Spectral Estimation of Noisy Seismogram using Time-Frequency Analyses

Spectral Estimation of Noisy Seismogram using Time-Frequency Analyses

Vaneeta Devi (IIT Roorkee, Roorkee, India) and M. L. Sharma (IIT Roorkee, Roorkee, India)
Copyright: © 2016 |Pages: 14
DOI: 10.4018/IJGEE.2016010102
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Time–Frequency analyses have the advantage of explaining the signal features in both time domain and frequency domain. This paper explores the performance of Time–Frequency analyses on noisy seismograms acquired from seismically active region in NW Himalayan. The Short Term Fourier Transform, Gabor Transform, Wavelet Transform and Wigner-Ville Distribution have been used in the present study to carry out Time-Frequency analyses. Parametric study has been carried out by varying basic parameters viz. sampling, window size and types. Wavelet analysis (Continuous Wavelet Transform) has been studied with different type of wavelets. The seismograms have been stacked in time-frequency domain using Gabor Transform and have been converted using Discrete Gabor Expansion techniques. The Spectrograms reveals better spectral estimation in time-frequency domain than Fourier Transform and hence recommended to estimate dominate frequency components, phase marking and timings of phase. The time of occurrence of frequency component corresponding to maximum energy burst can be identified on seismograms
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Time-Frequency Analysis (Tfa) Techniques

Signal processing techniques are classified as time domain, frequency domain, and time-frequency domain methods. These methods are complementary to each other and selection of suitable technique for specific objectives in observational seismology becomes a challenging task. Therefore, some of the widely used time-frequency domain signals processing techniques have been revisited with respect to seismic signal processing needs and are discussed in this paper to find out their suitability in specific cases. Moreover, time-frequency analysis can give interesting information with regards to energy distribution over frequency bands. A number of techniques of time-frequency analysis, such as the Short Time Fourier Transform, Wavelet Transforms, and Wigner-Ville Distribution have been used for frequency estimation in non-stationary seismic signals obtained from an active seismic region in Himalayas through deployment of short network of short period seismographs.

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