A STUDY ON A GENERATION OF SIMULATED EARTHQUAKE GROUND MOTION CONSIDERING PHASE DIFFERENCE CHARACTERISTICS : Part 1 Theoretical background of the relationship between phase difference distribution and envelope characteristics

Abstract

The purpose of this paper is to demonstrate that the theoretical background of the similarity between the distribution of phase differences and the shape of the wave envelope can be clearly explained by using the concept of beat. The validity of this idea is verified by analyzing recorded earthquake motions. This idea, moreover, derives two significant results, that a wave with uniform phase differences becomes a pulse independently of Fourier amplitude, and that the position of the pulse on the time axis and the pulse type can be specified by the parameters of the phase difference and the initial phase angle. Comparing response spectra of two waves with identical Fourier amplitudes, it is illustrated that the response spectrum depends on Fourier phase as well as Fourier amplitude.