基于多频电磁技术的吉林市温德河泥沙分布
Sediment distribution of Wende River in Jilin City based on multi-frequency electromagnetic technology
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摘要: 河流泥沙具有灾害性与资源性双重属性, 如何趋利避害是当前实践层面需要重点探索的关键问题。运用地球物理学方法对河流泥沙分布情况进行高效探查是解决上述问题的一种重要手段。以吉林市温德河流域河道泥沙为主要研究对象, 基于电法勘探对低阻异常区高度敏感的特点, 采用GEM-2多频电磁仪的5个频率(425 Hz、1 475 Hz、5 175 Hz、24 075 Hz、63 025 Hz), 平均线距为60 m, 进行长约20 km的河道泥沙电磁测量, 并结合后期数据处理结果, 圈定了泥沙的平面位置及深度分布范围。研究结果表明: GEM-2多频电磁仪可有效探测河流泥沙分布情况, 泥沙分层界线较为清晰。根据视电导率等值线图, 并结合测线视电阻率-深度反演图, 推断沙层可能分别分布在水面以下2 m、6 m和10 m深度处, 分别对应GEM-2仪器的高频63 025 Hz、中频5 175 Hz和低频425 Hz所对应的探测深度。研究成果可为今后类似问题的勘探和研究提供理论及实践基础。Abstract: River sediment has dual properties of disaster and resource. How to seek advantages and avoid disadvantages is a key problem during practical process. Using geophysical method to efficiently detect the distribution of river sediment is an important mean to solve problems above. The river sediment of Wende River in Jilin city was taken as the main research object, and GEM-2 multi-frequency electromagnetic instrument was used to carry out the electromagnetic measurement of river sediment with a length of about 20 km at five frequencies of 425 Hz, 1 475 Hz, 5 175 Hz, 24 075 Hz, and 63 025 Hz, and an average line spacing of 60 m, based on the high sensitivity of electric exploration to low resistivity anomalies. The plane position and depth range of the river sediment were defined based on post-processing data. The results show that multi-frequency electromagnetic instrument GEM-2 can effectively detect the distribution of river sediment, and the boundary of sediment stratification is relatively clear. Based on the apparent conductivity contour map and the apparent resistivity-depth inversion map of the survey line, it could be inferred that the sand layer may be distributed at a depth of 2 m, 6 m and 10 m below the water surface respectively, corresponding to the detection depths of high-frequency 63 025 Hz and mid-frequency 5 175 Hz and low-frequency 425 Hz of GEM-2 instrument. The results obtained could provide theoretical and practical basis for similar exploration and research in future.
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