Time-frequency Analysis of Natural Accelerograms
DOI:
https://doi.org/10.24160/1993-6982-2019-5-135-141Keywords:
evolutionary spectral analysis and spectral power density, seismic intensity, seismic analysis, eismic stability analysis, acceleration time historyAbstract
An example of a frequency-time analysis of a long-period accelerogram of Tohoku earthquake is considered (Tohoku earthquake, Japan, March 11, 2011) including seismic intensity definition as a function of time; evolutionary spectral power density; prevailing frequencies of seismic ground motion for different earthquake phases . The function of seismic intensity is obtained as pseudo-envelope of nonstationary seismic accelerations. The time dependent pseudo-envelope is calculated as standard deviation at small time intervals. The analysis of the time dependent prevailing frequencies is performed using the Welch’s power spectral density estimation smoothed with the Hamming windows. For the considered accelerogram, a decrease in prevailing frequencies from 0.77 Hz at the beginning to 0.38 Hz at the end of seismic motion was determined. All calculations were realized using Matlab.
The results of the research may be useful for performing seismic analysis based on accelerograms using response spectrum method, when it is necessary to estimate seismic intensity. Spectral analysis of different earthquake phases is necessary to prevent resonance phenomena in the situation, for example, when during a long-term earthquake both the natural frequencies of the structure and the prevailing frequency of the impact are reduced. In general, the understanding of the changes in the time-dependent parameters of accelerograms is relevant in the seismic analysis taking duration of the earthquake into account. Such calculation should include a preliminary time-frequency analysis of seismic impact.
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Для цитирования: Позняк Е.В., Радин В.П., Новикова О.В. Частотно-временной анализ акселерограмм природных землетрясений // Вестник МЭИ. 2019. № 5. С. 135—141. DOI: 10.24160/1993-6982-2019-5-135-141.
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For citation: Poznyak E.V., Radin V.P., Novikova O.V. Time-frequency Analysis of Natural Accelerograms. Bulletin of MPEI. 2019;5:135—141. (in Russian). DOI: 10.24160/1993-6982-2019-5-135-141.

