A method to extract successive velocity pulses governing structural response from long-period ground motion

A series of relatively long-period velocity pulses appearing in the later part of ground motion, which is the characterization of far-source long-period ground motions in basin (“long-period ground motion” for short), is mainly influenced by focal mechanism, basin effect, and dispersion. It was supposed that the successive low-frequency velocity pulses in long-period ground motion caused the resonance of long-period structures in basin, which are of special concern to designers of super high-rise buildings. The authors proposed a wavelet-based successive frequency-dependent pulse extraction (WSFPE) method to identify and extract these pulses with dominant period of interest from long-period ground motions. The pulses extracted by using two frequently used methods (zero-crossing analysis, empirical mode decomposition) were compared to the pulses extracted by using WSFPE. The results demonstrate that the WSFPE provides higher resolution in time–frequency domain than the other two methods do. The velocity pulses extracted by using WSFPE are responsible for the resonance and maximum response of structure subjected to long-period ground motions. WSFPE can be used to make a better understanding of long-period ground motions and to promote the formation of long-period ground motion model which will help the seismic design of long-period structures built in sedimentary basin.