A stochastic model and synthesis for near-fault impulsive ground motions

The orientations of ground motions are paramount when the pulse-like motions and their unfavorable seismic responses are considered. This paper addresses the stochastic modeling and synthesizing of near-fault impulsive ground motions with forward directivity effect taking the orientation of the strongest pulses into account. First, a statistical parametric analysis of velocity time histories in the orientation of the strongest pulse with a specified magnitude and various fault distances is performed. A new stochastic model is established consisting of a velocity pulse model with random parameters and a stochastic approach to synthesize high-frequency velocity time history. The high-frequency velocity history is achieved by integrating a stochastic high-frequency accelerogram, which is generated via the modified K-T spectrum of residual acceleration histories and then modulated by the specific envelope function. Next, the associated parameters of pulse model, envelope function, and power spectral density are estimated by the least-square fitting. Some chosen parameters in the stochastic model of near-fault motions based on correlation analysis are regarded as random variables, which are validated to follow the normal or lognormal distribution. Moreover, the number theoretical method is suggested to select efficiently representative points, for generating artificial near-fault impulsive ground motions with the feature of the strongest pulse, which can be used to the seismic response and reliability analysis of critical structures conveniently. Finally, the simulated ground motions demonstrate that the synthetic ground motions generated by the proposed stochastic model can represent the impulsive characteristic of near-fault ground motions. Copyright (c) 2014 John Wiley & Sons, Ltd.