SIMPLIFIED GROUND MOTION PULSES IN THE NEAR-FAULT REGION

Near-fault ground motions with long-period pulse have been identified as critical in the design of structures. To aid in the representation of this special type of motions, 8 simple pulses that characterize the effects of either the fling-step or forward-directivity are considered. Relationships between pulse amplitudes and velocity pulse period for different pulses are discussed. Then, response spectral and Fourier amplitude spectral characteristics for the simple pulses are identified and compared in terms of fixed PGA and PGV, respectively. It is concluded that response spectra and Fourier amplitude spectra are all strongly affected by the duration of pulses and the shape of the basic pulse. These special aspects of pulse waveforms, their elastic response spectra and Fourier amplitude spectra should be well accounted for in the estimation of ground motion pulses for use in engineering studies, in particular when local site effects are considered in the near-fault region