带地形的ZTEM倾子资料三维正反演研究

doi:10.11720/wtyht.2021.1349

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Abstract

ZTEM is a new-type frequency-domain airborne electromagnetic system which measures the magnetic fields that result from natural source. Tipper is adopted as a research parameter that relates the vertical magnetic field at the observation point to the horizontal fields at a ground based reference station, which can be used to perform large-scale structural exploration with topography. Based on the 3D finite-difference forward modeling and data-space OCCAM inversion of ZTEM, the authors have developed a frequency-domain 3D forward and inversion algorithm for ZTEM tipper data including surface tomography. At first, the forward code is verified for its correctness and applied to calculate and analyze the characteristics of 3D ZTEM abnormal response generated from undulate tomography. Then, the synthetic conductive models of 3D ZTEM inversion results including peak and valley terrain show that the algorithm can get the inversion models which are close to the underground real conductive structure; especially, it has an ideal constraint effect on the horizontal boundary of the underground object. At last, the results of synthetic example are compared with the results from 3D ZTEM inversion with no tomography implications to demonstrate the validity of the data-space OCCAM approach for inverting tipper data of ZTEM.

Key words： ZTEM tipper undulate topography 3D forward modeling and inversion data-space method airborne electromagnetic survey

Received: 14 July 2020 Published: 27 July 2021

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	Articles by authors
	Zhi-Qiang LI
	Yang SUN
	Han-Dong TAN
	Cheng-Ke ZHANG

Cite this article:

Zhi-Qiang LI,Yang SUN,Han-Dong TAN, et al. 3D forward modeling and inversion of ZTEM tipper data including surface topography[J]. Geophysical and Geochemical Exploration, 2021, 45(3): 758-767.

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https://www.wutanyuhuatan.com/EN/10.11720/wtyht.2021.1349 OR https://www.wutanyuhuatan.com/EN/Y2021/V45/I3/758

The (i,j,k) grid cell

The model of ZTEM Forward modeling

The tipper response comparison between the 2D finite difference modeling results and the 3D finite difference modeling results generated from 2D peak terrain model

The flow chart of data-space OCCAM inversion

Schematic diagram of peak terrain model in the view in xy direction(a), in the view in xz direction, and the view in xyzdirection

Contour of the ZTEM tipper response T_zx & T_zy at 50 Hz generated from 3D in peak terrain model (the white box is the outline of the model)

Contour of the ZTEM tipper response T_zx & T_zy at 50 Hz generated from 3D in valley terrain model (the white box is the outline of the model)

Schematic diagram of conductive prism model (peak terrain)

Results from the 3D inversion of tipper ZTEM data generated from 3D conductive prism model (peak terrain)
the top row—the results from the inversion of tipper data (ZTEM) with five frequencies;the second row—the results from the inversion of tipper data (ZTEM) including topography with five frequencies;the third row—the results from the inversion of tipper data (ZTEM) including topography with eight frequencies;the first column—the horizontal slices at 500 m depth;the second column—the vertical slices aty=0 m along the y axis;the third column—the vertical slices aty=0 m along the x axis;the black dashed lines—the prism margins

Schematic diagram of conductive prism model (valley terrain)

Results from the 3D inversion of tipper(ZTEM) data generated from 3D conductive prism model (valley terrain)
the top row—the results from the inversion of tipper data (ZTEM);the second row—shows the results from the inversion of tipper data (ZTEM) including topography;the first column—the horizontal slices at 650 m depth;the second column—the vertical slices atx=0 m along the y axis;the third column—the vertical slices aty=0 m along the x axis;the black dashed lines—the prism margins

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