摘要
大地电磁信号中的长周期噪声主要存在于信号的低频、甚低频分段,此类噪声幅值大、随机性强,能将有效的电磁信号完全淹没,导致低频段反演结果出现严重的偏差,为了有效去除大地电磁信号中的长周期噪声,结合变分模态分解(Variational Mode Decomposition,VMD)和多分辨分析的特点,提出了多分辨VMD算法:首先对信号的低频本征模态分量(Intrinsic Mode Function,IMF)进行多层VMD处理,提高长周期噪声在信号低频、甚低频分段的时频分辨率;之后根据噪声的时频特性准确地筛选出包含长周期噪声的IMF分量;最后剔除掉这些IMF分量,达到去除长周期噪声的目的。使用此算法分别对仿真和实测的大地电磁信号进行处理,结果表明:多分辨VMD算法显著的提高了长周期噪声的时频分辨率,通过此算法能够有效的去除大地电磁信号中的长周期方波、三角波噪声,去噪后时域波形的周期性和平滑性明显提高,同时保存了信号的低频有效分量,低频分段的视电阻率、相位图曲线得到了明显优化。
The long-period noise in magnetotelluric signals mainly exists in the low-frequency and very low-frequency segments of the sig⁃nal.This type of noise has large amplitude and strong randomness,which can completely submerge the effective electromagnetic signal and cause serious deviations in the low-frequency inversion results.In order to effectively remove the long-period noise in the magnetotelluric signal,this paper combines the characteristics of Variational Mode Decomposition(VMD)and multi-resolution analysis,and proposes a multi-resolution VMD algorithm:first,perform multi-layer VMD processing on the low-frequency Intrinsic Mode Function(IMF)of the signal to improve the time-frequency resolution of the low-frequency and very low-frequency segments;then according to the time-fre⁃quency characteristics of the noise,the IMF components containing long-period noise are accurately selected;and finally removed these IMF components achieve the purpose of removing long-period noise.Using this algorithm to process the simulated and measured magneto⁃telluric signals separately,the results show that:the multi-resolution VMD algorithm can significantly improve the time-frequency resolu⁃tion of long-period noise,and this algorithm can effectively remove the long-period side of the magnetotelluric signal.Wave and triangle wave noise,the periodicity and smoothness of the time-domain waveform after denoising are significantly improved,while the low-frequency effective components of the signal are preserved,and the apparent resistivity and phase diagram curves of the low-frequency seg⁃ment have been significantly optimized.
作者
庞曦
王晨晨
孙伟翔
PANG Xi;WANG Chenchen;SUN Weixiang(Chengjiao Coal Mine,Yongcheng Coal and Electric Holding Group Co.,Ltd.,Yongcheng 476600,China;Xinqiao Coal Mine,Yongcheng Coal and Electric Holding Group Co.,Ltd.,Yongcheng 476600,China;East China Langyashan Pumped Storage Co.,Ltd.,Chuzhou 239000,China)
出处
《煤炭科学技术》
CAS
CSCD
北大核心
2021年第5期227-233,共7页
Coal Science and Technology
基金
国家科技重大专项资助项目(2016YFC0600906)。
关键词
大地电磁信号
变分模态分解
多分辨分析
长周期噪声压制
magnetotelluric signal
Variational Mode Decomposition
multiresolution analysis
long-period noise suppression
