基于改进HHT的地下洞室爆破地震波信号时频分析

Time-frequency analysis of underground cavern blasting seismic wave signal based on improved HHT

为了找出适合非平稳爆破地震波信号的时频分析算法,进行了短时傅里叶变换(STFT)、连续小波变换(CWT)、离散小波变换(DWT)、希尔伯特-黄变换(HHT)和改进HHT的烟台某地下洞室爆破地震波监测信号时频分析对比研究。分析结果表明:STFT适合平稳信号时频分析,不适合爆破地震波这种非平稳、非线性的信号;CWT可得出特定尺度-位移平面下的小波系数,也引入了冗余成分,导致小波逆变换重构不唯一;DWT能在一定程度描述信号的局部特征,但过度依赖于小波基的选择;HHT依据信号本身的特性进行分解,时频分析结果具有自适应性,但爆破地震波信号多为含噪信号,噪声的存在导致经验模态分解(EMD)产生模态混淆的现象。同时EMD无法免除端点效应的影响,时频分析精度受损。针对以上问题,通过在补充集合经验模态分解(CEEMD)中添加端点处理程序,得到能够同时抑制模态混淆和端点发散的改进HHT算法。改进的HHT算法能够得到物理意义明确的IMF,是一种更优越的时频分析方法,可为地下洞室爆破提供参考。

In order to find a time-frequency analysis algorithm suitable for non-stationary blasting seismic wave signals,a comparative study was conducted on the time-frequency analysis of the monitoring signals of an underground cavern in Yantai using Short-time Fourier Transform(STFT),Continuous Wavelet Transform(CWT),Discrete Wavelet Transform(DWT),Hilbert-Huang Transform(HHT),and improved HHT.The analysis results show that:STFT is suitable for the time-frequency analysis of stationary signals,but not for the non-stationary and nonlinear signals of blasting seismic waves;CWT can obtain wavelet coefficients in a specific scale displacement plane,and redundant components are also introduced,resulting in non unique reconstruction of inverse wavelet transform;DWT can describe the local characteristics of signal to a certain extent,but it depends too much on the selection of wavelet basis;HHT is decomposed according to the characteristics of the signal itself,and the time-frequency analysis results are adaptive.However,the blasting seismic wave signal is mixed with noise in most cases,and the existence of noise leads to the phenomenon of mode confusion in EMD.At the same time,EMD can not avoid the influence of endpoint effect,and the accuracy of time-frequency analysis is damaged.Add endpoint processing to the Complementary Ensemble Empirical Mode Decomposition(CEEMD)to obtain an improved HHT algorithm that can simultaneously suppress modal confusion and endpoint divergence.Therefore,the improved HHT algorithm can obtain IMF with clear physical meaning,which is a more superior time-frequency analysis method,can provide reference for underground chamber blasting.