AMT地形影响与带地形反演研究

doi:10.11720/wtyht.2023.1033

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Abstract

This study designed a group of 2D peak-valley comprehensive terrain models with different widths and slopes and investigated the influence of differently undulating terrains in mountainous areas on the audiomagnetotelluric (AMT) data and corresponding distortion characteristics from seven aspects, namely polarization modes, frequency, positions of measurement points, the width of a mountain top, the elevation difference and slope of terrain, and phase curves. The results are as follows. The transverse magnetic mode (TM mode) is more susceptible to terrain than the transverse electric mode (TE mode). The undulating terrain has little influence on the high-frequency parts of AMT data but has a great influence on their low-frequency parts. The apparent resistivity and phase of different frequency points at a measurement point reflect the comprehensive influence of all terrains within the skin depth level rather than just the influence of a single mountain peak or valley near the measurement point. Measurement points located at the mountain peaks are more easily affected by terrains than those in the valleys. Moreover, narrower mountain tops correspond to greater elevation differences of terrain, and steeper terrain exerts greater influence. In addition, the comparison of the 2D_TE results of the inversion considering and not considering terrains show that the 2D inversion considering terrains can effectively eliminate the influence of terrain. The 2D inversion considering terrains was carried out for measured AMT data. As indicated by the inversion results, the 2D inversion considering terrains can effectively eliminate the false high and low resistance anomalies and relieve the "hanging surface" phenomenon of signals, and the results corresponded well with the horizons with encountered manganese of three boreholes.

Key words： AMT terrain model topographic influence 2D inversion with terrain

Received: 26 January 2022 Published: 24 February 2023

ZTFLH:

P631

Corresponding Authors: GUO Shu-Jun E-mail: czp1990@126.com;279464376@qq.com

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	Articles by authors
	Zheng-Pu CHENG
	Shu-Jun GUO
	Qiang WEI
	Le ZHOU
	Ming LEI
	Shu LI

Cite this article:

Zheng-Pu CHENG,Shu-Jun GUO,Qiang WEI, et al. Audiomagnetotelluric data: Influence of terrain and the inversion considering terrain[J]. Geophysical and Geochemical Exploration, 2023, 47(1): 146-155.

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https://www.wutanyuhuatan.com/EN/10.11720/wtyht.2023.1033 OR https://www.wutanyuhuatan.com/EN/Y2023/V47/I1/146

Schematic diagram of peak valley terrain model A

The forward sampling frequency by Model A

The forward apparent resistivity and phase curves of TE and TM by model A(red circle is TE curve, blue triangle is TM curve)

Schematic diagram of peak valley terrain model with gradual edge change

2D_TE inversion apparent resistivity profile of model B, C and D
a—2D_TE inversion apparent resistivity profile by without terrain of model B; b—2D_TE inversion apparent resistivity profile by without terrain of model C; c—2D_TE inversion apparent resistivity profile by without terrain of model D; d—2D_TE inversion apparent resistivity profile by with terrain of model B; e—2D_TE inversion apparent resistivity profile by with terrain of model C; f—2D_TE inversion apparent resistivity profile by with terrain of model D

Actual AMT survey line deployment

Statistics of physical properties of rocks and ores in the exploration area

Apparent resistivity curve of measuring points on the peak of measured AMT profile(red circle is TE curve, blue triangle is TM curve)

Apparent resistivity and phase pseudo section of measured AMT profile (upper: TE mode; down: TM mode)

2D_TEinversion results of AMT line in a mountainous area of manganese ore without terrain(a) and with terrain(b)

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