利用Hilbert-Huang变换提取地震信号瞬时参数

Using Hilbert-Huang transform to pick up instantaneous parameters of seismic signal

通过Hilbert变换求取的信号瞬时参数并非对任何信号都有物理意义,此法通常要求被分析信号是窄带或平稳的,而且对噪声很敏感。而实际地震信号既非平稳又含有噪声,若在实际应用中不加考虑地对地震信号进行Hilbert变换以求取瞬时参数,这种情况下求取的瞬时参数将缺乏物理意义甚至失真。Hilbert-Huang变换是一种新的分析非平稳非线性信号的方法,它先将信号进行经验模态分解(EMD),形成有限个固有模态函数(IMF)之和,再对固有模态函数作Hilbert变换求取时频谱,求取的时频谱在时域和频域都具有较高的分辨率。本文将Hilbert-Huang变换应用于地震瞬时参数的提取,实例表明,对地震剖面做EMD可以得到不同时间尺度上的特征,Hilbert谱比传统的时频谱在时间和频率域上的分辨率都要高,强反射层在第1阶IMF瞬时频率剖面上比原瞬时频率剖面上表现得更为明显。

There are physical meanings for taking instantaneous parameters of signal by Hilbert transform, which is not always true for any signals. This approach requires analyzed signals being narrow band or stationary and sensitive to noises. But the practical seismic signals are non-stationary and noisy, if taking instantaneous parameters by Hilbert transform without consideration in practical application, the yielded instantaneous parameters will be lack of physical meanings or distortion. Hilbert-Huang transform is new approach for analyzing non-stationary and non-linear signals, which first carries out empirical mode decomposition (EMD) for signals, forming sum of limited intrinsic mode functions (IMF), then, the time-frequency spectrum is taken for IMF by Hilbert transform, the yielded time-frequency spectrum has higher resolution in both time and frequency domains. The paper applied Hilbert-Huang transform to take seismic instantaneous parameters, which showed in real cases that feature in different time scale could be obtained by carrying out EMD for seismic sections, and Hilbert spectrum has higher resolution in both time and frequency domains in comparison with traditional time-frequency spectrum; the strong reflection horizons appear more distinctive in first-order IMF instantaneous frequency section than in original instantaneous frequency section.