59 results on '"Alexander Rozhnoi"'
Search Results
2. Neural network approach to the prediction of seismic events based on low-frequency signal monitoring of the Kuril-Kamchatka and Japanese regions
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Irina Popova, Alexander Rozhnoi, Maria Solovieva, Boris Levin, Masashi Hayakawa, Yasuhide Hobara, Pier Francesco Biagi, and Konrad Schwingenschuh
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VLF/LF signal propagation ,Neural network ,Earthquakes ,Meteorology. Climatology ,QC851-999 ,Geophysics. Cosmic physics ,QC801-809 - Abstract
Very-low-frequency/ low-frequency (VLF/LF) sub-ionospheric radiowave monitoring has been widely used in recent years to analyze earthquake preparatory processes. The connection between earthquakes with M ≥5.5 and nighttime disturbances of signal amplitude and phase has been established. Thus, it is possible to use nighttime anomalies of VLF/LF signals as earthquake precursors. Here, we propose a method for estimation of the VLF/LF signal sensitivity to seismic processes using a neural network approach. We apply the error back-propagation technique based on a three-level perceptron to predict a seismic event. The back-propagation technique involves two main stages to solve the problem; namely, network training, and recognition (the prediction itself). To train a neural network, we first create a so-called ‘training set’. The ‘teacher’ specifies the correspondence between the chosen input and the output data. In the present case, a representative database includes both the LF data received over three years of monitoring at the station in Petropavlovsk-Kamchatsky (2005-2007), and the seismicity parameters of the Kuril-Kamchatka and Japanese regions. At the first stage, the neural network established the relationship between the characteristic features of the LF signal (the mean and dispersion of a phase and an amplitude at nighttime for a few days before a seismic event) and the corresponding level of correlation with a seismic event, or the absence of a seismic event. For the second stage, the trained neural network was applied to predict seismic events from the LF data using twelve time intervals in 2004, 2005, 2006 and 2007. The results of the prediction are discussed.
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- 2013
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3. Low frequency signal spectrum analysis for strong earthquakes
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Masashi Hayakawa, Konrad Schwingenschuh, Pier Francesco Biagi, Maria Solovieva, and Alexander Rozhnoi
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VLF/LF signal propagation. eartquake precursors ,Meteorology. Climatology ,QC851-999 ,Geophysics. Cosmic physics ,QC801-809 - Abstract
We examined changes in the spectral composition of the low frequency (LF) subionospheric signals from the NRK transmitter (37.5 kHz) in Iceland that were received in Bari (Italy) relative to the earthquake that occurred in L’Aquila on April 6, 2009. In our previous studies, we have reported the occurrence of preseismic night-time anomalies using observations from three receivers located in Bari, Graz (Austria) and Moscow (Russia). The strongest anomalies in the signals were observed in the NRK-Bari propagation path during the period 5-6 days before the L’Aquila earthquake, as well as during the series of aftershocks. During this period, similar very low frequency (VLF)/LF amplitude anomalies were also observed along several other propagation paths that crossed the L’Aquila seismogenic zone. Spectral analysis of the LF signals filtered in the frequency range 0.28 mHz to 15 mHz shows differences in the spectra for seismo-disturbed days when compared to those for either quiet or geomagnetically disturbed days. These spectral anomalies, which are only observed in the propagation path between NRK and Bari, contain signals with periods of about 10 min to 20 min. These periodic signals are absent both in the spectra of the undisturbed signals for the control paths, and in the spectra of the signals received during geomagnetic storms. The same changes in the spectral composition were observed in the analysis of LF (40 kHz) signals from the JJY transmitter in Japan that were received in Petropavlovsk-Kamchatsky (Russia) during the occurrence of three strong earthquakes with M ≥7.0. The results of this study support the theoretical prediction that the possible mechanism for energy penetration from the origin of an earthquake through the atmosphere and into the ionosphere is based on the excitation and upward propagation of internal gravity waves.
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- 2012
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4. Ionospheric perturbations associated with two huge earthquakes in Japan, using principal component analysis for multiple subionospheric VLF/LF propagation paths
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Maria Solovieva, Alexander Rozhnoi, Masashi Hayakawa, Yasushi Kasahara, Yasuhide Hobara, Yuichi Ida, Yuya Ono, Oleg A. Molchanov, and Kenji Ohta
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Ionospheric perturbations, Earthquakes, Subionospheric VLF/LF propagation, Principal compornent analysis, Earthquake prediction ,Meteorology. Climatology ,QC851-999 ,Geophysics. Cosmic physics ,QC801-809 - Abstract
The presence of ionospheric perturbations in possible association with two huge earthquakes (Noto-hanto peninsula and Niigata-chuetu-oki earthquakes) in 2007 was studied on the basis of a conventional statistical study for a particular propagation path from the JJI transmitter in Miyazaki, Kyushu, to Moshiri in Hokkaido. This is based on automatic routine-based signal processing, in which the trend as the average nighttime amplitude is significantly decreased, with almost simultaneous significant enhancement in the night-time fluctuation as the night-time integration of negative fluctuation from the average. It is, however, shown that this routine-based signal analysis sometime suffers from artificial (or man-made) effects. Thus, in this study, we propose an additional use of principal component analysis (PCA) for simultaneous observation of a few VLF/LF propagation paths. With the application of this PCA method to multi-path data, the artificial effects can be reasonably removed, and also only the geophysical effects associated with earthquakes are detected, by focusing mainly on the third principal component. The satisfactory separation of the principal components is made possible by pre-analysis of the VLF data (extraction from the raw data of the average over a whole year). This PCA method enables us to identify the seismogenic effects in association with earthquakes with smaller magnitudes, down to M 5.5 or M 5.0.
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- 2012
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5. Ionospheric turbulence from ground-based and satellite VLF/LF transmitter signal observations for the Simushir earthquake (November 15, 2006)
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Pier Francesco Biagi, Masashi Hayakawa, Michel Parrot, Maria Solovieva, Alexander Rozhnoi, and Konrad Schwingenschuh
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Wave propagation, Seismic risk, VLF/LF signal propagation, Eartquake precursors ,Meteorology. Climatology ,QC851-999 ,Geophysics. Cosmic physics ,QC801-809 - Abstract
Signals from very low frequency (VLF)/ low frequency (LF) transmitters recorded on the ground station at Petropavlovsk-Kamchatsky and on board the French DEMETER satellite were analyzed for the Simushir earthquake (M 8.3; November 15, 2006). The period of analysis was from October 1, 2006, to January 31, 2007. The ground and satellite data were processed by a method based on the difference between the real signal at night-time and the model signal. The model for the ground observations was the monthly averaged signal amplitudes and phases, as calculated for the quiet days of every month. For the satellite data, a two-dimensional model of the signal distribution over the selected area was constructed. Preseismic effects were found several days before the earthquake, in both the ground and satellite observations.
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- 2012
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6. The Ionospheric Precursor to the 2011 March 11 Earthquake Based upon Observations Obtained from the Japan-Pacific Subionospheric VLF/LF Network
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Masashi Hayakawa, Yasuhide Hobara, Alexander Rozhnoi, Maria Solovieva, Kenji Ohta, Jun Izutsu, Tohru Nakamura, and Yasushi Kasahara
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Ionospheric precursor ,VLF/LF subionospheric propagation ,2011 March 11 Japan earthquake ,Geology ,QE1-996.5 ,Geophysics. Cosmic physics ,QC801-809 - Abstract
By using network observation of subionospheric VLF (very low frequency)/LF (low frequency) signals in Japan and in Russia, we have found a significant ionospheric perturbation prior to the recent 2011 March 11 Japan earthquake (EQ) which occurred at sea proximate to the Tohoku area on the main island (Honshu) of Japan was an exceptionally huge plate-type EQ. A remarkable anomaly (with a decrease in the nighttime amplitude and also with enhancement in dispersion) was detected on March 5 and 6 along the propagation path from the NLK (Seattle, USA) transmitter to Chofu (together with Kochi and Kasugai). We also have observed the corresponding VLF anomaly during a prolonged period of March 1 - 6, with minima in the nighttime amplitude on March 3 and 4 along the path from JJI (Miyazaki, Kyushu) to Kamchatka, Russia. This ionospheric perturbation has been discussed extensively with respect to its reliability. (1) How abnormal is this VLF/LF propagation anomaly? (2) What was the temporal evolution of terminator times? (3) Were there any solar-terrestrial effects (especially the effect from geomagnetic storms) on the VLF/LF propagation anomaly? (4) The effect of any other EQs and foreshock activities on the VLF/LF anomaly? (5) Were there any correlations with other related phenomena? Finally, (6) are there any other examples of a VLF/LF propagation anomaly for oceanic EQs? We then compared the temporal properties of ionospheric perturbations for this EQ with those of a huge number of inland EQs and compared the corresponding spatial scale with the former result of the same oceanic 2004 Sumatra EQ with nearly the same magnitude. Finally, the generation mechanism of those seismo-ionospheric perturbations is briefly discussed.
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- 2013
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7. The lower ionosphere disturbances observed during the chain of the meteotsunamis in the Mediterranean Sea in June 2014
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Maria Solovieva, S. L. Shalimov, G. Shevchenko, P. F. Biagi, Alexander Rozhnoi, and Viktor Fedun
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Mediterranean climate ,021110 strategic, defence & security studies ,Atmospheric Science ,Jet (fluid) ,010504 meteorology & atmospheric sciences ,Atmospheric pressure ,0211 other engineering and technologies ,02 engineering and technology ,Low frequency ,Atmospheric sciences ,01 natural sciences ,Physics::Geophysics ,Atmosphere ,Mediterranean sea ,Earth and Planetary Sciences (miscellaneous) ,Ionosphere ,Geology ,0105 earth and related environmental sciences ,Water Science and Technology ,Meteotsunami - Abstract
In June 2014, a number of meteotsunamis were detected in the Mediterranean and Black Sea area. These meteotsunamis were initiated by a unique high-altitude dynamical system which was initially originated above Spain and traveled across the Mediterranean Sea towards Black Sea and Turkey. Meteotsunamis unlike tsunamis driven by strong earthquakes are local events, and their formation has different mechanism. Atmospheric internal gravity waves (IGWs) are one of the main known sources of meteotsunamis (e.g. Vilibic et al. in Pure Appl Geophys 165:2169–2195, 2008). The synoptic system produced short-lived and small-scale atmospheric pressure perturbations which drifted with the jet stream-like bubbles and generated tsunami-like waves in the open waters. The bubbles with typical dimensions 15–60 km continuously form and collapse in the atmosphere at altitudes of 3–6 km. Such a “boiled” atmosphere generated IGWs propagating both downward, where they produced meteotsunamis (presumably under Proudman resonance condition) and upward into the ionosphere, with following dissipation and excitation of plasma density perturbations. One of the few experimental techniques, which can monitor perturbations of the ionization within the lower ionosphere, uses long-wave probing by very low and low frequency (VLF/LF) radio signals. To study the ionospheric disturbances observed during the chain of meteotsunamis affecting the Mediterranean Sea, we used VLF/LF data collected in South Europe by “The International Network for Frontier Research on Earthquake Precursors”. By applying the spectral analysis method to the anomalous VLF/LF signals, it was found that revealed periods of the signal variations were from 10 to 40–70 min in different stations, which are in the range of the atmospheric pressure oscillations and the meteotsunami events. These periods also correspond to the periods of IGWs.
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- 2020
8. Model of the propagation of very low-frequency beams in the Earth–ionosphere waveguide: principles of the tensor impedance method in multi-layered gyrotropic waveguides
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Alexander Rozhnoi, Viktor Fedun, Andrey Gulin, V. V. Grimalsky, Alex Liashchuk, Oleksiy Agapitov, Asen Grytsai, Yuriy Rapoport, John W. Bonnell, Maria Solovieva, and Gennadi Milinevsky
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Atmospheric Science ,010504 meteorology & atmospheric sciences ,Physics::Optics ,010502 geochemistry & geophysics ,01 natural sciences ,Electromagnetic radiation ,Physics::Geophysics ,law.invention ,Optics ,law ,Earth and Planetary Sciences (miscellaneous) ,Very low frequency ,lcsh:Science ,Nonlinear Sciences::Pattern Formation and Solitons ,0105 earth and related environmental sciences ,Physics ,business.industry ,lcsh:QC801-809 ,Metamaterial ,Geology ,Astronomy and Astrophysics ,Polarization (waves) ,lcsh:QC1-999 ,lcsh:Geophysics. Cosmic physics ,Radio propagation ,Space and Planetary Science ,Physics::Space Physics ,lcsh:Q ,Earth–ionosphere waveguide ,business ,Waveguide ,lcsh:Physics ,Radio wave - Abstract
The modeling of very low-frequency (VLF) electromagnetic (EM) beam propagation in the Earth–ionosphere waveguide (WGEI) is considered. A new tensor impedance method for modeling the propagation of electromagnetic beams in a multi-layered and inhomogeneous waveguide is presented. The waveguide is assumed to possess the gyrotropy and inhomogeneity with a thick cover layer placed above the waveguide. The influence of geomagnetic field inclination and carrier beam frequency on the characteristics of the polarization transformation in the Earth–ionosphere waveguide is determined. The new method for modeling the propagation of electromagnetic beams allows us to study the (i) propagation of the very low-frequency modes in the Earth–ionosphere waveguide and, in perspective, their excitation by the typical Earth–ionosphere waveguide sources, such as radio wave transmitters and lightning discharges, and (ii) leakage of Earth–ionosphere waveguide waves into the upper ionosphere and magnetosphere. The proposed approach can be applied to the variety of problems related to the analysis of the propagation of electromagnetic waves in layered gyrotropic and anisotropic active media in a wide frequency range, e.g., from the Earth–ionosphere waveguide to the optical waveband, for artificial signal propagation such as metamaterial microwave or optical waveguides.
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- 2020
9. On electromagnetic precursors to the Hokkaido earthquake in September, 2018 and consideration of lithosphere-atmosphere-ionosphere coupling
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Alexander Rozhnoi, Masashi Hayakawa, Maria Solovieva, and Shih-Sian Yang
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Atmosphere ,Coupling ,Lithosphere ,Geophysics ,Ionosphere ,Geology - Published
- 2019
10. Impact of earthquakes and tsunamis on the ionosphere
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E. V. Ol’shanskaya, M. S. Solov’eva, Alexander Rozhnoi, and S. L. Shalimov
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010504 meteorology & atmospheric sciences ,Acoustic wave ,Geophysics ,010502 geochemistry & geophysics ,01 natural sciences ,Physics::Geophysics ,Internal gravity wave ,symbols.namesake ,Global network ,Physics::Space Physics ,symbols ,General Earth and Planetary Sciences ,Satellite ,Rayleigh wave ,Ionosphere ,Current (fluid) ,Geology ,0105 earth and related environmental sciences ,General Environmental Science - Abstract
Diagnostics of the outer envelopes of the Earth through global satellite navigational systems and through the equally global network of ground receivers and very-low-frequency transmitters make it possible to explore fairly complex processes of lithosphere–ionosphere interactions. The effects of earthquakes and tsunamis on the ionosphere are an example of these processes. A brief review of the current advances in studying these processes is presented.
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- 2019
11. Characterization of sub-ionospheric VLF/LF waveguides for seismic event studies during solar minimum
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Hans Eichelberger, Konrad Schwingenschuh, Mohammed Y. Boudjada, Bruno P. Besser, Daniel Wolbang, Alexander Rozhnoi, Maria Solovieva, Pier Francesco Biagi, Manfred Stachel, Özer Aydogar, Cosima Muck, Claudia Grill, and Irmgard Jernej
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In this study we present measurements and simulations of mid-latitude sub-ionospheric propagation paths between several VLF/LF transmitters and the Graz seismo-electromagnetic receiver facility (Schwingenschuh etal, 2011) during the current solar minimum condition. The upper D/E-region boundary of the waveguide is stable during the low solar activity in the years 2018 and 2019, i.e. measured VLF/LF amplitude and phase variations are mainly due to natural excitations from the lithosphere, atmosphere, and man-made disturbances. In particular, this period gives a baseline to characterize VLF amplitude and phase modulations in the waveguide cavity related to seismic activity over Europe. In addition, this opportunity let us probe the signal threshold and feed-back into waveguide simulation models. We conclude, proven long-term VLF/LF measurements, the continuous monitoring of the cavity, could be valuable in the assessment of seismic hazard scenarios.Ref:Schwingenschuh, K., Prattes, G., Besser, B. P., Mocnik, K., Stachel, M., Aydogar, Ö., Jernej, I., Boudjada, M. Y., Stangl, G., Rozhnoi, A., Solovieva, M., Biagi, P. F., Hayakawa, M., and Eichelberger, H. U.: The Graz seismo-electromagnetic VLF facility, Nat. Hazards Earth Syst. Sci., 11, 1121–1127, https://doi.org/10.5194/nhess-11-1121-2011, 2011.
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- 2020
12. Model of propagation of VLF beams in the waveguide earth-ionosphere. Principles of tensor impedance method in multilayered gyrotropic waveguides
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Maria Solovieva, Asen Grytsai, Gennadi Milinevsky, Alexander Rozhnoi, Victor Fedun, Alex Liashchuk, Andrey Gulin, John W. Bonnell, Yuriy Rapoport, V. V. Grimalsky, and Oleksiy Agapitov
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Physics ,Metamaterial ,Magnetosphere ,Space weather ,Electromagnetic radiation ,law.invention ,Computational physics ,Physics::Geophysics ,law ,Physics::Space Physics ,Ionosphere ,Waveguide ,Microwave ,Radio wave - Abstract
Modeling propagation of VLF electromagnetic beams in the waveguide earth-ionosphere (WGEI) is of a great importance because variation in the characteristics of these waves is an effective instrument for diagnostics the influences on the ionosphere from above (Sun-Solar Wind-Magnetosphere-Ionosphere), from below (the most powerful meteorological, seismogenic and other sources in the lower atmosphere and lithosphere/Earth, such as hurricanes, earthquakes, tsunamis etc.), from inside the ionosphere (strong thunderstorms and lightning discharges) and even from the far space (such as gamma-flashes, cosmic rays etc.). Thus, VLF became one of the most universal instrument for monitoringthe Space Weather in the direct sense of this term, i.e. the state of the Sun-Earth space and the ionosphere as it is particularly determined by all possible relatively powerful sources, wherever they are placed. This paper is devoted mostly to modelling VLF electromagnetic beam propagation in the WGEI. We present a new tensor impedance method for modelling propagation of electromagnetic beams (TIMEB) in a multi-layered/inhomogeneous waveguide. Suppose that such a waveguide, i.e. WGEI, possesses the gyrotropy and inhomogeneity with a thick cover layer placed above the waveguide. Note a very useful and attractive feature of the proposed TIMEB method: in spite of a large thickness of the waveguide cover layer, the proposed effective impedance approach reflects an impact of such a cover on the electromagnetic (EM) waves, which propagate in the waveguide. This impedance approach can be applied for EM waves/beams in layered gyrotropic/anisotropic active media in very wide frequency range, from VLF to optics. Moreover, this approach can be applied to calculations of EM waves/beams propagation in the media of an artificial origin such as metamaterial microwave or optical waveguides. The results of the modelling the propagation of VLF beams in the WGEI are included. The qualitative comparison between the theory and experimental observation of increasing losses of VLF waves in the WGEI is discussed. The new proposed method and its further development allows the comparison with the results of the future rocket experiment. This method allows to model (i) excitation of the VLF modes in the WGEI and their excitation by the typical VLF sources, such as radio wave transmitters and lightning discharges and (ii) leakage of VLF waves/beams into the upper ionosphere/magnetosphere.
- Published
- 2020
13. The Effect of the 21 August 2017 Total Solar Eclipse on the Phase of VLF/LF Signals
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Peter T. Gallagher, Viktor Fedun, Alexander Rozhnoi, Dimitar Ouzounov, Sergiy Shelyag, Gary Verth, S. L. Shalimov, Maria Solovieva, and Joe McCauley
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Physics ,010504 meteorology & atmospheric sciences ,VLF ,Solar eclipse ,lcsh:Astronomy ,lcsh:QE1-996.5 ,Phase (waves) ,solar eclipse ,Environmental Science (miscellaneous) ,Low frequency ,010502 geochemistry & geophysics ,Geodesy ,01 natural sciences ,lcsh:QB1-991 ,lcsh:Geology ,Amplitude ,Middle latitudes ,Physics::Space Physics ,Reflection (physics) ,General Earth and Planetary Sciences ,Astrophysics::Earth and Planetary Astrophysics ,Ionosphere ,0105 earth and related environmental sciences ,Eclipse - Abstract
An experimental study of the phase and amplitude observations of sub‐ionospheric very low and low frequency (VLF/LF) signals is performed to analyze the response of the lower ionosphere during the 21 August 2017 total solar eclipse in the United States of America. Three different sub‐ionospheric wave paths are investigated. The length of the paths varies from 2,200 to 6,400 km, and the signal frequencies are 21.4, 25.2, and 40.75 kHz. The two paths cross the region of the total eclipse, and the third path is in the region of 40–60% of obscuration. None of the signals reveal any noticeable amplitude changes during the eclipse, while negative phase anomalies (from −33° to −95°) are detected for all three paths. It is shown that the effective reflection height of the ionosphere in low and middle latitudes is increased by about 3–5 km during the eclipse. Estimation of the electron density change in the lower ionosphere caused by the eclipse, using linear recombination law, shows that the average decrease is by 2.1 to 4.5 times.
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- 2020
14. The response of VLF signals to the passage of an atmospheric/ionospheric seismic wave after an earthquake in Chile
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Yusupov, Kamil, primary, Alexander, Rozhnoi, additional, Maria, Solovieva, additional, Sergey, Shalimov, additional, Viktor, Fedun, additional, John, Mathews, additional, Ruslan, Sherstyukov, additional, Anvar, Safiullin, additional, and Takashi, Maruyama, additional
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- 2020
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15. Strong influence of solar X-ray flares on low-frequency electromagnetic signals in middle latitudes
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Maria Solovieva, Hans Eichelberger, Peter T. Gallagher, Viktor Fedun, Joseph McCauley, Alexander Rozhnoi, Mohammed Y. Boudjada, and Sergiy Shelyag
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Atmospheric Science ,010504 meteorology & atmospheric sciences ,Astrophysics ,Low frequency ,010502 geochemistry & geophysics ,01 natural sciences ,Spectral line ,law.invention ,law ,Earth and Planetary Sciences (miscellaneous) ,lcsh:Science ,0105 earth and related environmental sciences ,Physics ,Solar flare ,lcsh:QC801-809 ,Geology ,Astronomy and Astrophysics ,lcsh:QC1-999 ,lcsh:Geophysics. Cosmic physics ,Amplitude ,Space and Planetary Science ,Middle latitudes ,Reflection (physics) ,lcsh:Q ,Ionosphere ,lcsh:Physics ,Flare - Abstract
In this paper we analysed sudden phase anomalies (SPAs) of VLF–LF signals recorded at Graz (Austria), Birr (Ireland) and Moscow (Russia) stations during two strong solar flares in September 2017. The first X-class 9.3 flare occurred on 6 September at 12:02 UT, and the second X-class 8.2 flare was observed on 10 September 2017 at 16:06 UT. Data from seven transmitters in a frequency range between 20 and 45 kHz are used for the analysis. The SPAs were observed in all middle-latitude paths (differently orientated) with path lengths from 350 to 7000 km. Solar X-ray burst data were taken from GOES satellite observations in the wavelength band of 0.05–0.4 nm. It was found that (i) the amplitude of SPAs in different paths varies from 10 to 282∘, and (ii) the correlation between the amplitudes of SPAs, the lengths of paths and the signal frequency is weak. The change in effective height of reflection due to lowering of the reflecting layer during the flares was found to be about 12 km for the first event and about 9 km for the second event. Spectral analysis of the X-ray and LF data, filtered in the range between 5 s and 16 min, showed that the LF signal spectra are very similar to X-ray spectra. Maxima of both X-ray and LF spectra are in 2–16 min interval.
- Published
- 2019
16. Author comment
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Alexander Rozhnoi
- Published
- 2019
17. Effect of the total solar eclipse of March 20, 2015, on VLF/LF propagation
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Alexander Rozhnoi, Maria Solovieva, Konrad Schwingenschuh, and Viktor Fedun
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Physics ,010504 meteorology & atmospheric sciences ,Meteorology ,Solar eclipse ,SIGNAL (programming language) ,Phase (waves) ,Geodesy ,01 natural sciences ,Occultation ,Geophysics ,Amplitude ,Space and Planetary Science ,0103 physical sciences ,Effective height ,Ionosphere ,010303 astronomy & astrophysics ,0105 earth and related environmental sciences ,Eclipse - Abstract
The analyzed amplitude and phase variations in electromagnetic VLF and LF signals at 20–45 kHz, received in Moscow, Graz (Austria), and Sheffield (UK) during the total solar eclipse of March 20, 2015, are considered. The 22 analyzed paths have lengths of 200—6100 km, are differently oriented, and cross 40–100% occultation regions. Fifteen paths crossed the region where the occultation varied from 40 to 90%. Solar eclipse effects were found only on one of these paths in the signal phase (–50°). Four long paths crossed the 90–100% occultation region, and signal amplitude and phase anomalies were detected for all four paths. Negative phase anomalies varied from–75° to–90°, and the amplitude anomalies were both positive and negative and were not larger than 5 dB. It was shown that the effective height of the ionosphere varied from 6.5 to 11 km during the eclipse.
- Published
- 2016
18. Neural network technique for identifying prognostic anomalies from low-frequency electromagnetic signals in the Kuril–Kamchatka region
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Maria Solovieva, V. Chebrov, Boris Levin, I. V. Popova, and Alexander Rozhnoi
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010504 meteorology & atmospheric sciences ,Artificial neural network ,Training (meteorology) ,Mode (statistics) ,Induced seismicity ,Low frequency ,010502 geochemistry & geophysics ,01 natural sciences ,Signal ,Amplitude ,General Earth and Planetary Sciences ,Geology ,Seismology ,0105 earth and related environmental sciences ,General Environmental Science ,Event (probability theory) - Abstract
In this paper, we suggest a technique for forecasting seismic events based on the very low and low frequency (VLF and LF) signals in the 10 to 50 Hz band using the neural network approach, specifically, the error back-propagation method (EBPM). In this method, the solution of the problem has two main stages: training and recognition (forecasting). The training set is constructed from the combined data, including the amplitudes and phases of the VLF/LF signals measured in the monitoring of the Kuril-Kamchatka region and the corresponding parameters of regional seismicity. Training the neural network establishes the internal relationship between the characteristic changes in the VLF/LF signals a few days before a seismic event and the corresponding level of seismicity. The trained neural network is then applied in a prognostic mode for automated detection of the anomalous changes in the signal which are associated with seismic activity exceeding the assumed threshold level. By the example of several time intervals in 2004, 2005, 2006, and 2007, we demonstrate the efficiency of the neural network approach in the short-term forecasting of earthquakes with magnitudes starting from M ≥ 5.5 from the nighttime variations in the amplitudes and phases of the LF signals on one radio path. We also discuss the results of the simultaneous analysis of the VLF/LF data measured on two partially overlapping paths aimed at revealing the correlations between the nighttime variations in the amplitude of the signal and seismic activity.
- Published
- 2016
19. Correlation of very low and low frequency signal variations at mid-latitudes with magnetic activity and outer-zone particles
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Alexander Rozhnoi, Konrad Schwingenschuh, Viktor Fedun, B. Levin, Masashi Hayakawa, and Maria Solovieva
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Physics ,Geomagnetic storm ,Atmospheric Science ,Proton ,lcsh:QC801-809 ,Geology ,Astronomy and Astrophysics ,Storm ,Geophysics ,Electron ,Low frequency ,lcsh:QC1-999 ,Physics::Geophysics ,lcsh:Geophysics. Cosmic physics ,Space and Planetary Science ,Middle latitudes ,Physics::Space Physics ,Earth and Planetary Sciences (miscellaneous) ,lcsh:Q ,Ionosphere ,lcsh:Science ,Far East ,lcsh:Physics ,Physics::Atmospheric and Oceanic Physics - Abstract
The disturbances of very low and low frequency signals in the lower mid-latitude ionosphere caused by magnetic storms, proton bursts and relativistic electron fluxes are investigated on the basis of VLF–LF measurements obtained in the Far East and European networks. We have found that magnetic storm (−150 < Dst < −100 nT) influence is not strong on variations of VLF–LF signals. The anomalies with negative amplitude were registered during the main and recovery phases for several magnetic storms (mainly for three northernmost paths). The correlation between VLF–LF signals and geomagnetic activity is rather weak even for these paths (≈ 12–18%). Also, the correlation between magnetic activity and VLF signal variations recorded onboard the DEMETER satellite is not found. The significant influence of outer-zone particles (energetic particle sensor on board/Geostationary Operational Environmental Satellite (GOES) measurements) on the VLF–LF signal variations is found for almost half of the sub-ionospheric paths.
- Published
- 2018
20. Variations of VLF/LF signals observed on the ground and satellite during a seismic activity in Japan region in May–June 2008
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Konrad Schwingenschuh, O. A. Molchanov, Masashi Hayakawa, Michel Parrot, M. Boudjada, P. F. Biagi, Alexander Rozhnoi, Maria Solovieva, Schmidt United Institute of Physics of the Earth [Moscow] (IPE), Russian Academy of Sciences [Moscow] (RAS), Department of Physics [Bari], Università degli studi di Bari Aldo Moro (UNIBA), University of Electro-Communications [Tokyo] (UEC), Space Research Institute of Austrian Academy of Sciences (IWF), Austrian Academy of Sciences (OeAW), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES)
- Subjects
010504 meteorology & atmospheric sciences ,[SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph] ,0211 other engineering and technologies ,02 engineering and technology ,01 natural sciences ,Signal ,lcsh:TD1-1066 ,Large earthquakes ,Real signal ,Satellite data ,lcsh:Environmental technology. Sanitary engineering ,lcsh:Environmental sciences ,0105 earth and related environmental sciences ,lcsh:GE1-350 ,[SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics ,021110 strategic, defence & security studies ,lcsh:QE1-996.5 ,lcsh:Geography. Anthropology. Recreation ,Signal on ,lcsh:Geology ,Signal enhancement ,On board ,lcsh:G ,General Earth and Planetary Sciences ,Satellite ,Seismology ,Geology - Abstract
Signals of two Japanese transmitters (22.2 kHz and 40 kHz) recorded on the ground VLF/LF station in Petropavlovsk-Kamchatsky and on board the DEMETER French satellite have been analyzed during a seismic activity in Japan in May–June 2008. The period of analysis was from 18 April to 27 June. During this time two rather large earthquakes occurred in the north part of Honshu Island – 7 May (M=6.8) and 13 June (M=6.9). The ground and satellite data were processed by a method based on the difference between the real signal in nighttime and the model one. For ground observations a clear decrease in both signals has been found several days before the first earthquake. For the second earthquake anomalies were detected only in JJI signal. The epicenters of earthquakes were in reliable reception zone of 40 kHz signal on board the DEMETER. Signal enhancement above the seismic active region and significant signal intensity depletion in the magnetically conjugate area has been found for satellite observation before the first earthquake. Anomalies in satellite data coincide in time with those in the ground-based observation.
- Published
- 2018
21. Very-Low- to Low-Frequency Sounding of Ionospheric Perturbations and Possible Association with Earthquakes
- Author
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Maria Solovieva, Tomokazu Asano, Alexander Rozhnoi, and Masashi Hayakawa
- Subjects
Depth sounding ,010504 meteorology & atmospheric sciences ,Ionospheric perturbations ,Association (object-oriented programming) ,Geophysics ,Low frequency ,010502 geochemistry & geophysics ,01 natural sciences ,Geology ,0105 earth and related environmental sciences - Published
- 2018
22. VLF/LF signal studies of the ionospheric response to strong seismic activity in the Far Eastern region combining the DEMETER and ground-based observations
- Author
-
Alexander Rozhnoi, Michel Parrot, P. F. Biagi, Viktor Fedun, Konrad Schwingenschuh, Maria Solovieva, Masashi Hayakawa, Schmidt United Institute of Physics of the Earth [Moscow] (IPE), Russian Academy of Sciences [Moscow] (RAS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), University of Electro-Communications [Tokyo] (UEC), Department of Physics [Bari], Università degli studi di Bari Aldo Moro (UNIBA), Space Research Institute of Austrian Academy of Sciences (IWF), Austrian Academy of Sciences (OeAW), University of Sheffield [Sheffield], and Royal Society International Exchanges Scheme and RFBR under Grant 13-05-92602 KOa
- Subjects
Joint analysis ,Signal ,Satellite observations ,Electromagnetic signals ,Geophysics ,Earthquake precursors ,The ionosphere ,[SDU]Sciences of the Universe [physics] ,Geochemistry and Petrology ,Real signal ,Satellite data ,Satellite ,Ionosphere ,Geology ,Remote sensing - Abstract
International audience; The paper presents the results of a joint analysis of ground-based and satellite observations of very low-frequency and low-frequency (VLF/LF) signals during periods of strong seismic activity in the region of Kuril Islands and Japan in 2004–2010. Ground and satellite data was processed using a method based on the difference between the real signal in nighttime and that of a model. The results of the analysis show a good correlation between ground-based and satellite data for several cases of strong (M ⩾ 6.8) earthquakes.
- Published
- 2015
23. Tsunami-driven ionospheric perturbations associated with the 2011 Tohoku earthquake as detected by subionospheric VLF signals
- Author
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Maria Solovieva, Yasuhide Hobara, H. Yamaguchi, Alexander Rozhnoi, Victor Fedun, Masashi Hayakawa, and Boris Levin
- Subjects
lcsh:GE1-350 ,business.industry ,Ionospheric perturbations ,Transmitter ,lcsh:Risk in industry. Risk management ,Low frequency ,lcsh:TD1-1066 ,Physics::Geophysics ,lcsh:HD61 ,Internal gravity wave ,Amplitude ,Physics::Space Physics ,Global Positioning System ,General Earth and Planetary Sciences ,Very low frequency ,Ionosphere ,lcsh:Environmental technology. Sanitary engineering ,business ,Geology ,Seismology ,lcsh:Environmental sciences ,General Environmental Science - Abstract
The subionospheric data from a Japanese very low frequency/low frequency (VLF/LF) receiving station at Moshiri, Hokkaido, are used to detect the response of the lower ionosphere to the tsunami triggered by the 2011 Tohoku earthquake. Disturbances in the phase and amplitude of VLF signals propagating from the transmitter in Hawaiian Islands are observed during the tsunami wave passage, and these effects in the ionosphere are compared to the in situ sea-level global positioning system (GPS) measurements near Japan. The frequency of the maximum spectral amplitude both for the VLF and GPS data is found to be in the range of periods of 8–50 min, which is likely to correspond to the period of the internal gravity waves generated by the tsunami.
- Published
- 2014
24. Detection of tsunami-driven phase and amplitude perturbations of subionospheric VLF signals following the 2010 Chile earthquake
- Author
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Simon Walker, G. Shevchenko, S. Shalimov, Alexander Rozhnoi, Maria Solovieva, Masashi Hayakawa, Boris Levin, Viktor Fedun, and Yasuhide Hobara
- Subjects
Internal gravity wave ,Geophysics ,Amplitude ,Space and Planetary Science ,Epicenter ,Phase (waves) ,Ionosphere ,Bottom pressure ,Pacific ocean ,Geology ,Seismology - Abstract
We report on specific fluctuations in phase and amplitude of VLF signals that correlate both spatially and temporally with the passage of the tsunamis recorded by the Deep-ocean Assessments and Reporting of Tsunamis bottom pressure stations. Measurements from the VLF/LF receiver sited in Petropavlovsk-Kamchatsky and sensor buoys placed throughout the Pacific Ocean at great distances (Hawaii and Japan) from the epicenter are consistent with the hypothesis that the ocean tsunami following the Chile earthquake on 27 February 2010 radiated internal gravity waves which propagated through the lower ionosphere.
- Published
- 2014
25. Excitation of planetary electromagnetic waves in the inhomogeneous ionosphere
- Author
-
Alexander Rozhnoi, Eugen N. Tkachenko, Yuriy Rapoport, V.M. Ivchenko, V. V. Grimalsky, Viktor Fedun, and Yu.A. Selivanov
- Subjects
Physics ,Atmospheric Science ,lcsh:QC801-809 ,Geology ,Astronomy and Astrophysics ,Geophysics ,F region ,Electromagnetic radiation ,lcsh:QC1-999 ,Computational physics ,Magnetic field ,lcsh:Geophysics. Cosmic physics ,Nonlinear system ,Earth's magnetic field ,Space and Planetary Science ,Physics::Space Physics ,Earth and Planetary Sciences (miscellaneous) ,lcsh:Q ,Ionosphere ,Magnetohydrodynamics ,lcsh:Science ,Series expansion ,lcsh:Physics - Abstract
In this paper we develop a new method for the analysis of excitation and propagation of planetary electromagnetic waves (PEMW) in the ionosphere of the Earth. The nonlinear system of equations for PEMW, valid for any height, from D to F regions, including intermediate altitudes between D and E and between E and F regions, is derived. In particular, we have found the system of nonlinear one-fluid MHD equations in the β-plane approximation valid for the ionospheric F region (Aburjania et al., 2003a, 2005). The series expansion in a "small" (relative to the local geomagnetic field) non-stationary magnetic field has been applied only at the last step of the derivation of the equations. The small mechanical vertical displacement of the media is taken into account. We have shown that obtained equations can be reduced to the well-known system with Larichev–Reznik vortex solution in the equatorial region (see e.g. Aburjania et al., 2002). The excitation of planetary electromagnetic waves by different initial perturbations has been investigated numerically. Some means for the PEMW detection and data processing are discussed.
- Published
- 2014
26. Ionospheric effects of the Mt. Kirishima volcanic eruption as seen from subionospheric VLF observations
- Author
-
Viktor Fedun, Maria Solovieva, Alexander Rozhnoi, Masashi Hayakawa, and Yasuhide Hobara
- Subjects
Atmospheric Science ,Daytime ,geography ,Vulcanian eruption ,geography.geographical_feature_category ,Explosive eruption ,Atmospheric gravity waves ,Geophysics ,Internal gravity wave ,Volcano ,Space and Planetary Science ,Spectral amplitude ,Ionosphere ,Geology ,Seismology - Abstract
Data from the Pacific network of VLF receivers have been used to study the response of the lower ionosphere to the January 2011 Mt. Kirishima (South Japan) volcanic eruption. A major explosive eruption occurred on January 27, which was preceded by several small eruptions. Perturbations of nighttime subionospheric VLF signals have been detected on the day of the first small eruption on January 18 (UT) with the maximum observed about 1.5 h after the eruption. The nighttime signal remained disturbed during the subsequent pre-eruptive and eruptive activity of Mt. Kirishima. The daytime perturbations were not observed. The frequency of the maximum spectral amplitude was found to be in the range of periods of 6–30 min, which corresponds to the periods of internal gravity waves. These results suggest that the observed VLF ionospheric effects can possibly be produced by the penetration of gravity waves caused by the volcanic activity into the ionosphere.
- Published
- 2014
27. The lower ionospheric perturbation as a precursor to the 11 March 2011 Japan earthquake
- Author
-
Yasuhide Hobara, Masashi Hayakawa, Kenji Ohta, A. Schekotov, Maria Solovieva, E. N. Fedorov, and Alexander Rozhnoi
- Subjects
Geography ,Ionospheric perturbations ,Anomaly (natural sciences) ,Physics::Space Physics ,General Earth and Planetary Sciences ,Very low frequency ,Ultra low frequency ,Seismology ,Physics::Geophysics ,General Environmental Science - Abstract
It is found that clear lower ionospheric perturbations appeared as a precursor to the 11 March 2011 Japan earthquake. This study is based on the observation of two completely different phenomena: (1) subionospheric very low frequency/low frequency propagation anomaly on the NLK (Seattle, USA) – Chofu propagation path, and (2) depression of magnetospheric ultra low frequency emissions observed on the ground (Kakioka, etc.). But, both effects are suggested to be interpreted by a unified phenomenon of seismo-lower ionospheric perturbation because they occurred on the days of 5 and 6 March, 2011.
- Published
- 2013
28. On the Relative Effect of Magnitude and Depth of Earthquakes in the Generation of Seismo-Ionospheric Perturbations at Middle Latitudes as Based on the Analysis of Subionospheric Propagation Data of JJY (40 kHz)-Kamchatka Path
- Author
-
Alexander Rozhnoi, Maria Solovieva, and Masashi Hayakaw
- Subjects
Geography ,Ionospheric perturbations ,Middle latitudes ,Earthquake prediction ,Magnitude (mathematics) ,Context (language use) ,Seismology - Abstract
The relative importance of magnitude and depth of an earthquake (EQ) in the generation of seismo-ionospheric perturbations at middle latitudes is investigated by using the EQs near the propagation path from the Japanese LF transmitter, JJY (at Fukushima) to a receiving station at Petropavsk-Kamchatsky (PTK) in Russia during a three-year period of 2005-2007. It is then found that the depth (down to 100km) is an extremely unimportant factor as compared with the magnitude in inducing seismo-ionospheric perturbations at middle latitudes. This result for sea EQs in the Izu-Bonin and Kurile-Kamchatka arcs is found to be in sharp contrast with our previous result for Japanese EQs mainly of the fault-type. We try to interpret this difference in the context of the lithosphere-atmosphere-ionosphere coupling mechanism.
- Published
- 2013
29. Ionospheric perturbations related to the earthquake in Vrancea area on November 22, 2014, as detected by electromagnetic VLF/LF frequency signals
- Author
-
Alexander Rozhnoi, Viktor Fedun, Konrad Schwingenschuh, Maria Solovieva, and Masashi Hayakawa
- Subjects
Ionospheric perturbations ,Low frequency wave propagation ,lcsh:QC801-809 ,Magnitude (mathematics) ,lcsh:QC851-999 ,Low frequency ,Geodesy ,Signal ,lcsh:Geophysics. Cosmic physics ,Geophysics ,Amplitude ,Seismic risk ,Earthquake precursors ,lcsh:Meteorology. Climatology ,Ionosphere ,Seismology ,Geology - Abstract
Data from the European network of very low/ low frequency (VLF/LF) receivers has been used to study the response of the lower ionosphere to the earthquake of magnitude 5.5 in Vrancea area on November 22, 2014. Negative amplitude anomalies have been observed during 3 days before the earthquake and two days after, on the LF (45.9 kHz) signal passed above the seismic area. No perturbations have been found for the same signal in control paths during this period. Other possible influences both from above and below which can produce perturbations in the ionosphere have been taken into consideration.
- Published
- 2015
30. The Graz seismo-electromagnetic VLF facility
- Author
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Manfred Stachel, Irmgard Jernej, Gustav Prattes, H. U. Eichelberger, G. Stangl, Masashi Hayakawa, Mohammed Y. Boudjada, Bruno P. Besser, Maria Solovieva, Konrad Schwingenschuh, Ö. Aydogar, K. Močnik, Alexander Rozhnoi, and P. F. Biagi
- Subjects
lcsh:GE1-350 ,Engineering ,business.industry ,lcsh:QE1-996.5 ,Electrical engineering ,lcsh:Geography. Anthropology. Recreation ,lcsh:TD1-1066 ,lcsh:Geology ,Software ,lcsh:G ,General Earth and Planetary Sciences ,Very low frequency ,lcsh:Environmental technology. Sanitary engineering ,business ,lcsh:Environmental sciences - Abstract
In this paper we describe the Graz seismo-electromagnetic very low frequency (VLF) facility, as part of the European VLF receiver network, together with the scientific objectives and results from two years operation. After a brief technical summary of the present system – with heritage from a predecessor facility – i.e. hardware, software, operational modes and environmental influences, we discuss results from statistical data and scientific events related to terrestrial VLF propagation over Europe.
- Published
- 2011
31. Atmospheric gravity waves as a possible candidate for seismo-ionospheric perturbations
- Author
-
Maria Solovieva, Masashi Hayakawa, O. A. Molchanov, Y. Kasahara, Valery Korepanov, Yasuhide Hobara, Takashi Nakamura, and Alexander Rozhnoi
- Subjects
Ionospheric perturbations ,Atmospheric gravity waves ,Geophysics ,Atmospheric sciences ,Geology - Published
- 2011
32. A statistical study on the AGW modulations in subionospheric VLF/LF propagation data and consideration of the generation mechanism of seismo-ionospheric perturbations
- Author
-
Alexander Rozhnoi, Masashi Hayakawa, Takashi Nakamura, Y. Kasahara, O. A. Molchanov, Yasuhide Hobara, and Maria Solovieva
- Subjects
Ionospheric perturbations ,Geophysics ,Mechanism (sociology) ,Seismology ,Geology - Published
- 2010
33. Anomalies in VLF radio signals prior the Abruzzo earthquake (M=6.3) on 6 April 2009
- Author
-
P. F. Biagi, A. Ermini, O. A. Molchanov, Maria Solovieva, Alexander Rozhnoi, Mohammed Y. Boudjada, L. Castellana, Masashi Hayakawa, Konrad Schwingenschuh, and Tommaso Maggipinto
- Subjects
Epicenter ,Terminator (solar) ,General Earth and Planetary Sciences ,Signal ,Seismology ,Geology - Abstract
The VLF/LF radio signals method for studying preseimic activity is applied to the Abruzzo earthquake (M=6.3, 6 April 2009). The data collected by three receivers located in Moscow (Russia), Graz (Austria) and Bari (Italy) at about 3000 km, 1000 km and 500 km from the epicenter were used. The signals received from the Sardinia (20.27 kHz) and the Sicily (45.9 kHz) transmitters, both located in Italy, were compared with those received from the Iceland (37.5 kHz), the Great Britain (19.58 kHz) and the Germany (23.4 kHz) transmitters. The propagation paths of the two Italian transmitters cross the epicentral area (seismic paths) unlike the paths of the other three signals (control paths). Using two different analyses, that are the study of the night-time signal and the research of shifts in the evening terminator times, clear anomalies were revealed 2–8 days before the occurrence of the Abruzzo earthquake in the seismic paths, while no anomalies have been found in the control paths.
- Published
- 2009
34. Variations in the parameters of VLF signals on the DEMETER satellite during the periods of seismic activity
- Author
-
Maria Solovieva, O. A. Molchanov, and Alexander Rozhnoi
- Subjects
Wave propagation ,Geophysics ,Residual ,Signal ,Physics::Geophysics ,Amplitude ,Space and Planetary Science ,Satellite data ,Physics::Space Physics ,Satellite ,Time variations ,Ionosphere ,Geology ,Seismology - Abstract
Two methods for diagnosing ionospheric disturbances using VLF signals received on the DEMETER satellite are considered in connection with two cases of high seismic activity: the method for analyzing a signal reception zone in order to find large-scale spatial variations and the residual signal method used to reveal time variations. Based on an analysis of the VLF signal reception zone, performed in connection with the catastrophic earthquake near Sumatra, it has been found out that the signal amplitude decreased during a month before the earthquake. As a result, it has been concluded that the zone of ionospheric disturbances extends for several thousand kilometers. It has been indicated that the residual signal method showed good agreement between the ground and satellite data when high seismic activity near Japan was analyzed.
- Published
- 2009
35. Further study on the role of atmospheric gravity waves on the seismo-ionospheric perturbations as detected by subionospheric VLF/LF propagation
- Author
-
Masashi Hayakawa, Alexander Rozhnoi, F. Muto, Yasuhide Hobara, O. A. Molchanov, Maria Solovieva, and Y. Kasahara
- Subjects
lcsh:GE1-350 ,Ionospheric perturbations ,lcsh:QE1-996.5 ,lcsh:Geography. Anthropology. Recreation ,Magnitude (mathematics) ,Atmospheric gravity waves ,Geophysics ,lcsh:TD1-1066 ,lcsh:Geology ,Amplitude ,lcsh:G ,Tidal force ,General Earth and Planetary Sciences ,lcsh:Environmental technology. Sanitary engineering ,lcsh:Environmental sciences ,Geology - Abstract
As the target earthquake we have taken a huge earthquake (EQ) named Miyagi-oki earthquake on 16 August 2005 (with magnitude of 7.2) and we have analyzed the 4 month period including the date of this EQ. In addition to our previous analysis on the nighttime average amplitude (trend) and nighttime fluctuation, we have proposed the use of fluctuation power spectra in the frequency rage of atmospheric gravity waves (period=10 min to 100 min) as a third parameter of subionospheric VLF/LF propagation characteristics. Then it is found that this third parameter would be of additional importance in confirming the presence of seismo-ionospheric perturbations. Finally, we have discovered an important role of lunar tidal effect in the VLF/LF data, which appears one and two months before this large EQ.
- Published
- 2009
36. Ionospheric perturbations related to the Miyagi-oki earthquake on 16 August 2005, as seen from Japanese VLF/LF subionospheric propagation network
- Author
-
Masashi Hayakawa, Maria Solovieva, T. Horie, Alexander Rozhnoi, O. A. Molchanov, F. Muto, and M. Yoshida
- Subjects
Geophysics ,Amplitude ,Geochemistry and Petrology ,Ionospheric perturbations ,Magnitude (mathematics) ,Very low frequency ,Low frequency ,Seismology ,Geology - Abstract
A case study has been performed on the lower ionospheric perturbations as seen from the Japanese subionospheric VLF (very low frequency, 3–30 kHz) /LF (low frequency, 30–300 kHz) propagation network for a recent powerful earthquake, i.e., the Miyagi-oki earthquake on 16 August 2005 (magnitude 7.2, and depth 36 km). Different propagation paths were examined and the two paths from a transmitter with call sign of JJY ( f = 40 kHz, in Fukushima prefecture) to both receiving stations of Kamachatka, Russia and Moshiri, Hokkaido, exhibit clear signatures of ionospheric perturbations a few days before and a few days after the earthquake. We have detected a clear nighttime amplitude decrease and an enhancement in nighttime fluctuation, both exceeding the corresponding three standard deviations from the mean. We discuss other seismogenic phenomena in order to study the lithosphere–ionosphere coupling.
- Published
- 2009
37. Disturbances in a VLF radio signal prior the M=4.7 offshore Anzio (central Italy) earthquake on 22 August 2005
- Author
-
L. Castellana, Luigi Schiavulli, Alexander Rozhnoi, Tommaso Maggipinto, Masashi Hayakawa, A. Ermini, P. F. Biagi, Maria Solovieva, O. A. Molchanov, Vincenzo Augelli, D. Loiacono, and Vittorio Capozzi
- Subjects
law ,Radio signal ,Epicenter ,Anomaly (natural sciences) ,General Earth and Planetary Sciences ,Magnitude (mathematics) ,Radio receiver ,Submarine pipeline ,Signal ,Seismology ,Geology ,law.invention - Abstract
On 22 August 2005 an earthquake with magnitude M=4.7 occurred in the Anzio (central Italy) offshore area. From 2002, a VLF-LF radio receiver is into operation in Bari (southern Italy). The intensity and the phase of the signals transmitted by GB (f=16 kHz, United Kingdom), FR (f=20.9 kHz, France), GE (f=23.4 kHz, Germany), IC (f=37.5 kHz, Island) and IT (f=54 kHz, Sicily, Italy) has been monitored with a 5 s sampling rate. The previous epicenter is near enough to some of the radio paths and the data collected were studied in order to reveal possible seismic effects. The raw analysis revealed a clear drop in the intensity of the FR radio signal on 19 August. Then the wavelet analysis was applied to the intensity and the phase data of the different radio signals. In the mentioned day an increase in the band 60–120 min was revealed in the spectra of the FR signal. Then the principal component analysis was applied and again the 19 August stood up as an anomalous day for the FR radio signal. The path of this signal, among the paths of the five radio signals collected by the Bari receiver, is the nearest to the mentioned epicentre and the anomaly revealed on 19 August appears as a precursor of the earthquake. This result confirms the possible precursor revealed by other researchers in the air Rn content in a site located 5 miles far from the epicenter.
- Published
- 2008
38. On the statistical correlation between the ionospheric perturbations as detected by subionospheric VLF/LF propagation anomalies and earthquakes
- Author
-
T. Horie, Maria Solovieva, M. Yoshida, Alexander Rozhnoi, Francesco Muto, O. A. Molchanov, Kenji Ohta, Y. Kasahara, and Masashi Hayakawa
- Subjects
lcsh:GE1-350 ,Fresnel zone ,Epoch (astronomy) ,Ionospheric perturbations ,lcsh:QE1-996.5 ,lcsh:Geography. Anthropology. Recreation ,Magnitude (mathematics) ,Geodesy ,Standard deviation ,lcsh:TD1-1066 ,lcsh:Geology ,Amplitude ,lcsh:G ,General Earth and Planetary Sciences ,lcsh:Environmental technology. Sanitary engineering ,Seismology ,Geology ,Statistical correlation ,lcsh:Environmental sciences ,Line (formation) - Abstract
Relatively long-period (4 years) data on different propagation paths by means of Japanese-Pacific VLF/LF network observation, are used to obtain further statistical significance on the correlation of ionospheric perturbations as revealed by VLF/LF propagation anomalies with earthquakes. Earthquakes with magnitude greater than 6.0, taken place only within the fifth Fresnel zone of each great-circle path are selected for the correlation study. It is finally found based on the superimposed epoch analysis that the nighttime trend (average amplitude) exhibits a significant decrease exceeding 2σ (σ: standard deviation) several days before the earthquake and the nighttime fluctuation exceeds the corresponding 2σ again several days before the earthquake when the earthquake depth is smaller than 30 km (shallow earthquakes). However, when we treat all earthquakes including deep earthquakes, the trend shows a significant decrease (just approaching 2σ line), and the nighttime fluctuation shows a less significant broad enhancement before the EQ.
- Published
- 2008
39. Global diagnostics of the ionospheric perturbations related to the seismic activity using the VLF radio signals collected on the DEMETER satellite
- Author
-
L. Castellana, O. Akentieva, O. A. Molchanov, P. F. Biagi, François Lefeuvre, Alexander Rozhnoi, Masashi Hayakawa, Maria Solovieva, Michel Parrot, Jean-Jacques Berthelier, Schmidt United Institute of Physics of the Earth [Moscow] (IPE), Russian Academy of Sciences [Moscow] (RAS), Space Research Institute of the Russian Academy of Sciences (IKI), Centre d'étude des environnements terrestre et planétaires (CETP), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de physique et chimie de l'environnement (LPCE), Université d'Orléans (UO)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Department of Physics [Bari], Università degli studi di Bari Aldo Moro (UNIBA), and University of Electro-Communications [Tokyo] (UEC)
- Subjects
010504 meteorology & atmospheric sciences ,[SDU.STU]Sciences of the Universe [physics]/Earth Sciences ,010502 geochemistry & geophysics ,01 natural sciences ,lcsh:TD1-1066 ,Physics::Geophysics ,Large earthquakes ,lcsh:Environmental technology. Sanitary engineering ,[SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment ,lcsh:Environmental sciences ,0105 earth and related environmental sciences ,[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere ,lcsh:GE1-350 ,Gravitational wave ,Ionospheric perturbations ,Scattering ,lcsh:QE1-996.5 ,lcsh:Geography. Anthropology. Recreation ,World wide ,lcsh:Geology ,On board ,lcsh:G ,Physics::Space Physics ,General Earth and Planetary Sciences ,Ionosphere ,Phenomenology (particle physics) ,Seismology ,Geology - Abstract
The analysis of the VLF signals radiated by ground transmitters and received on board of the French DEMETER satellite, reveals a drop of the signals (scattering spot) connected with the occurrence of large earthquakes. The extension of the "scattering spots" zone is large enough (1000–5000 km) and, probably, it increases with the magnitude of the "relative" earthquake. A possible model to explain the phenomenology, based on the acoustic gravity waves and the ionosphere turbulence, is proposed. The method of diagnostics applied to this study has the advantage to be a global one due to the world wide location of the powerful VLF transmitters and of the satellite reception. However, a specific disadvantage exists because the method requires rather a long time period of analysis due to the large longitudinal displacements among the successive satellite orbits. At the moment, at least, one month seems to be necessary.
- Published
- 2006
40. Sensitivity of LF signal to global ionosphere and atmosphere perturbations in the network of stations
- Author
-
S. Maekawa, Masashi Hayakawa, Maria Solovieva, Alexander Rozhnoi, O. A. Molchanov, and P. F. Biagi
- Subjects
Physics ,Geomagnetic storm ,Geophysics ,Amplitude ,Earth's magnetic field ,Geochemistry and Petrology ,Transmitter ,Phase (waves) ,Ionosphere ,Atmospheric sciences ,Sensitivity (electronics) ,Signal ,Physics::Geophysics - Abstract
Variations of the LF signal from observations in 6 receiving stations during 2000–2004 are analyzed. Five stations are located in Japan (Kochi, Moshiri, Kasugai, Shimizu and Chiba) and one station is in Russia (Petropavlovsk–Kamchatski). All the stations are equipped with the identical OMNIPAL receivers. JJY (40 kHz) transmitter is situated in Fukushima prefecture (Japan). Sensitivity of the phase and amplitude of the LF signal to ionosphere and atmosphere perturbations associated with variations of the magnetic and meteorological conditions and solar activity is studied. Correlation of phase and amplitude variations of the LF signal with D st -index, outer-zone particles (protons and electrons) with high-pitch angle is established for all the stations. It is found that LF anomalies are typical for the main phase of magnetic storm if the sudden commencement happens in the night time. The similarity of phase and amplitude anomalies to the structure of the simultaneously observed Pi3 geomagnetic pulsations is found for all the stations. Correlation between variations of atmosphere pressure and amplitude of the LF signal is established. Correlation between variations of humidity for the stations located on the coast of Japan and amplitude of the LF signal is found.
- Published
- 2006
41. Preseismic anomaly of LF signal on the wave path Japan–Kamchatka during November–December 2004
- Author
-
O. A. Molchanov, Alexander Rozhnoi, P. F. Biagi, V. Voropaev, S. Maekawa, V. Chebrov, Masashi Hayakawa, and Maria Solovieva
- Subjects
Geophysics ,Amplitude ,Geochemistry and Petrology ,Terminator (solar) ,Anomaly (natural sciences) ,Ionosphere ,Signal on ,Geology ,Seismology - Abstract
The variations of phase and amplitude of LF signal propagating from the transmitter JJY (40 kHz, Fukushima prefecture, Japan) are analyzed. The receiver is situated in Petropavlovsk-Kamchatski (Russia). The time interval from July1, 2004 till January 24, 2005 is included in the examination. This interval is characterized by quiet seismic conditions up to the beginning of November, but rather strong seismic activity occurs in November and December not far from Hokkaido (Japan) and in the region of northern Kuril Islands. Seismic activity in a zone of sensitivity of our wave paths is determined by three series of earthquakes with M = 5.6–7.1. Nighttime “bay-like” phase and amplitude anomalies of the LF signal begin some days before the first earthquake and continue till the last earthquake of this series ( M = 6.2, November 11, 2004). Most strong and obvious anomalies appear in the amplitude of the LF signal. After that, during about one fortnight a period of seismic calm is observed. Then there is a following anomaly of the LF signal before two earthquakes ( M = 7.1, 28.11.04 and M = 6.8, 6.12.04). The next LF anomaly is observed before the earthquakes on December, 18 and 21 ( M = 5.8 and M = 5.6). During the whole period of seismic activity a significant shift in terminator times is also evident. The spectrum of LF seismo-induced anomalies shows a clear increase for the periods of 10–25 min.
- Published
- 2006
42. Anomalies of LF signal during seismic activity in November–December 2004
- Author
-
Alexander Rozhnoi, Maria Solovieva, Masashi Hayakawa, O. A. Molchanov, S. Maekawa, and P. F. Biagi
- Subjects
lcsh:GE1-350 ,Series (stratigraphy) ,Terminator (solar) ,lcsh:QE1-996.5 ,lcsh:Geography. Anthropology. Recreation ,Signal ,lcsh:TD1-1066 ,lcsh:Geology ,lcsh:G ,General Earth and Planetary Sciences ,lcsh:Environmental technology. Sanitary engineering ,Geology ,Seismology ,lcsh:Environmental sciences - Abstract
A signal transmitted by Japan Time Standard LF station (40 kHz, Fukushima prefecture) and recorded in Petropavlovsk-Kamchatski (Russia) is analyzed during a time interval from 1 July 2004 till 24 January 2005. This interval is characterized by quiet seismic conditions up to the beginning of November, but rather strong seismic activity occurs in November and December not far from Hokkaido (Japan) and in the region of northern Kuril Islands. There were three series of earthquakes with M=5.6–7.1 in a zone of sensitivity of our wave path during two months. Nighttime "bay-like" phase and amplitude anomalies of the LF signal are observed several days before and during every series of earthquakes. During the whole period of seismic activity a significant shift in terminator times is also evident. The spectrum of LF seismo-induced anomalies shows a clear increase for the period of about 25 min.
- Published
- 2005
43. Lithosphere-atmosphere-ionosphere coupling as governing mechanism for preseismic short-term events in atmosphere and ionosphere
- Author
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A. Schekotov, P. F. Biagi, A. Lutikov, E. N. Fedorov, Alexander Rozhnoi, S. Yunga, Vadim Surkov, D.I. Iudin, O. A. Molchanov, Masashi Hayakawa, E. Gordeev, S. Andreevsky, V. Chebrov, Inst. of the Physics of the Earth, Russian Academy of Sciences [Moscow] (RAS), Institute of Volcanology and Seismology of the RAS, Far Eastern Branch of the Russian Academy of Sciences (FEB RAS), Geophysical Survey, the Russian Academy of Sciences [Moscow, Russia] (RAS), Radiophysical Research Institute (NIRFI), University of Electro-Communications [Tokyo] (UEC), and Università degli studi di Bari Aldo Moro (UNIBA)
- Subjects
010504 meteorology & atmospheric sciences ,Bubble ,[SDU.STU]Sciences of the Universe [physics]/Earth Sciences ,Perturbation (astronomy) ,010502 geochemistry & geophysics ,01 natural sciences ,lcsh:TD1-1066 ,Physics::Geophysics ,Atmosphere ,Lithosphere ,lcsh:Environmental technology. Sanitary engineering ,[SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment ,lcsh:Environmental sciences ,0105 earth and related environmental sciences ,lcsh:GE1-350 ,[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere ,Physics ,Anomaly (natural sciences) ,lcsh:QE1-996.5 ,lcsh:Geography. Anthropology. Recreation ,Geophysics ,Foreshock ,lcsh:Geology ,Coupling (physics) ,lcsh:G ,13. Climate action ,Physics::Space Physics ,General Earth and Planetary Sciences ,Astrophysics::Earth and Planetary Astrophysics ,Ionosphere ,Seismology - Abstract
We present a general concept of mechanisms of preseismic phenomena in the atmosphere and ionosphere. After short review of observational results we conclude: 1. Upward migration of fluid substrate matter (bubble) can lead to ousting of the hot water/gas near the ground surface and cause an earthquake (EQ) itself in the strength-weakened area; 2. Thus, time and place of the bubble appearance could be random values, but EQ, geochemistry anomaly and foreshocks (seismic, SA and ULF electromagnetic ones) are casually connected; 3. Atmospheric perturbation of temperature and density could follow preseismic hot water/gas release resulting in generation of atmospheric gravity waves (AGW) with periods in a range of 6–60min; 4. Seismo-induced AGW could lead to modification of the ionospheric turbulence and to the change of over-horizon radio-wave propagation in the atmosphere, perturbation of LF waves in the lower ionosphere and ULF emission depression at the ground.
- Published
- 2004
44. Middle latitude LF (40 kHz) phase variations associated with earthquakes for quiet and disturbed geomagnetic conditions
- Author
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Masashi Hayakawa, O. A. Molchanov, Alexander Rozhnoi, and Maria Solovieva
- Subjects
Geophysics ,Amplitude ,Earth's magnetic field ,Geochemistry and Petrology ,Ionospheric perturbations ,Middle latitudes ,QUIET ,Phase (waves) ,Sensitivity (electronics) ,Signal ,Seismology ,Geology - Abstract
The phase (P) and amplitude (A) anomalies in subionospheric LF signal (40 kHz) along the path Japan–Kamchatka of 2300 km have been studied for the data observed by means of a digital OminiPAL receiver for 2 years. The empirical model of background P and A daily variations for quiet and disturbed geomagnetic conditions in the absence of seismic activity is developed. We pay special attention to the P and A features during large magnetic storms. A sensitivity threshold of LF signal to deforming influence of the geomagnetic and seismic factors is defined. Two cases of bay-like behavior of LF phase and amplitude in nighttime are described as a clear earthquake precursor of LF signal. We have found from the statistical study that LF signal effect is observed only for earthquakes with M⩾5.5 and we discuss the possible mechanisms of the effect.
- Published
- 2004
45. Meteorological effects in the lower ionosphere as based on VLF/LF signal observations
- Author
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Alexander Rozhnoi, Viktor Fedun, Maria Solovieva, Masashi Hayakawa, and B. Levin
- Subjects
lcsh:GE1-350 ,Atmospheric pressure ,lcsh:QE1-996.5 ,lcsh:Geography. Anthropology. Recreation ,Low frequency ,Atmospheric sciences ,lcsh:TD1-1066 ,Wind speed ,Latitude ,lcsh:Geology ,Amplitude ,lcsh:G ,Typhoon ,General Earth and Planetary Sciences ,Environmental science ,lcsh:Environmental technology. Sanitary engineering ,Ionosphere ,Tropical cyclone ,lcsh:Environmental sciences - Abstract
Very low and low frequency (VLF/LF) data recorded in the Far Eastern stations Petropavlovsk-Kamchatsky (158.92° E, 53.15° N), Yuzhno-Sakhalinsk (142.75° E, 46.95° N) and Yuzhno-Kurilsk (145.861° E, 44.03° N) are investigated to study the meteorological effects in the lower ionosphere. The results demonstrate the sensitivity of the VLF/LF signals to the variations of atmospheric pressure, humidity, wind velocity and temperature, and the VLF/LF record at the station of Yuzhno-Kurilsk is found to be most sensitive to those variations of atmospheric parameters. The region under consideration is characterized by high winter cyclonic activity in mid-latitudes and strong summer and autumn typhoon activity in low latitudes. VLF/LF signal variations during eight tropical cyclones (TCs) with different intensity are considered. Negative nighttime anomalies in the signal amplitude that are most probably caused by TC activity are found for six events. Those anomalies are observed during 1–2 days when TCs move inside the sensitivity zones of the subionospheric paths. Perturbations of the VLF signal observed during two TCs can be caused by both the TC influence and seismic activity, but no correlation between TC intensity and magnitude of the signal anomalies is found. Spectral analysis of the typhoon-induced disturbed signals revealed the fluctuations with time periods in the range of 7–16 and 15–55 min that corresponds to the range of internal gravity waves periods.
- Published
- 2014
46. Low frequency signal spectrum analysis for strong earthquakes
- Author
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Pier Francesco Biagi, Maria Solovieva, Alexander Rozhnoi, Masashi Hayakawa, and Konrad Schwingenschuh
- Subjects
Geomagnetic storm ,021110 strategic, defence & security studies ,Wave propagation ,lcsh:QC801-809 ,0211 other engineering and technologies ,02 engineering and technology ,lcsh:QC851-999 ,Low frequency ,010502 geochemistry & geophysics ,01 natural sciences ,Spectral line ,lcsh:Geophysics. Cosmic physics ,Geophysics ,Amplitude ,VLF/LF signal propagation. eartquake precursors ,lcsh:Meteorology. Climatology ,Very low frequency ,Ionosphere ,Aftershock ,Geology ,Seismology ,0105 earth and related environmental sciences - Abstract
We examined changes in the spectral composition of the low frequency (LF) subionospheric signals from the NRK transmitter (37.5 kHz) in Iceland that were received in Bari (Italy) relative to the earthquake that occurred in L’Aquila on April 6, 2009. In our previous studies, we have reported the occurrence of preseismic night-time anomalies using observations from three receivers located in Bari, Graz (Austria) and Moscow (Russia). The strongest anomalies in the signals were observed in the NRK-Bari propagation path during the period 5-6 days before the L’Aquila earthquake, as well as during the series of aftershocks. During this period, similar very low frequency (VLF)/LF amplitude anomalies were also observed along several other propagation paths that crossed the L’Aquila seismogenic zone. Spectral analysis of the LF signals filtered in the frequency range 0.28 mHz to 15 mHz shows differences in the spectra for seismo-disturbed days when compared to those for either quiet or geomagnetically disturbed days. These spectral anomalies, which are only observed in the propagation path between NRK and Bari, contain signals with periods of about 10 min to 20 min. These periodic signals are absent both in the spectra of the undisturbed signals for the control paths, and in the spectra of the signals received during geomagnetic storms. The same changes in the spectral composition were observed in the analysis of LF (40 kHz) signals from the JJY transmitter in Japan that were received in Petropavlovsk-Kamchatsky (Russia) during the occurrence of three strong earthquakes with M ≥7.0. The results of this study support the theoretical prediction that the possible mechanism for energy penetration from the origin of an earthquake through the atmosphere and into the ionosphere is based on the excitation and upward propagation of internal gravity waves.
- Published
- 2012
47. Ionospheric turbulence from ground-based and satellite VLF/LF transmitter signal observations for the Simushir earthquake (November 15, 2006)
- Author
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Alexander Rozhnoi, Konrad Schwingenschuh, Masashi Hayakawa, Pier Francesco Biagi, Maria Solovieva, Michel Parrot, Schmidt United Institute of Physics of the Earth [Moscow] (IPE), Russian Academy of Sciences [Moscow] (RAS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), University of Electro-Communications [Tokyo] (UEC), Dipartimento di Fisica, Università degli studi di Bari Aldo Moro (UNIBA), Space Research Institute of Austrian Academy of Sciences (IWF), and Austrian Academy of Sciences (OeAW)
- Subjects
010504 meteorology & atmospheric sciences ,[SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph] ,0211 other engineering and technologies ,02 engineering and technology ,lcsh:QC851-999 ,Low frequency ,01 natural sciences ,Signal ,Seismic risk ,Very low frequency ,0105 earth and related environmental sciences ,021110 strategic, defence & security studies ,Wave propagation ,lcsh:QC801-809 ,Transmitter ,VLF/LF signal propagation ,lcsh:Geophysics. Cosmic physics ,Eartquake precursors ,Geophysics ,Amplitude ,QUIET ,Wave propagation, Seismic risk, VLF/LF signal propagation, Eartquake precursors ,lcsh:Meteorology. Climatology ,Satellite ,Geology ,Seismology - Abstract
International audience; Signals from very low frequency (VLF)/ low frequency (LF) transmitters recorded on the ground station at Petropavlovsk-Kamchatsky and on board the French DEMETER satellite were analyzed for the Simushir earthquake (M 8.3; November 15, 2006). The period of analysis was from October 1, 2006, to January 31, 2007. The ground and satellite data were processed by a method based on the difference between the real signal at night-time and the model signal. The model for the ground observations was the monthly averaged signal amplitudes and phases, as calculated for the quiet days of every month. For the satellite data, a two-dimensional model of the signal distribution over the selected area was constructed. Preseismic effects were found several days before the earthquake, in both the ground and satellite observations.Nombre de références
- Published
- 2012
48. Ionospheric perturbations associated with two huge earthquakes in Japan, using principal component analysis for multiple subionospheric VLF/LF propagation paths
- Author
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Kenji Ohta, Alexander Rozhnoi, O. A. Molchanov, Masashi Hayakawa, Y. Kasahara, Maria Solovieva, Yasuhide Hobara, Y. Ida, and Yuya Ono
- Subjects
Signal processing ,Ionospheric perturbations ,Earthquake prediction ,Transmitter ,lcsh:QC801-809 ,lcsh:QC851-999 ,lcsh:Geophysics. Cosmic physics ,Geophysics ,Amplitude ,Ionospheric perturbations, Earthquakes, Subionospheric VLF/LF propagation, Principal compornent analysis, Earthquake prediction ,Principal component analysis ,lcsh:Meteorology. Climatology ,Geology ,Seismology - Abstract
The presence of ionospheric perturbations in possible association with two huge earthquakes (Noto-hanto peninsula and Niigata-chuetu-oki earthquakes) in 2007 was studied on the basis of a conventional statistical study for a particular propagation path from the JJI transmitter in Miyazaki, Kyushu, to Moshiri in Hokkaido. This is based on automatic routine-based signal processing, in which the trend as the average nighttime amplitude is significantly decreased, with almost simultaneous significant enhancement in the night-time fluctuation as the night-time integration of negative fluctuation from the average. It is, however, shown that this routine-based signal analysis sometime suffers from artificial (or man-made) effects. Thus, in this study, we propose an additional use of principal component analysis (PCA) for simultaneous observation of a few VLF/LF propagation paths. With the application of this PCA method to multi-path data, the artificial effects can be reasonably removed, and also only the geophysical effects associated with earthquakes are detected, by focusing mainly on the third principal component. The satisfactory separation of the principal components is made possible by pre-analysis of the VLF data (extraction from the raw data of the average over a whole year). This PCA method enables us to identify the seismogenic effects in association with earthquakes with smaller magnitudes, down to M 5.5 or M 5.0.
- Published
- 2012
49. Investigations of lower atmospheric trends over Europe with very low frequency wave propagation paths
- Author
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Maria Solovieva, D. Wolbang, Manfred Stachel, Gustav Prattes, C. Grill, Konrad Schwingenschuh, Alexander Rozhnoi, Irmgard Jernej, P. F. Biagi, S. Zehetleitner, Bruno P. Besser, Tommaso Maggipinto, Ö. Aydogar, and H. U. Eichelberger
- Subjects
Amplitude ,Wave propagation ,Atmospheric wave ,Waveguide (acoustics) ,Geophysics ,Earth–ionosphere waveguide ,Very low frequency ,Ionosphere ,Atmospheric sciences ,Geology ,Term (time) - Abstract
In this paper we present results obtained from more than two years continuous very low frequency (VLF) measurements between a network of VLF transmitters and receivers. The focus is on VLF amplitude and phase variations in the Earth lithosphere-ionosphere cavity with the scientific objective to characterise long term trends possibly related to planetary waves and climatological factors. After considering the nominal diurnal and seasonal behaviour of the individual paths in the VLF waveguide, we distinguish between natural and artifical disturbances on different temporal and spatial scales. We conclude that it is too early to speak of a clear trend, but VLF investigations together with complementary measurements can be a useful tool in long term environmental and climatological studies on medium spatial scales.
- Published
- 2012
50. A statistical study on the correlation between lower ionospheric perturbations as seen by subionospheric VLF/LF propagation and earthquakes
- Author
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Maria Solovieva, Takashi Nakamura, Yasuhide Hobara, Masashi Hayakawa, S. Maekawa, Y. Kasahara, Francesco Muto, Alexander Rozhnoi, T. Horie, and O. A. Molchanov
- Subjects
Correlation ,Electromagnetics ,Amplitude ,Anomaly (natural sciences) ,Physics::Space Physics ,Magnitude (mathematics) ,Dispersion (water waves) ,Seismology ,Seismic wave ,Geology ,Standard deviation ,Physics::Geophysics - Abstract
The subionospheric VLF/LF propagation is extensively used to investigate the lower ionospheric perturbation in possible association with earthquakes. An extensive period of data over seven years from January 2001 to December 2007 and a combination of different propagation paths in and around Japan are used to examine the statistical correlation between the VLF/LF propagation anomaly (average nighttime amplitude, dispersion and nighttime fluctuation) and earthquakes with magnitude greater than 6.0. It is then found that the propagation anomaly exceeding the 2σ (standard deviation) criterion indicating the presence of ionospheric perturbation is significantly correlated with earthquakes with shallow depth (
- Published
- 2011
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