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针对地球天然脉冲电磁场信号的非平稳、非线性特点,本文采用基于聚类经验模态分解(EEMD)提取信号时频特性的方法,有效获得了芦山MS7.0地震前地球天然脉冲电磁场信号的时频分布特性、瞬时能量谱、能量集中分布的频段、最大振幅对应的时频分布等特性。对比经验模态分解(EMD)的希尔伯特-黄变换(HHT)方法,EEMD有效抑制了以往EMD分解过程中所出现的模态混叠问题。文章还将EEMD和傅里叶变换、小波变换进行了对比研究。结果表明,对于非平稳的地球天然脉冲电磁场数据,采用EEMD分解的HHT方法更能反映出原始数据的多种固有特性,便于进一步了解地震前地球天然脉冲电磁场的特点。
Aiming at the non-stationary and nonlinear characteristics of Earth’s natural pulsed electromagnetic field signals, this paper adopts the method of extracting the time-frequency characteristics of signals based on clustering empirical mode decomposition (EEMD) to effectively obtain the Earth’s natural pulsed electromagnetic signal before the MS 7.0 Lushan Earthquake Frequency distribution characteristics, instantaneous energy spectrum, energy concentrated distribution of the band, the maximum amplitude corresponding to the time-frequency distribution and other characteristics. In contrast to the Hilbert-Huang transform (HHT) method of Empirical Mode Decomposition (EMD), EEMD effectively suppresses the modal aliasing problems in EMD decomposition. The article also compares EEMD with Fourier transform and wavelet transform. The results show that the HEM method using EEMD decomposition can better reflect the inherent characteristics of the original data for non-stationary Earth’s natural pulsed electromagnetic field data to further understand the characteristics of natural pulsed electromagnetic fields before Earthquakes.