Abstract
It is well known that arbitrary amplitude and phase spectra cannot be assigned to simulate an earthquake motion with causality. We therefore have developed a new method to simulate earthquake motion which can take into account the causality characteristics. In this study we point out that we need to define not only the average and standard deviation of group delay time but also the correlation of group delay time between frequency. We demonstrate that a non-stationary earthquake motion can be synthesized from phase information reasonably by defining the auto correlation function of group delay time as exponential function type.
