Two-dimensional nonlinear conjugate gradient inversion of ZTEM
Zhi-Bo XU1, Han-Dong TAN2
1. Civil and Transportation College of Beihua University, Jilin 132013, China 2. School of Geophysics and Information Technology, China University of Geoscience (Beijing), Beijing 100083, China
The ZTEM (Z-Axis Tipper Electromagnetics) is a frequency-domain airborne electromagnetic method that results from natural sources. It has the feature that the vertical component of magnetic field is measured from a moving helicopter platform and the horizontal component of magnetic field is measured at a reference station on the ground. In addition, it has the advantages of deep exploration, fast speed, low cost and large coverage area. This paper realizes the 2D finite difference forward modeling and NLCG inversion of ZTEM. The object of the study is the tipper data. The direct calculation of Jacobian matrix is avoided by solving the "quasi-forward" problem in the inversion process. The stability and reliability of the 2D NLCG inversion of ZTEM tipper data are verified by the trial calculation of synthetic data inversion of theoretical model. A comparison with the inversion result of impedance data of magnetotelluric (MT) TE mode shows that the ZTEM tipper inversion is superior to the MT impedance inversion in the constraint of the lateral boundary of the anomalous body.
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