Two-dimensional magnetotelluric forward and inverse analysis of the finite-difference method with staggered sampling
ZHOU Wu1(), LUO Wei2,3(), LAN Xing3, JIAN Xing-Xiang2
1. Gansu Provincial Transportation Planning, Survey & Design Institute Co., Ltd., Lanzhou 730030, China 2. School of Geophysics,Chengdu University of Technology, Chengdu 610000, China 3. Sichuan Metallurgical Geological Survey and Design Group Co., Ltd., Chengdu 610000, China
The staggered sampling grid can automatically ensure that the electromagnetic field distribution obeys the law of energy conservation. Based on the staggered sampling grid, the authors deduced the two-dimensional finite difference forward process of magnetotelluric survey, and realized the two-dimensional forward program. Compared with one-dimensional analytical solution, the algorithm is proved to be correct and has high accuracy. Then, using the finite memory quasi Newton optimization algorithm, the authors realized the staggered sampling grid finite difference two-dimensional inversion. The correctness of the inversion algorithm was verified by theoretical model inversion, which shows that the efficiency of quasi Newton inversion with finite memory is better than that of nonlinear conjugate gradient. Finally, the deep structure of the survey area was found through the inversion and interpretation of the magnetotelluric data from Guanegou in Dangchang County, which shows that the algorithm has strong practicability.
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doi: 10.1111/j.1365-246X.2011.05347.x