Response Characteristics of 3D Tensor CSAMT

doi:10.19657/j.geoscience.1000-8527.2022.038

Abstract

Abstract:

Tensor CSAMT can fully describe three-dimensional (3D) geoelectric information, and is more suitable for geological exploration under complex geological conditions. Strategy of decomposing the total field into primary and secondary field is adopted here, and the large-scale linear equations are formed by different approximate differentiation. The 3D forward modeling results of tensor CSAMT are obtained according to these equations. By calculating the response of low-resistivity and high-resistivity targets, the Kania apparent resistivity and apparent impedance phase show low and high anomaly for low-resistivity and high-resistivity body, respectively. The frequency of which the apparent impedance phase reaches the extreme value is higher than that when the apparent resistivity reaches the extreme value. Tensor CSAMT is more sensitive to low-resistivity body than to high-resistivity body. Under the same condition, the abnormal area position of high-resistivity body moves upward compared with low-resistivity body. A survey case in the study area shows that the underground abnormal body can be qualitatively judged via the Kania apparent resistivity anomaly, which facilitates geological problem solving. This study provides a basis for tensor CSAMT 3D inversion.

Key words: finite difference method, tensor CSAMT, forward response

CLC Number:

P631.3

LIU Xiao, SONG Shuanglin, TAN Handong, YU Feiyang, WANG Wanhui, YAN Yujun, LEI Xiang. Response Characteristics of 3D Tensor CSAMT[J]. Geoscience, 2023, 37(01): 84-89.

Figures/Tables 8

Fig.1 Spatial sampling of Yee’s grid

Fig.2 Sketch diagram of the source excitation and reception

Fig.3 Schematic diagram of the combined model

Fig.4 Variation curve and pseudo contour map of Kania apparent resistivity for the combined model

Fig.5 Variation curve and pseudo contour map of impedance phase for the combined model

Fig.6 Pseudo contour map of Kania apparent resistivity for the measured data

Fig.7 Surveyed geological cross-section [14]

Fig.8 Pseudo contour map of Kania apparent resistivity for the surveyed geological cross-section

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