A statistical model for phase difference spectrum of ground-motion and its application in generating non-stationary seismic waves

The intensity non-stationarity is one of the most important features of earthquake records. Modeling of this feature is significant to the generation of artificial earthquake waves. Based on the theory of phase difference spectrum, an intensity non-stationary envelope function with log-normal form is proposed. Through a tremendous amount of earthquake records downloaded on Kik-net, a parameter fitting procedure using the genetic algorithm is conducted to obtain the value of model parameters under different magnitudes, epicenter distances and site conditions. A numerical example is presented to describe the procedure of generating fully non-stationary ground motions via spectral representation, and the mean EPSD (evolutionary power spectral density) of simulated waves is proved to agree well with the target EPSD. The results show that the proposed model is capable of describing the intensity non-stationary features of ground motions, and it can be used in structural anti-seismic analysis and ground motion simulation.