Time-domain denoising of time–frequency electromagnetic data  

时频电磁法勘探数据时域去噪方法研究（英文）

作　　者：Zhang Bi-Ming Dai Shi-Kun Jiang Qi-Yun Yan Jian Li Guang 张必明;戴世坤;蒋奇云;颜剑;李广(湖南工程学院计算机与通信学院,湖南湘潭411104;中南大学地球科学与信息物理学院,长沙410083;有色金属成矿预测与地质环境监测教育部重点实验室(中南大学),长沙410083;中南大学交通运输工程学院,长沙410075)

机构地区：[1]School of Computer and Communication,Hunan Institute of Engineering,Xiangtan,Hunan,411104,China [2]School of Geosciences and Infb-Physics,Central South University,Changsha 410083,China [3]Laboratory of Metallogenic Prediction of Non ferrous Metals and Geological Environment Monitoring(Central South University),Ministry of Education,Changsha 410083,China [4]School of Traffic and Transportation Engineering,Central South University,Changsha 410075,China

出　　处：《Applied Geophysics》2019年第3期378-393,398,共17页应用地球物理（英文版）

基　　金：supported by the National Natural Science Foundation of China(No.41574127 and No.41227803)

摘　　要：Time–frequency electromagnetic data contain frequency and transient electromagnetic information and can be used to determine the apparent resistivity both in the frequency and time domains.The observation data contains three types of noise:the harmonics interference at 50 Hz,high-frequency random noise,and low-frequency noise.We use frequency-domain bandstop filtering to remove the harmonics interference noise,segmentation and extension median filtering,and fitting of fixed extremes in empirical mode decomposition to remove the high-frequency and low-frequency noise,respectively;furthermore,we base the selection of median filtering window size on the variance and skewness coefficient of the data.We first remove the harmonics interference at 50 Hz,then the high-frequency noise,and finally the low-frequency noise.We test the proposed methodology by using theory and experiments,and we find that the three types of noises are removed,the phase and amplitude information of the signal are maintained,and high-quality waveforms are obtained in the time domain.时频电磁法勘探系统兼有频率测深与瞬变电磁测深系统双重特点,可同时在频率域和时间域求取视电阻率,从而获得更加准确可信的地电信息。实测时频电磁勘探数据中的主要噪声有50 Hz工频及其谐波干扰噪声、高频随机脉冲噪声以及低频干扰噪声三种类型,本文针对这些噪声类型以及时频电磁法的方波信号特点,提出分段拓展中值滤波方法和拟合固定极值点EMD方法分别去除高频随机脉冲噪声和低频干扰噪声,提出基于方差和偏度系数的中值滤波窗口大小试验选取方法,采用频域带阻滤波方法去除50 Hz工频及其谐波干扰噪声。并设计了一个相应的去噪流程,以充分发挥各自的去噪方法的优势。经理论分析以及实际观测数据的应用实验验证,本文提出的去噪方法和设计的去噪处理流程合理有效,准确保留了时域信号波形的相位和幅值信息,得到令人满意的高质量时域信号波形,为准确地提取时域瞬变电磁衰减信号打下良好的基础。

关 键 词：ELECTROMAGNETIC DENOISING FILTERING BANDSTOP EMD 

分 类 号：P631.325[天文地球—地质矿产勘探]