Quantitative Identification of Near-Fault Pulse-Like Ground Motions Based on Energy

Near-fault pulse-like ground motions have long been known to be capable of inducing significant seismic damages to the building structures. Reasonable classification of such ground motions has been a challenge to earthquake engineers. This study serves to propose an energy-based approach that can be used to identify those ground motions with dominant pulses observed in the velocity time series; and time integral of the squared ground velocity is employed to represent the motion energy. For removing the influence of high-frequency contents, the potential velocity pulse is first extracted with a pulse model. The starting and ending time points as well as period of the velocity pulse are subsequently determined by the peak-point method. Records with peak ground velocities above 30 cm/s from a database containing more than 3600 recorded ground motions are selected and utilized to calibrate the final criterion. It is concluded that those ground motions whose dominant velocity pulses hold relative energy values of greater than 0.3 can be satisfactorily classified as pulse-like. The proposed approach is further used to identify pulse-like features in arbitrary orientations and pulse-like ground motions possibly caused by forward-directivity effects.