1. School of Geosciences and info-physics, Central South University, Changsha, Hunan 410083, China; 2. Hunan Key Laboratory of Nonferrous Resources and Geological Disaster Exploration, Changsha, Hunan 410083, China; 3. Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring (Central South University), Ministry of Education, Changsha, Hunan 410083, China; 4. Technical Innovation Center of Coverage Area Deep Resources Exploration, Ministry of Natural Resources, Hefei, Anhui 230001, China
Abstract：In terms of magnetotelluric (MT) exploration, when the geometric size of the near-surface three-dimensional abnormal body with inhomogeneous electrical property is much smaller than the skin depth of the electromagnetic wave, the impedance tensor will be seriously distorted. If this effect continues, the electrical structural model obtained by inversion will deviate from the true tectonic model, which will further affect the subsequent geological interpretation. Most of the traditional distortion correction methods assume that the regional structure is one-dimensional or two-dimensional, while the actual regional structure is generally three-dimensional. Therefore, this paper starts from the amplitude phase tensor decomposition of impedance tensor, uses the feature that the amplitude tensor decomposition parameters without distortion are highly similar to the phase tensor decomposition parameters, and establishes an objective function according to the sum of the corresponding decomposition parameter differences. Furthermore, the paper searches for the distortion parameters by improving the particle swarm algorithm and takes the objective function value as the fitness of the particles. As a result, the MT galvanic distortion correction in which the regional structure is arbitrary in dimensions is realized. In addition, the paper proposes an MT galvanic distortion correction method that requires no assumption of the dimension of regional structure and has wider adaptability. Finally, the method is applied to calculate the three-dimensional model and filed data, and the results verify the effectiveness, correctness, and practicability of the method.
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