Quantitative identification of near-fault pulse-like ground motions based on variational mode decomposition technique

Near-fault ground motions have distinctive features different from typical far-field ground motions. The approach detects near-fault pulse-like ground motion based on the variational mode decomposition (VMD) technique. First, the original ground motion can be decomposed into a series of intrinsic mode functions (IMFs) with the VMD technique. The low-frequency signal is obtained by synthesizing the IMFs with the center frequency lower than an adaptive frequency threshold proposed in this paper. Second, the pulse signal and the pulse period are obtained from the best-fitting low-frequency signal by the peak-point method. Finally, 596 records are utilized to calibrate the classification standard. It is concluded that these ground motions with relative energy indicator greater than 0.27 can be classified as pulse-like. The approach is further used to identify the pulse-like ground motion with a significant velocity pulse at the beginning, which may be caused by the forward-directivity effects.