Numerical modelling of sub-ionospheric Very Low Frequency radio signal anomalies during the Samos (Greece) earthquake (M = 6.9) on October 30, 2020

Biswas, Sagardweep; Chowdhury, Swati; Sasmal, Sudipta; Politis, Dimitrios Z.; Potirakis, Stelios M.; Hayakawa, Masashi

doi:10.1016/j.asr.2022.06.016

Cited by 11 publications

(8 citation statements)

References 44 publications

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“…In addition, it should be noted that several individual EQs were recorded close to the observed ICV signal propagation path in other areas, but the maximum magnitude of these EQs was only 4.2 (the corresponding event occurred in Bosnia and Herzegovina on 31 October, 2016), which is why their significant impact on the STT shift is not expected. This conclusion is based on previous studies where corresponding changes are recorded for only much stronger earthquakes (see, for example, Hayakawa et al, 1996 andBiswas et al, 2022).…”

Section: Observations and Study Areamentioning

confidence: 55%

“…As mentioned in the Introduction, several studies have analyzed STT in time periods around several EQs. A comparison of the data obtained in this research with the results of two other studies related to EQs that occurred in Kobe, Japan (Hayakawa et al, 1996), and near the Samos island in Greece (Biswas et al, 2022) are given in Table 2. The basic characteristics given in them are the existence of the SRT and SST shift in both days before and after the EQ.…”

Section: Resultsmentioning

confidence: 77%

“…The significant SST shifts are recorded before (toward DT and NT) and after (toward NT) EQ for two and one paths, respectively, and they are not recorded for two paths. The importance of signal selection in corresponding research is also indicated in analysis of the period around the time of EQ that occurred near the Samos island, Greece (30 October, 2020) with magnitude of 6.9 (Biswas et al, 2022).…”

Section: Resultsmentioning

confidence: 99%

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Analysis of the Solar Terminator Shift Determined from the VLF Signal Amplitude in the Period Around the Intense Seismic Activity in Central Italy from 25 October to 3 November 2016

Nina¹,

Biagi²,

Пулинец³

et al. 2022

Serbian Journal of Geosciences

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Lower ionosphere, Earthquakes, VLF signal.Since the middle of the last century, numerous studies indicate the possibility that ionospheric perturbations can be precursors of earthquakes (EQs). At the same time, different types of perturbations related to various ionospheric areas were observed. Among them, shifts in the times of occurrence of minimum amplitudes of very low/low frequency (VLF/LF) signals used for monitoring the lower ionosphere in the sunrise and sunset periods (the so-called Solar terminator time -STT) are shown in several studies. In this paper, we analyse STT of the 20.27 kHz ICV signal emitted in Italy and recorded in Serbia in the period from October 15 to November 13, 2016. This period includes 10 days (October 25 -November 3, 2016) when 981 EQs with the minimum magnitude of 2 out of which 31 had the minimum amplitude of 4 were registered in Central Italy. The obtained results show that the STT shifts during sunrise are predominantly due to seasonal changes, while the additional sudden shifts (most pronounced before and at the beginning of intense seismic activity (PISA) in Central Italy) are observed during sunset.

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Section: Observations and Study Areamentioning

confidence: 55%

Section: Resultsmentioning

confidence: 77%

Section: Resultsmentioning

confidence: 99%

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Analysis of the Solar Terminator Shift Determined from the VLF Signal Amplitude in the Period Around the Intense Seismic Activity in Central Italy from 25 October to 3 November 2016

Nina¹,

Biagi²,

Пулинец³

et al. 2022

Serbian Journal of Geosciences

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“…Furthermore, some studies based on numerical simulation of the diurnal variation of the amplitude of the VLF signal, taking into consideration the characteristics of the VLF propagation path, the transmitter, and the receiver, have been applied for the determination of TTs [Chakraborty et al, 2017;Ghosh et al, 2019;Biswas et al, 2022].…”

Section: Terminator Time Methods (Ttm)mentioning

confidence: 99%

Lower-ionosphere anomalies prior to strong earthquakes that occurred in north-central mainland Greece on March 2021 as revealed by multi-method analysis of VLF sub-ionospheric propagation data

Politis,

Potirakis,

Contoyiannis

et al. 2023

Annals of Geophysics

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In this work we present the multi-method analysis of very low frequency (VLF) data, acquired by the radio receiver with call name UWA, located in Athens (Greece), in the University of West Attica, focusing on two strong ( ) earthquakes (EQs) that occurred in north-central mainland Greece sequentially, on 3 and 4 March 2021, with very close epicenters. Specifically, we used the data acquired from seven VLF transmitters located in Europe, North/North-West to UWA, and their propagation paths include the specific EQs epicenters. We analyzed these data using multiple analysis methods in order to investigate for possible EQ-related anomalies, taking also into account all the other possibly ionosphere-influencing extreme events that occurred during the studied period. Especially, we applied the “nighttime fluctuation method” (NFM), as well as, the “terminator time method” (TTM) in order to reveal any statistical anomaly in the nighttime amplitude recordings of VLF sub-ionospheric propagation data within 15 days before each one examined EQs. Also, we calculated the scalogram (wavelet power spectrum over time) using Morlet mother wavelet of the same nighttime data searching for possible imprints of wave-like structures during the same time period. In terms of criticality analysis, first we applied the “natural time” (NT) analysis method to the daily-valued NFM VLF propagation quantities, and subsequently applied the “method of critical fluctuations” (MCF) to the raw nighttime amplitude VLF recordings, to check for any criticality signatures up to two weeks before the examined EQs. Taking into account all the above-mentioned analysis results, we conclude that there are multiple indications that the lower ionosphere was indeed disturbed due to the preparation processes of the above-mentioned EQs, offering different types of seismogenic indications.

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“…Thus, this particle burst can be treated as significant indirect evidence of the seismogenic anomalies in the upper atmosphere. In the upper atmosphere, ionospheric variabilities during and before EQs can be well estimated through Pre-seismic anomalies in multi-parameters the sub-ionospheric VLF radio-sounding techniques [Chakrabarti et al, 2005;Chakrabarti et al, 2007;Sasmal et al, 2009;Chakrabarti et al, 2010;Chakraborty et al, 2017;Biswas et al, 2022;Biswas et al, 2023;Ghosh et al, 2019;Pal et al, 2017;Maurya et al, 2016;Nina et al, 2021;Politis et al, 2021;Potirakis et al, 2018a;Ray et al, 2010;Ray et al, 2011;Ray et al, 2012;Sasmal et al, 2010;Sasmal et al, 2014;Yoshida et al, 2008;Rozhnoi et al, 2014a;Rozhnoi et al, 2013;Popov et al, 2004]. Another important parameter is the F-layer's critical frequency, which shows significant anomalies before the EQs [Ghosh et al, 2017].…”

Section: Introductionmentioning

confidence: 99%

Multi-parametric study of seismogenic anomalies during the 2021 Crete earthquake (M=6.0)

Sasmal,

Chowdhury,

Kundu

et al. 2023

Annals of Geophysics

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It is well established that pre- and co-seismic irregularities in the earth’s atmosphere highly depend on a set of parameters. According to the Lithosphere-Atmosphere-Ionosphere Coupling (LAIC) mechanism, these parameters are associated with various channels (thermal, chemical, acoustic, electromagnetic, etc.) through which an earthquake (EQ) preparation process can have its anomalous phenomena. In this research, we perform a multi-parametric observation using various channels during a strong EQ (M = 6.0) on September 27, 2021, on Crete Island in Greece. We investigate the acoustic and electromagnetic channel using ground and satellite-based observation. We present the Atmospheric Gravity Wave (AGW) in the acoustic channel using the temperature profile computed from the SABER/TIMED instrument. In the electromagnetic channel, ionospheric Total Electron Content (TEC) is recorded by the GNSS-IGS station DYNG in Greece. This TEC information is also used in the acoustic channel anomaly by computing the wave-like structures in the small-scale fluctuation of the TEC profile. We compute energetic (30 to 100 keV) electron precipitation in the inner radiation belt from the NOAA satellite. We also investigate the outcomes of the SWARM satellite to compute the magnetic field and electron density profile. All the parameters show significant seismogenic anomalies (mostly enhancement) before the EQ. To understand each parameter’s temporal and spatial sensitivity, we present a comparison using the anomalies in each parameter.

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Numerical modelling of sub-ionospheric Very Low Frequency radio signal anomalies during the Samos (Greece) earthquake (M = 6.9) on October 30, 2020

Cited by 11 publications

References 44 publications

Analysis of the Solar Terminator Shift Determined from the VLF Signal Amplitude in the Period Around the Intense Seismic Activity in Central Italy from 25 October to 3 November 2016

Analysis of the Solar Terminator Shift Determined from the VLF Signal Amplitude in the Period Around the Intense Seismic Activity in Central Italy from 25 October to 3 November 2016

Lower-ionosphere anomalies prior to strong earthquakes that occurred in north-central mainland Greece on March 2021 as revealed by multi-method analysis of VLF sub-ionospheric propagation data

Multi-parametric study of seismogenic anomalies during the 2021 Crete earthquake (M=6.0)

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Numerical modelling of sub-ionospheric Very Low Frequency radio signal anomalies during the Samos (Greece) earthquake (M = 6.9) on October 30, 2020

Cited by 11 publications

References 44 publications

Analysis of the Solar Terminator Shift Determined from the VLF Signal Amplitude in the Period Around the Intense Seismic Activity in Central Italy from 25 October to 3 November 2016

Analysis of the Solar Terminator Shift Determined from the VLF Signal Amplitude in the Period Around the Intense Seismic Activity in Central Italy from 25 October to 3 November 2016

Lower-ionosphere anomalies prior to strong earthquakes that occurred in north-central mainland Greece on March 2021 as revealed by multi-method analysis of VLF sub-ionospheric propagation data

Multi-parametric study of seismogenic anomalies during the 2021 Crete earthquake (M=6.0)

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Numerical modelling of sub-ionospheric Very Low Frequency radio signal anomalies during the Samos (Greece) earthquake (M = 6.9) on October 30, 2020