Time-frequency analysis and artificial simulation of earthquake ground motions via S-transform

The formulas of discrete S-transform are derived,and the time-varying amplitude spectrum and time varying energy spectrum based on S-transform are given.The time-varying energy spectrum of Kobe wave is estimated by using S-transform with different window function,numerical results show that the improved Stransform is the effective method when choosing the time window parameter properly.Earthquake records can be adjusted with time-frequency filtering based on Stransform,and a new procedure is presented to generate an accelerograms whose power spectrum is compatible with a target spectrum by using actual earthquake records as parents.It is showed that the power spectrums of reconstructed accelerograms have good matching with the target spectrum and preserve the non-stationary features of the parents accelerograms.Finally,the effects of the non-stationary frequency characteristic of ground motions on the response spectrum are investigated.