Study on step-by-step regularization inversion based on adaptive unstructured mesh
CHENG San1, ZHANG Zhiyong1, ZHOU Feng1,2, LI Man1, ZHAI Binjun1
1. School of Geophysics and Measurement-Control Technology, East China University of Technology, Nanchang, Jiangxi 330013, China; 2. Fundamental Science on Radioactive Geology and Exploration Technology Laboratory, East China University of Technology, Nanchang, Jiangxi 330013, China
Abstract：A step-by-step regularization inversion scheme based on adaptive mesh by taking two-dimensional magnetotelluric (MT) inversion as an example. In the initial stage of the inversion，coarse mesh is adopted for the inversion，and the ill-posedness of the inversion is decreased by reducing the number of inversion elements. During the iterative inversion process，mesh is adaptively refined according to mesh refinement strategies to get better imaging of abnormal bodies. The inversion results of the previous mesh are used as the reference model and the initial model in the inversion of the next mesh，so as to ensure the model improvements along the correct direction of the inversion，and then improve the inversion stability and inversion results. Four mesh refinement strategies were proposed，including model sensitivity，model variation，model gradient and “edge-angle” detection. The characteristics of the four mesh optimization schemes are analyzed by Hessian matrix eigenvalue distribution，and the adaptive inversion results of four mesh refinement schemes are compared. Finally，the practicability of the adaptive inversion algorithm is proved by the inversion of synthetic model and field data.
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