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<p>Large-scale exploitation of coal resources in the middle and upper reaches of the Yellow River basin in China has deteriorated the ecological environment, mainly due to changes in the groundwater environment. Therefore, accurately determining the distribution characteristics of groundwater in this area is important. Transient electromagnetometry (TEM) with a fixed transmitting loop is usually used to ascertain the distribution characteristics of groundwater in this area. However, the offset of this method distorts the noncentral observation data at early times(ypically within 0.15&#xa0;ms after current turn-off), which decreases the accuracy of groundwater exploration in shallow strata. Therefore, this paper proposes a correction method for noncentral data and constructs several geoelectric models, such as uniform and layered geoelectric models, using the geoelectric conditions in the study area. The induced voltage data of the central and noncentral point with different offsets in the transmitting loop were calculated using the finite difference time domain (FDTD) method. The correction coefficients were obtained for uniform and layered strata conditions. The numerical verification results show that the new correction method can effectively eliminate the influence of offsets caused by noncentral point-induced voltage data, especially in the early stage, and better repair the quality of observation data. The layered all-time correction method was used to correct the noncentral point data for field-measured TEM data with a fixed transmitting loop in the study area. Then, resistivity inversion was carried out based on the apparent resistivity formula of the central point and the inversion resistivity profiles from shallow to deep in the study area were obtained. The results reveal the presence of groundwater in the shallow soil and deep sandstone layers. This verifies the reliability of the new correction method, which can provide strong technical support for ecological and environmental restoration of the middle and upper reaches of the Yellow River basin.</p>

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Correcting Transient Electromagnetic Data Measured at Non-Central Locations with a Fixed Transmitting Loop and its use in Groundwater Detection

  • 期刊论文

  • 发表日期：

    2026年2月24日

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  • Xiongwu Hu,
  • Erman Wang,
  • Ying Wang,
  • Hao Yu,
  • Rixin Deng

摘要

Large-scale exploitation of coal resources in the middle and upper reaches of the Yellow River basin in China has deteriorated the ecological environment, mainly due to changes in the groundwater environment. Therefore, accurately determining the distribution characteristics of groundwater in this area is important. Transient electromagnetometry (TEM) with a fixed transmitting loop is usually used to ascertain the distribution characteristics of groundwater in this area. However, the offset of this method distorts the noncentral observation data at early times(ypically within 0.15 ms after current turn-off), which decreases the accuracy of groundwater exploration in shallow strata. Therefore, this paper proposes a correction method for noncentral data and constructs several geoelectric models, such as uniform and layered geoelectric models, using the geoelectric conditions in the study area. The induced voltage data of the central and noncentral point with different offsets in the transmitting loop were calculated using the finite difference time domain (FDTD) method. The correction coefficients were obtained for uniform and layered strata conditions. The numerical verification results show that the new correction method can effectively eliminate the influence of offsets caused by noncentral point-induced voltage data, especially in the early stage, and better repair the quality of observation data. The layered all-time correction method was used to correct the noncentral point data for field-measured TEM data with a fixed transmitting loop in the study area. Then, resistivity inversion was carried out based on the apparent resistivity formula of the central point and the inversion resistivity profiles from shallow to deep in the study area were obtained. The results reveal the presence of groundwater in the shallow soil and deep sandstone layers. This verifies the reliability of the new correction method, which can provide strong technical support for ecological and environmental restoration of the middle and upper reaches of the Yellow River basin.