基于虚拟波场的可控源三维电磁法正演

doi:10.11720/wtyht.2024.1124

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Abstract

This study converted the frequency-domain electromagnetic diffusion equation into the wave equation in the fictitious domain based on the transformation relationship between the diffusion field and the fictitious wave field,achieving the numerical calculation of the electromagnetic field in the fictitious wave field.By introducing the complex frequency shifted perfectly matched layer(CFPML) boundary condition,the storage capacity of the computer memory decreased.Furthermore,by encompassing the air layer in the calculation domain,the complex processing of the ground-air interfaces was avoided.Compared to the uniform half-space analytical solution,the algorithm proposed in this study had relative errors of less than 3.5% and thus is effective and correct.Finally,the numerical simulation of a typical geoelectric model indicated that the 3D electromagnetic responses of multiple frequencies can be obtained through single forward modeling,suggesting an elevated calculation efficiency.The numerical simulation results also exhibit that the apparent resistivity calculated based on the fictitious wave field is insensitive to the field source effect and thus can effectively identify anomaly boundaries.

Key words： controlled-source electromagnetic method fictitious wave field finite difference method 3D forward modeling

Received: 27 August 2023 Published: 21 October 2024

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	Zhi-Qiang JIANG
	Chao LIN
	Ting-Wei YANG
	Xiao-Bin NING

Cite this article:

Zhi-Qiang JIANG,Chao LIN,Ting-Wei YANG, et al. Forward modeling of a controllable-source 3D electromagnetic method based on fictitious wave field[J]. Geophysical and Geochemical Exploration, 2024, 48(5): 1348-1358.

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https://www.wutanyuhuatan.com/EN/10.11720/wtyht.2024.1124 OR https://www.wutanyuhuatan.com/EN/Y2024/V48/I5/1348

Spatial discretization of electromagnetic field in fictitious wave field

Schematic diagram of a uniform half space model

Response and relative error plots of the electric field component E_x(a、b) and magnetic field component H_y(c、d) with a frequency of 100 Hz in a uniform half space

xz surface wave field snapshot of fictitious electric field component E'_x at different times in a uniform half space
a—t=0.12 s;b—t=0.16 s;c—t=0.25 s;d—t=0.27 s;e—t=0.28 s;f—t=0.30 s

Schematic of low resistance 3D anomalous body model in uniform half space

xz surface wave field of fictitious electric field component E'_x at different times with one low resistance anomalous body
a—t=0.38 s;b—t=0.43 s;c—t=0.44 s;d—t=0.45 s;e—t=0.49 s;f—t=0.50 s

Contour map of electric field component E_x and apparent resistivity of 16 Hz with one low resistance anomalous body
a—apparent resistivity contour line;b—electric field component E_x contour line

Contour map of electric field component E_x and apparent resistivity of 64 Hz with one low resistance anomalous body
a—apparent resistivity contour line;b—electric field component E_x contour line

Schematic of a 3D anomalous body model with one low resistance and one high resistance in a uniform half space
a—xy plane cross-section;b—xz plane cross-section

xz surface wave field snapshot of fictitious electric field component E'_x at different times with one low resistance and one high resistance anomalous body
a—t=0.43 s;b—t=0.44 s;c—t=0.46 s;d—t=0.47 s;e—t=0.49 s;f—t=0.50 s

Contour map of electric field component E_x and apparent resistivity of 16 Hz with one low resistance and one high resistance anomalous body
a—apparent resistivity contour line;b—electric field component E_x contour line

Contour map of electric field component E_x and apparent resistivity of 64 Hz with one low resistance and one high resistance anomalous body
a—apparent resistivity contour line;b—electric field component E_x contour line

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