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Time-Frequency Decomposition of Seismic Signals Based on Short Time Fourier Transform

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Author(s): Vidosav Stojanović | Miomir Stanković | Igor Radovanović

Journal: Facta Universitatis Series : Electronics and Energetics
ISSN 0353-3670

Volume: 12;
Issue: 2;
Start page: 209;
Date: 1999;
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Keywords: Short time Fourier analysis (STFT) | time frequency analysis | seismic signals

ABSTRACT
The squared module of short-time Fourier transform (STFT) called spectrogram (SPEC) is used for decomposing the seismic signal energy into the time-frequency (TF) plane. The SPEC is calculated by using a window function which width is determined by duration of the excitation signal. The seismic signal energy distribution is observed and the definition of the energy center frequency is given. After making a number of experiments with the seismic signals obtained from the hit of the metal sphere against the lawn, both the mean value of the energy center frequency and the standard deviation are found and given in terms of the distance between the detector and the place of excitation. Both functions decrease as distance increases, so it is possible to estimate the distance using only one detector. These results are useful for seismic signal analysis when several excitations occur. This is demonstrated in the analysis of seismic signals obtained from two sphere excitations. A signal obtained from a car is also analyzed. It is presented that the seismic signal energy center frequency obtained from the car excitation occurs at frequencies higher than those obtained from the sphere. Accordingly, the car and the metal sphere identification, when both excitations occur at the same time, is made.
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