scholarly journals Lower Ionospheric turbulence variations during the intense tectonic activity in Eastern Aegean area

2020 ◽  
Vol 63 (5) ◽  
Author(s):  
Emmanuel Scordilis ◽  
Michael Contadakis ◽  
Filippos Vallianatos ◽  
Spiridon Spatalas
Keyword(s):  
High Frequency ◽  
Lower Ionosphere ◽  
Earthquake Hazard ◽  
Tectonic Activity ◽  
Ionospheric Turbulence ◽  
Frequency Limit ◽  
Total Electron ◽  
Aegean Area ◽  
Eastern Aegean ◽  
Global Positioning

This paper may be considered as an additional approval of the way the tectonic activity affects the lower Ionosphere. The results of our investigation, on the occasion of the recent East Aegean tectonic activity, indicate that the High - Frequency limit, fo, of the ionospheric turbulence content, increases as the site and the time of the earthquake occurrence is approaching, pointing to the earthquake location.We conclude that the Lithosphere Atmosphere Ionosphere Coupling (LAIC) mechanism through acoustic or gravity wave could explain this phenomenology, as a result of a the frequency differential damping of the propagating turbulent in the ionosphere. Proper use of this result may lead to a method of earthquake hazard mitigation using the byproducts of the Global Positioning Network (actually Total Electron Contain, TEC, estimations) which are available freely.

Lower Ionospheric turbulence variations during the tectonic activity of the last quarter of 2019 in the Hellenic Arc (Greece)

2020 ◽  
Author(s):  
Dimitrios N. Arabelos ◽  
Michael E. Contadakis ◽  
George Vergos ◽  
Emmanuel M. Scordilis
Keyword(s):  
Global Positioning System ◽  
High Frequency ◽  
Main Shock ◽  
Tectonic Activity ◽  
Electron Content ◽  
Ionospheric Turbulence ◽  
Total Electron ◽  
Discrete Fourier Analysis ◽  
Hellenic Arc ◽  
Global Positioning

<p>In this paper we investigate the ionospheric turbulence from TEC observations before and during the tectonic activity of the last quarter of 2019 in the Hellenic Arc, Greece (main shock at l=23.26<sup>o</sup>E, j=35.69<sup>o</sup>N, M<sub>w</sub>=6.1). The Total Electron Content (TEC) data of 6 Global Positioning System (GPS) stations of the EUREF network, which are being provided by IONOLAB (Turkey), were analysed using Discrete Fourier Analysis in order to investigate the TEC variations. The results of this investigation indicate that the High- Frequency limit f<sub>o</sub>, of the ionospheric turbulence content, increases by aproaching the site and the time of the earthquake occurrence, pointing to the earthquake location (epicenter). We conclude that the LAIC mechanism through acoustic or gravity wave could explain this phenomenology.</p>

scholarly journals Lower Ionospheric Turbulence Variations During the Recent Activity of Etna’s Volcano, Sicily, in December 2018

2019 ◽  
Vol 55 (1) ◽  
pp. 19
Author(s):  
Michael E. Contadakis ◽  
Demeter Arabelos ◽  
Emmanuel Scordilis
Keyword(s):  
Gravity Waves ◽  
High Frequency ◽  
Mount Etna ◽  
Eastern Coast ◽  
Earthquake Activity ◽  
Etna Volcano ◽  
Ionospheric Turbulence ◽  
Frequency Limit ◽  
Recent Activity ◽  
Nearby City

In this paper, we present an investigation on the ionospheric turbulence from TEC observations before and during the recent activity of Etna’s Volcano. Mount Etna is located close to the eastern coast of Sicily. The last eruption of Etna volcano took place on 24 December 2018 while two days later (26 December, 02:19 UTC) an earthquake of M=5.0 occurred ~15 km to the ESE of the volcano, causing damage to the nearby city of Catania. The results of our investigation, on the occasion of the Etna’s Volcanic activity, indicate that the high-frequency limit fo  of the ionospheric turbulence band content, is increasing with time to the volcano eruption while, at the same time, fo isdecreasing with distance from the volcano. We conclude that the LAIC mechanism through acoustic or gravity waves could explain this phenomenology, as it has happened in cases of earthquake activity. Our observations indicate that the effect of volcanic eruption on the band content of the ionospheric turbulence is insignificant at distances greater than 1000km (at the most), a fact that we must consider in our research on Ionospheric turbulence in relation to earthquake precursors research.

Lower Ionospheric variations during the intense tectonic activity in the broader area of Greece on October of 2020

2021 ◽  
Author(s):  
Michael E. Contadakis ◽  
Demetrios Arabelos ◽  
Christos Pikridas ◽  
Stelios Bitharis ◽  
Emmanuel M. Scordilis
Keyword(s):  
Statistical Analysis ◽  
Seismic Activity ◽  
Strong Earthquake ◽  
Tectonic Activity ◽  
Activity Period ◽  
Electron Content ◽  
Ionospheric Turbulence ◽  
Eastern Aegean ◽  
The Mediterranean ◽  
Of Greece

<p>In this paper we investigate the Lower ionospheric variations from TEC observations during the intense seismic activity of October 2020 in the area of Greece (35<sup> o</sup> £ j £ 42<sup>o</sup> N, 19<sup> o</sup> £ l £ 29<sup>o</sup> E).  The Total Electron Content (TEC) data are been provided by the  Hermes GNSS Network managed by GNSS_QC, AUTH Greece, the HxGN/SmartNet-Greece of Metrica S.A, and the EUREF Network. These data were analysed using both, statistical analysis of TEC variations in order to detect uneven gross variations and Discrete Fourier Analysis in order to investigate the TEC turbulence. The results of this investigation indicate that the High- Frequency limit f<sub>o</sub> of the ionospheric turbulence content, increases as aproaching the occurrence time of the earthquake, pointing to the earthquake epicenter, in accordane to our previous investigations (Contadakis et al., 2009; Contadakis et al., 2012; Contadakis et al., 2015; Scordilis et al., 2020). We conclude that the LAIC mechanism through acoustic or gravity waves could explain this phenomenology. Thus, observing the frequency content of the ionospheric turbidity we observe a decrease of the higher limit of the turbitity frequency band, as a result of  the differential  frequency attenuation of the propagating wave. In addition, the statistical analysis shows an excess greater than  3σ from the mean TEC values one and seven days before the earthquake. Since no major disturbance of the geomagnetic field occured during these days, we conclude that we probably observed precursory Ionospheric variations in accordance to analogous findings from the variation of VH/VHF electromagnetic wave propagrations over strong earthquake areas (e.g. Biagi et al. 2019)  </p><p> </p><p>References</p><p> </p><p>Biagi and 11 co authors, The INFREP Network: Present Situation andRecent Results. Open Journal of Earthquake Research, vol.8, p. 101-115, 2019.</p><p>Contadakis, M.E., Arabelos, D.N., Asteriadis, G., Spatalas, S.D., Pikridas, C., TEC variations over the Mediterranean during the seismic activity period of the last quarter of 2005 in the area of Greece, Nat. Hazards and Earth Syst. Sci., 8, 1267-1276, 2008.</p><p>Contadakis, M.E., Arabelos, D.N., Asteriadis, G., Spatalas, S.D., Pikridas, C. TEC variations over Southern Europe before and during the M6.3 Abruzzo earthquake of 6<sup>th</sup> April 2009, Annals of Geophysics, vol. 55, iss. 1, p. 83-93, 2012.</p><p>Contadakis, M. E., Arabelos, D.N., Vergos, G., Spatalas, S. D., Scordilis, E.M., 2015,TEC variations over the Mediterranean before and during the strong earthquake (M = 6.5) of 12th October 2013 in Crete, Greece, Physics and Chemistry of the Earth, Volume 85, p. 9-16., 2015.</p><p>Scordilis E.M., Contadakis M.E, Vallianatos  F., Spatalas S., Lower Ionospheric turbulence variations during the intense tectonic activity in Eastern Aegean area, Annals of Geophysics, 63, 5, PA544, 2020</p>

Lower Ionospheric turbulence variations during the intense seismic activity of the last half of 2019 in the broader Balkan region.

2020 ◽  
Author(s):  
Michael E. Contadakis ◽  
Demetrios Arabelos ◽  
George Vergos ◽  
Emmanuel M. Scordilis
Keyword(s):  
Global Positioning System ◽  
Seismic Activity ◽  
Main Shock ◽  
Electron Content ◽  
Marmara Sea ◽  
Ionospheric Turbulence ◽  
Total Electron ◽  
Discrete Fourier Analysis ◽  
Global Positioning ◽  
Balkan Region

<p>In this paper, we investigate the ionospheric turbulence from TEC observations, before and during the intense seismic activity of September 2019 at Albania (main shock at l=19.445<sup>o</sup>E, j=41.372<sup>o</sup> N, M<sub>w</sub>=5.6)  and at Marmara sea (main shock at l=28.19 <sup>o</sup>E, j=40.872<sup>o</sup>N, M<sub>w</sub>=5.7), as well as of November 2019 at Albania (main shock at l=19.470<sup>o</sup>E, j=41.381<sup>o</sup>N, M<sub>w</sub>=6.4), and at Bosnia-Herzegovina (main shock at l=17.961<sup>o</sup>E, j=43.196<sup>o</sup>N, M<sub>w</sub>=5.4).</p><p>The Total Electron Content (TEC) data of 6 Global Positioning System (GPS) stations of the EUREF network, which are being provided by IONOLAB (Turkey), were analysed using Discrete Fourier Analysis in order to investigate the TEC variations. The results of this investigation indicate that the High- Frequency limit f<sub>o</sub>, of the ionospheric turbulence content, increases by aproaching the site and  the time of the earthquake occurrence, pointing to the earthquake location (epicenter). We conclude that the LAIC mechanism, through acoustic or gravity wave, could explain this phenomenology. In addition the proximity of the tectonic active areas to the GPS stations offer us an opportunity to discriminate the origin of the disturbances</p>

scholarly journals Ionospheric turbulence from TEC variations and VLF/LF transmitter signal observations before and during the destructive seismic activity of August and October 2016 in Central Italy

2020 ◽  
Vol 63 (5) ◽  
Author(s):  
Michael Contadakis ◽  
Demetrios Arabelos ◽  
George Vergos ◽  
Christos Skeberis ◽  
Tomas Xenos ◽  
...  
Keyword(s):  
Seismic Activity ◽  
Visual Analysis ◽  
Central Italy ◽  
Electron Content ◽  
Ionospheric Turbulence ◽  
Total Electron ◽  
Discrete Fourier Analysis ◽  
Hilbert Huang Transform ◽  
Global Positioning ◽  
The Moment

In this paper we investigate the ionospheric turbulence from observations of TEC variations as well as from VLF/LF transmitter signal observations before and during the disastrous seismic activity of August and October 2016 in Central Italy. The Total Electron Content (TEC) data of 8 Global Positioning System (GPS) stations of the EUREF network, which are being provided by IONOLAB (Turkey), were analysed using Discrete Fourier Analysis in order to investigate the TEC variations. The data acquired for VLF/LF signal observations are from the receiver of Thessaloniki (40.59N, 22,78E), Greece, which monitor the VLF/LF transmitters of the International Network for Frontier Research on Earthquake Precursors (INFREP). A method of normalization according to the distance between the receiver and the transmitter is applied on the above data and then they are processed by the Hilbert Huang Transform (HHT) to produce the corresponding spectra for visual analysis. The results of both methods indicate that the High- Frequency limit fo, of the ionospheric turbulence content, increases as the site and the moment of the earthquake occurrence is approaching, pointing to the earthquake locus.

Evaluation of Special Hearing Aids for Deaf Children

1971 ◽  
Vol 36 (4) ◽  
pp. 527-537 ◽  
Author(s):  
Norman P. Erber
Keyword(s):  
Hearing Aids ◽  
High Frequency ◽  
Hearing Aid ◽  
Low Frequency ◽  
Acoustic Stimulation ◽  
Deaf Children ◽  
Frequency Range ◽  
Frequency Limit ◽  
Unpublished Studies ◽  
Published Research

Two types of special hearing aid have been developed recently to improve the reception of speech by profoundly deaf children. In a different way, each special system provides greater low-frequency acoustic stimulation to deaf ears than does a conventional hearing aid. One of the devices extends the low-frequency limit of amplification; the other shifts high-frequency energy to a lower frequency range. In general, previous evaluations of these special hearing aids have obtained inconsistent or inconclusive results. This paper reviews most of the published research on the use of special hearing aids by deaf children, summarizes several unpublished studies, and suggests a set of guidelines for future evaluations of special and conventional amplification systems.

Microearthquakes in the Tihamat-Asir region of Saudi Arabia

1980 ◽  
Vol 70 (6) ◽  
pp. 2291-2293
Author(s):  
H. M. Merghelani ◽  
S. K. Gallanthine
Keyword(s):  
Saudi Arabia ◽  
Continental Crust ◽  
Red Sea ◽  
Fault Plane ◽  
Seismic Refraction ◽  
Earthquake Hazard ◽  
Tectonic Activity ◽  
Fault Plane Solutions ◽  
High Level ◽  
Asir Region

abstract During the course of a seismic refraction investigation in Saudi Arabia, an unexpected high level of microearthquake activity was detected near the border of the Red Sea and near the transition from oceanic to continental crust. The data is not adequate to determine fault plane solutions nor to relate the earthquakes to specific structures, but the existence of microearthquakes at this location suggest that there is a significant level of tectonic activity at a point 200 km from an axial trough of the Red Sea. These data, combined with other recent geological observations, may be an important clue to the understanding of continental rifting. The data suggest the need for a more thorough investigation of the earthquake hazard along the shores of the Red Sea.

Measurement of Strain Induced by Impact with Fiber Bragg Grating

2008 ◽  
Vol 381-382 ◽  
pp. 435-438
Author(s):  
Ping Yu Zhu ◽  
D. Liu ◽  
Y. Lin
Keyword(s):  
Composite Material ◽  
Fiber Bragg Grating ◽  
Time Domain ◽  
High Frequency ◽  
Impact Test ◽  
Bragg Grating ◽  
Experiment Data ◽  
Frequency Limit ◽  
Fiber Bragg Grating Sensors ◽  
Frequency Components

After deriving the propagation formula of stress wave through incident bar, the measured signals both in horizontal impact test and drop impact tests are investigated with novel fiber Bragg grating sensors(FBGs). Especially those strain signals from FBGs which mounted on the surface of an incident bar are studied. The signals in impactor and the FBGs embedded in the composite material under similar test condition are compared. The dropping and impacting models have been setup. The experiment data measured in a lab are analyzed both in time-domain and in frequency domain. Those ultra-high frequency components in the above strain signals can not be obtained by current FBG measurement system due to frequency limit of the demodulation system. Further study to improve the frequency of demodulation system will be done in next step.

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