Earth Science Frontiers ›› 2016, Vol. 23 ›› Issue (1): 275-286.DOI: 10.13745/j.esf.2016.01.025

• Article • Previous Articles    

Timefrequency analysis of the Earths natural pulse electromagnetic field signal before and after the Lushan MS 7.0 earthquake based on NSTFTWVD transform.

  

  • Received:2015-07-28 Revised:2015-11-13 Online:2016-01-15 Published:2016-01-15

Abstract:

The present paper aims at the nonstationary characteristics of Earths natural pulse electromagnetic field (ENPEMF) signals by using the normalized STFT - WVD(NSTFT - WVD) transformation, and the main analysis focuses on timefrequency characteristics of the ENPEMF signal before Lushan MS 7.0 earthquake. By comparing shorttime Fourier transform(STFT)and WignerVille distribution(WVD)transformation with the linear frequency modulation signal, this paper analyzes their advantages and disadvantages of both time and frequency focusing performance. NSTFT - WVD transform method can give us the better timefrequency aggregation and inhibits the cross terms. The results show that NSTFT - WVD transform can reflect the real ENPEMF signal timefrequencyenergy spectrum distribution before and after the earthquake, which could render more obvious silent state in entire frequency and sustained 12 days before the earthquake. The timefrequency representation of data channels 2 and 3 are basically consistent with this characteristic, which well represents the feature of impending earthquake precursors.

Key words: earthquake, the Earths natural pulse electromagnetic fields(ENPEMF), Normalized STFTWVD (NSTFTWVD), crossterm suppression, timefrequency analysis

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