Abstract: The Hilbert spectra of frequency-time-amplitude can beobtained by HHT and be applied to dynamic analysis of the seismicsignal. A quantitative index to evaluate strengthof vibration effect by the use of the maximum energy (integralof the time-domain frequency density function) and the crest factor ofearthquake wave are put forword, as a preliminary unified criterion ofvibration effect, and the feasibility and reliability of thecriterion are validated by several instances.