A classification method for pulse-like ground motions based on S-transform

This article presents a new identification procedure to detect pulse-like ground motion based on the S-transform. The S-transform is utilized as an effective tool for time-frequency representation of ground motions. It is shown that plots of the S-transform in the time-frequency domain named as the S-feature provide useful information for initial detection of pulses in the velocity time history of the ground motions. To perfect identification of pulse-like motions, a method is presented for extraction of pulses from original ground motions based on the convolution theorem. The proposed procedure is applied for classification of pulse-like near-fault ground motions owing to directivity effects in a data set of selective earthquakes. The period of velocity pulses, as an important parameter in structural engineering, is also determined from extracted pulses. The results of this study provide a suitable platform for selecting pulse-like records, when seismic analyses of structures in near-fault areas are of primary interest.