Reduction of the VLF Signal Phase Noise Before Earthquakes
In this paper we analyse temporal variations of the phase of a very low frequency (VLF) signal, used for the lower ionosphere monitoring, in periods around four earthquakes (EQs) with magnitude greater than 4. We provide two analyses in time and frequency domains. First, we analyse time evolution of...
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| Format: | Article |
| Language: | English |
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MDPI AG
2021-03-01
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| Series: | Atmosphere |
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| Online Access: | https://www.mdpi.com/2073-4433/12/4/444 |
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| author | Aleksandra Nina Pier Francesco Biagi Srđan T. Mitrović Sergey Pulinets Giovanni Nico Milan Radovanović Luka Č. Popović |
| author_facet | Aleksandra Nina Pier Francesco Biagi Srđan T. Mitrović Sergey Pulinets Giovanni Nico Milan Radovanović Luka Č. Popović |
| author_sort | Aleksandra Nina |
| collection | DOAJ |
| description | In this paper we analyse temporal variations of the phase of a very low frequency (VLF) signal, used for the lower ionosphere monitoring, in periods around four earthquakes (EQs) with magnitude greater than 4. We provide two analyses in time and frequency domains. First, we analyse time evolution of the phase noise. And second, we examine variations of the frequency spectrum using Fast Fourier Transform (FFT) in order to detect hydrodynamic wave excitations and attenuations. This study follows a previous investigation which indicated the noise amplitude reduction, and excitations and attenuations of the hydrodynamic waves less than one hour before the considered EQ events as a new potential ionospheric precursors of earthquakes. We analyse the phase of the ICV VLF transmitter signal emitted in Italy recorded in Serbia in time periods around four earthquakes occurred on 3, 4 and 9 November 2010 which are the most intensive earthquakes analysed in the previous study. The obtained results indicate very similar changes in the noise of phase and amplitude, and show an agreement in recorded acoustic wave excitations. However, properties in the obtained wave attenuation characteristics are different for these two signal parameters. |
| first_indexed | 2024-03-10T12:44:59Z |
| format | Article |
| id | doaj.art-e3457e3aa65d43f19bd9861bae266e30 |
| institution | Directory Open Access Journal |
| issn | 2073-4433 |
| language | English |
| last_indexed | 2024-03-10T12:44:59Z |
| publishDate | 2021-03-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Atmosphere |
| spelling | doaj.art-e3457e3aa65d43f19bd9861bae266e302023-11-21T13:36:03ZengMDPI AGAtmosphere2073-44332021-03-0112444410.3390/atmos12040444Reduction of the VLF Signal Phase Noise Before EarthquakesAleksandra Nina0Pier Francesco Biagi1Srđan T. Mitrović2Sergey Pulinets3Giovanni Nico4Milan Radovanović5Luka Č. Popović6Institute of Physics Belgrade, University of Belgrade, 11080 Belgrade, SerbiaPhysics Department, Università di Bari, 70125 Bari, ItalyNovelic, 11000 Belgrade, SerbiaSpace Research Institute, Russian Academy of Sciences, 117997 Moscow, RussiaIstituto per le Applicazioni del Calcolo (IAC), Consiglio Nazionale delle Ricerche (CNR), 70126 Bari, ItalyGeographical Institute “Jovan Cvijić” SASA, 11000 Belgrade, SerbiaAstronomical Observatory, 11060 Belgrade, SerbiaIn this paper we analyse temporal variations of the phase of a very low frequency (VLF) signal, used for the lower ionosphere monitoring, in periods around four earthquakes (EQs) with magnitude greater than 4. We provide two analyses in time and frequency domains. First, we analyse time evolution of the phase noise. And second, we examine variations of the frequency spectrum using Fast Fourier Transform (FFT) in order to detect hydrodynamic wave excitations and attenuations. This study follows a previous investigation which indicated the noise amplitude reduction, and excitations and attenuations of the hydrodynamic waves less than one hour before the considered EQ events as a new potential ionospheric precursors of earthquakes. We analyse the phase of the ICV VLF transmitter signal emitted in Italy recorded in Serbia in time periods around four earthquakes occurred on 3, 4 and 9 November 2010 which are the most intensive earthquakes analysed in the previous study. The obtained results indicate very similar changes in the noise of phase and amplitude, and show an agreement in recorded acoustic wave excitations. However, properties in the obtained wave attenuation characteristics are different for these two signal parameters.https://www.mdpi.com/2073-4433/12/4/444ionosphereearthquakesobservationsVLF signalsignal processingacoustic and gravity waves |
| spellingShingle | Aleksandra Nina Pier Francesco Biagi Srđan T. Mitrović Sergey Pulinets Giovanni Nico Milan Radovanović Luka Č. Popović Reduction of the VLF Signal Phase Noise Before Earthquakes Atmosphere ionosphere earthquakes observations VLF signal signal processing acoustic and gravity waves |
| title | Reduction of the VLF Signal Phase Noise Before Earthquakes |
| title_full | Reduction of the VLF Signal Phase Noise Before Earthquakes |
| title_fullStr | Reduction of the VLF Signal Phase Noise Before Earthquakes |
| title_full_unstemmed | Reduction of the VLF Signal Phase Noise Before Earthquakes |
| title_short | Reduction of the VLF Signal Phase Noise Before Earthquakes |
| title_sort | reduction of the vlf signal phase noise before earthquakes |
| topic | ionosphere earthquakes observations VLF signal signal processing acoustic and gravity waves |
| url | https://www.mdpi.com/2073-4433/12/4/444 |
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