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大地电磁测深采集的是天然电磁场,具有振幅微弱、频带宽的特点.在人文活动密集地区,电磁噪声干扰日趋严重,导致大地电磁测深曲线具有明显的近场源效应.本文利用电偶极子理论模型分析了电磁相关噪声对大地电磁测深数据的影响特征,并对湖南衡阳某矿区噪声实验数据进行了讨论,分析了矿区噪声的特点.分别利用远参考方法和基于大地电磁时间序列依赖关系的去噪方法对实验数据进行了处理.研究结果表明:矿区近场源噪声的频率一般大于0.1 Hz,远参考方法可以压制高频部分近场源噪声,但在0.1 Hz附近仍存在跳点;基于大地电磁时间序列依赖关系的去噪方法也可以压制矿区强相关噪声,抑制近场源效应,其效果要好于远参考的处理;两种方法结合可以更好的压制强噪声,基本消除了近场源效应,有效提高了大地电磁测深数据的信噪比.
The electromagnetic field collected by the earth electromagnetic sounding has the characteristics of weak amplitude and wide frequency band.In the densely populated area of human activities, the electromagnetic noise is becoming more and more serious, which leads to obvious near-field source effect in the earth’s electromagnetic sounding curve.In this paper, The sub-theoretical model analyzes the characteristics of the electromagnetic correlation noise on the electromagnetic data of the earth and discusses the experimental data of the noise in a mining area in Hengyang, Hunan Province, and analyzes the characteristics of the noise in the mining area.Using the far reference method and the time-dependent electromagnetic induction The results show that the frequency of near-field source noise in mining area is generally greater than 0.1 Hz, and the far-reference method can suppress near-field source noise in high frequency part, but there is still a jump point near 0.1 Hz ; The denoising method based on the time series dependence of the earth magnetism can also suppress the strong correlation noise in the mining area and suppress the near-field source effect, and the effect is better than the far reference processing. Combining the two methods can suppress the strong noise better and basically eliminate Near-field source effect, effectively improve the signal to noise ratio of the earth electromagnetic sounding data.