Wavelet-Based Stochastic Simulation of Pulse-Like Vertical Motions for Specified Seismic Source and Site Condition

ABSTRACT The vertical component of ground motion has been shown to cause significant structural damage in past earthquakes. For near-fault ground motions, the vertical component may also exhibit pulse-like properties, which have been rarely studied. In our study, we propose a method to generate pulse-like vertical motions in the near-fault region. Our method employs wavelet packets to characterize and model the dominant pulse in velocity time histories. Predictive equations are developed for the model parameters in terms of seismic source parameters and site conditions. We also estimate correlation structures by analyzing the regression residuals, and systematically compare our simulation results with existing ground-motion models (GMMs). Furthermore, an attempt is made to simulate pulse-like horizontal and vertical components simultaneously. The correlation coefficients of model parameters are estimated based on a subset of the entire database in which both horizontal and vertical components exhibit pulse-like properties. We then compare vertical-to-horizontal spectral ratios of our simulations with empirical GMMs. The proposed method has applications in multicomponent analysis of earthquake response in the near-fault region.