EMD方法在强震记录处理中的应用研究

Study on EMD method in strong motion record processing application

本文选取"5·12"汶川地震强震记录,利用希尔伯特-黄变换(HHT)中的经验模态分解(EMD),研究EMD对加零数据的敏感性,人为生成时程、各模态速度和位移的特点,各固有模态(IMF)的对称性,研究表明:(1)数据加零会影响IMF首尾波形;(2)利用上下包线提取IMF可能会引入噪声;(3)各IMF的位移和速度存在严重的漂移,EMD方法是一种非线性操作;(4)各IMF倾向于对称;(5)EMD方法需要与滤波器联合使用才能得到合理的速度和位移时程。

This article selects the strong motion record of the ＂5 · 12＂ Wenchuan earthquake and uses the empiri- cal mode decomposition （EMD） in the Hilbert-Huang Transform （HHT） in studying the sensitivity to zero pad- ding, creation of artificial time-history features, characteristics of velocity and displacement of each mode, and tend- ency to produce ＂symmetrical＂ mode of the intrinsic mode function （IMF）. The result shows that： （1） zero pad- ding of the data will affect both ends waveform of the IMF ; （2） by extraction of upper and lower envelope of IMF, the noise will be introduced possibly; （3） there exits serious drift in the velocity and the displacement of each of the IMFs, and the EMD is a nonlinear operation; （4） each of the IMF tends to be symmetrical; （5） the EMD method needs to be used in conjunction with filter so as to get reasonable velocity and displacement time history.