GENERATION OF FULLY NONSTATIONARY GROUND MOTIONS BASED ON PHASE DIFFERENCE SPECTRUM

摘要

A method of generating nonstationary ground motions accounting for the time-variation of intensity and frequency contents, typical of real earthquake ground motions, is formulated and validated. The factors influencing the nonstationarity of earthquake ground motions in time and frequency domains are studied using the multiple-window method. It is shown that the nonstationarity is mainly controlled by the probability distribution of the phase difference spectrum, defined by Ohsaki. The probability distribution model of the phase difference spectrum is ascertained using estimation testing. The method of generating ground motions nonstationary both in time and frequency domains is established based on the empirical relations of the statistical characteristics of phase difference spectrum to earthquake parameters, such as the magnitude and the epicenter distance. Numerical examples show that artificial ground motions possess the time and frequency nonstationarity.