TIME-VARYING SPECTRUM ESTIMATION OF EARTHQUAKE GROUND MOTION VIA MODERN TIME-FREQUENCY ANALYSIS

The Problems of estimating the time-varying spectrum of earthquake ground motions estimation using STFT, Wigner-Ville distribution, continuous wavelet transform, S-transform and improved S-transform with a complex window are addressed. Mathematical expression of wavelet energy spectrum based on continuous wavelet transform was derived. Numerical results show that estimating the time-varying spectrum of separable non-stationary ground motion via STFT is effective provided the width of window is chosen properly, however,wavelet transform,S-transform and improved S-transform will lead to energy overlapping in high frequency range. The improved S-transform is found to be most effective to estimate the time-varying spectrum of ground motion with high non-stationariness in frequency by adjusting the parameter of time window.The continuous wavelet transform has effective time-domain resolution even though the energy overlapping in high frequency range.