Abstract
The paper is devoted to the analysis of frequency spectra and pulse waveform variety of the geoacoustic and electromagnetic signals recorded on Kamchatka Peninsula at “Karymshina” site during seismically calm and active periods. Signal pre-processing includes pulse detection and their waveforms reconstruction. A frequency spectrum is analyzed using the Adaptive Matching Pursuit algorithm. To study a variety of waveforms, each pulse is encoded by a special descriptive matrix. Then pulse classification based on similarity of the descriptive matrices is performed. Thus, a signal alphabet is formed. The authors analyzed the geophysical signals recorded before, during and after the earthquake with the magnitude Mw = 7.5 dated March 25, 2020. The obtained estimates of frequency spectra and signal alphabets are compared with the analysis results of signal recoded during the seismically calm period of March 22, 2020.
Highlights
The results of earlier studies [1,2,3] show presence of a pre-seismic response in geoacoustic emission and VLF electromagnetic radiation signals. This response is a characteristic change in a signal frequency [4]
Fifteen-minute records of geoacoustic signals were processed and analyzed (16 records made under good weather conditions during the seismically calm period on March 22, 2020; 5 records made in the time interval ±30 minutes near the earthquake registered on March 25, 2020 at 02:49:21 UTC). fifteen-minute records of electromagnetic signals were processed and analyzed (17 records made under good weather conditions during the seismically calm period; 5 records made in the time interval ±30 minutes near the earthquake)
The presented work is devoted to complex analysis of the background, pre- and postseismic pulse signals of geoacoustic emission and VLF electromagnetic radiation
Summary
The results of earlier studies [1,2,3] show presence of a pre-seismic response in geoacoustic emission and VLF electromagnetic radiation signals. In some cases, this response is a characteristic change in a signal frequency [4]. According to the Earthquakes Catalogue for Kamchatka and the Commander Islands (1962 – present) provided by KB GS RAS the earthquake local magnitude ML is 7.7 (http://sdis.emsd.ru/info/earthquakes/catalogue.php). This is one of the strongest regional earthquakes in the last 20 years
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