimensional magnetotelluric smooth focusing inversion based on optimization strategy
BAI Ningbo1, ZHOU Junjun2, HU Xiangyun1,2
1. Key Laboratory of Geological Survey and Evaluation of Ministry of Education, China University of Geosciences(Wuhan), Wuhan, Hubei 430074, China; 2. Institute of Geophysics & Geomatics, China University of Geosciences(Wuhan), Wuhan, Hubei 430074, China
Abstract：On the basis of previous studies, this paper proposes a new inversion objective functional with the purposes of realizing rapid and stable inversion and obtaining clear geological interfaces. It adopts the smoothest model and the minimum support gradient model functional to constrain the data objective functional. Solved by the Gauss-Newton method, the new inversion objective functional enables the smooth focusing inversion of two-dimensional magnetotelluric data. The smooth focusing inversion can not only present clear geological interfaces but also avoid the distortion of structural morphology caused by focused inversion to a certain extent. In the process of inversion iteration, we adopt the optimization strategy of improving the Morozov discrepancy principle with the Nelder-Mead optimization algorithm to obtain the appropriate regularization factor, which greatly accelera-tes the inversion convergence. Finally, the proposed inversion method is verified with a typical model and real data and also compared with other inversion strategies. The inversion results show that for typical model inversion, the algorithm in this paper outperforms the others in agreeing with the model, with the convergence curve decreasing rapidly and the geological body interface being clear. The inversion results of real data further verify the reliability and effectiveness of this algorithm.
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