音频大地电磁测深法数据质量监控——基于EH4测量电极对数据质量影响因素分析

doi:10.11720/wtyht.2025.1444

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Abstract

The Audio-frequency Magnetotelluric (AMT) sounding method is an electrical exploration technique widely used for shallow to medium-depth geological investigations. Its data quality is influenced by various factors, including cultural electromagnetic interference, electrode polarization, and grounding resistance. This study focuses on the impact of electrode polarization and grounding resistance on AMT data quality. First, the mechanisms of electrode polarization and the influence of grounding resistance on apparent resistivity and impedance phase are theoretically analyzed. Then, based on measured data, the effects of electrode polarization and grounding resistance on apparent resistivity and phase curves are investigated. Finally, a comparative analysis of 2D inversion results from field data is conducted to reveal how grounding resistance affects geological interpretation. The results indicate that electrode polarization significantly degrades data quality in the low-frequency band, though this can be mitigated through data processing techniques, while its effect on high-frequency data is negligible. Unstable grounding resistance mainly influences the high-frequency range, causing notable reductions in apparent resistivity and phase, which gradually stabilize toward the low-frequency band. Moreover, unstable grounding resistance may lead to inversion results that deviate from the true geoelectrical structure, thereby resulting in erroneous geological interpretations. The findings of this study provide important guidance for field data acquisition and processing.

Key words： audio-frequency magnetotelluric (AMT) method data quality measurement electrode electrode polarization ground resistance geological interpretation

Received: 12 November 2024 Published: 23 October 2025

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	Jia-Yong LIN
	Zhi-Min XU
	Cong ZHOU

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Jia-Yong LIN,Zhi-Min XU,Cong ZHOU. Data quality monitoring of the audio-frequency magnetotelluric method: Analysis of factors influencing data quality based on EH4 measurement electrodes[J]. Geophysical and Geochemical Exploration, 2025, 49(5): 1126-1132.

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https://www.wutanyuhuatan.com/EN/10.11720/wtyht.2025.1444 OR https://www.wutanyuhuatan.com/EN/Y2025/V49/I5/1126

Schematic of EH4 field work arrangement

Stainless steel electrode

Copper electrode

Saturated copper sulfate non-polarized electrode

Solid non-polarized electrodes

The effect of grounding resistance on apparent resistivity

The effect of grounding resistance on impedance phase

Raw measurement apparent resistivity-phase data for different measurement electrodes

Raw measured apparent resistivity-phase data for different grounding resistances

Cross-sectional view of the two-dimensional inversion results of EH4 data of Liangwangshan Tunnel Survey of Fuyi Expressway in Yunnan Province

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