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Hayakawa M.,University of Electro - Communications | Hayakawa M.,Hayakawa Institute of Seismo Electromagnetics Co. | Hayakawa M.,Analysis Inc. | Kasahara Y.,University of Electro - Communications | And 3 more authors.
Journal of Geophysical Research: Space Physics | Year: 2012

The Doppler-shift observation of LF (f = 60 kHz) subionospheric signal from Saga (Kyushu) (with call sign of JJY) as observed at Chofu (CHF), has been used to investigate the properties of ionospheric perturbations possibly associated with earthquakes(EQs). The period of analysis is seismo-active half a year from January 1, 2009 to June 30, 2009, and six EQs with magnitude greater than 5.0 (in a range from 5.1 to 5.8, which took place within the wave sensitive area of the JJY-CHF path) are dealt with. It is found from the Doppler-shift observation at CHF that the Doppler shifts are really observed and the components in the frequency ranges of AGW (atmospheric gravity wave) and AW (acoustic wave) in the Doppler shifts are clearly enhanced, at least, before each EQ. This observational fact would lend a strong support to the important role of atmospheric oscillation channel in the lithosphere-atmosphere-ionosphere coupling mechanism. ©2012. American Geophysical Union. All Rights Reserved.

Hayakawa M.,University of Electro - Communications | Hayakawa M.,Hayakawa Institute of Seismo Electromagnetics Co. | Hayakawa M.,Analysis Inc. | Rozhnoi A.,Russian Academy of Sciences | And 5 more authors.
Geomatics, Natural Hazards and Risk | Year: 2013

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. © 2013 Copyright Taylor and Francis Group, LLC.

Hayakawa M.,University of Electro - Communications | Hayakawa M.,Hayakawa Institute of Seismo Electromagnetics Co. | Hayakawa M.,Analysis Inc. | Hobara Y.,University of Electro - Communications | And 6 more authors.
Terrestrial, Atmospheric and Oceanic Sciences | Year: 2013

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.

Ida Y.,University of Electro - Communications | Yang D.,China Earthquake Administration | Li Q.,China Earthquake Administration | Sun H.,China Earthquake Administration | And 3 more authors.
Nonlinear Processes in Geophysics | Year: 2012

The long-term data (during the period of 1 March 2003 through 31 December 2006) of ULF geomagnetic variations observed at Kashi station (geographic coordinates: 39.5° N, 76.0° E) in China have been used to investigate the long-term variation of fractal dimension of ULF emissions. We have studied the changes in fractal dimension in association with several earthquakes around the observation station. It is then found that a significant change (or decrease) in the fractal dimension of the Z component took place before the 1 September 2003 earthquake, which lends a further support to our previous finding based on our improved polarization analysis for the same earthquake. The results obtained are discussed in the contexts of a few aspects (detectability of seismogenic emissions, comparison with previous results by other analysis methods, the importance of fractal analysis in the nonlinear process of the lithosphere and earthquake prediction). © 2012 Author(s).

Nickolaenko A.P.,Ukrainian Academy of Sciences | Hayakawa M.,Hayakawa Institute of Seismo Electromagnetics Co. | Hayakawa M.,University of Electro - Communications
Radio Science | Year: 2014

Spectra and the waveforms are computed of the pulsed radio signals arriving from different distances to an observer in the Earth-ionosphere cavity with the single-scale exponential profile of air conductivity. The data were obtained for the cavity with exceptionally small losses. Spectra are compared of the signals in the realistic and an idealistic Earth-ionosphere cavities. The waveforms are computed for such cavities and the pulse propagation velocities are evaluated. Studies of the Schumann resonance started from the ideal cavity model. Subsequent works dealt with the realistic propagation parameters and the ionosphere models on the Earth and other planets. However, the case of small losses is missing in the literature. We model ELF radio signals in such a cavity and demonstrate their noticeable distinctions from the customary records. In particular, the sinusoidal signals do not appear in the cavity with small losses, and instead, we obtain the sharp and large pulses. Computations show that the waveform propagating in the spherical cavity expands in time and reduces in amplitude. The time domain pulsed amplitudes were found at the source antipode and at the source point for the round-the-world wave. The latter becomes rather small even in the cavity with minor losses, so that autotriggering is unrealistic of a consecutive lightning discharge by the round-the-world echo even in a cavity with minor losses. Key Points ELF waveforms are computed in the Earth-ionosphere cavity with small losses ©2014. American Geophysical Union. All Rights Reserved.

Ohta K.,Chubu University | Izutsu J.,Chubu University | Schekotov A.,Russian Academy of Sciences | Hayakawa M.,University of Electro - Communications | And 2 more authors.
Radio Science | Year: 2013

The ULF/ELF short-term electromagnetic precursor is discovered for the disastrous Japan earthquake (EQ) occurred on 11 March 2011. This analysis is based on the records measured by search coil magnetometers located at Nakatsugawa (geographic coordinates; 35.42°N, 137.55°E), Shinojima (34.67°N, 137.01°E), and Izu (34.64°N, 137.01°E) of the Chubu University network. The data of these magnetometers are extensively used to analyze the ULF/ELF seismo-atmospheric radiation. It is then found that the ULF/ELF atmospheric radio emission is reliably detected on 6 March before the main shock on 11 March, probably as a precursory signature of the EQ. Further confirmation on its seismic origin was provided by the observational fact that the azimuths of the radiation source from all observation sites coincide approximately with the region of the forthcoming EQ. Key Points The ULF/ELF electromagnetic radiation before the 2011 3.11 Japanese earthquake ©2013. American Geophysical Union. All Rights Reserved.

Solovieva M.,Russian Academy of Sciences | Rozhnoi A.,Russian Academy of Sciences | Fedun V.,University of Sheffield | Schwingenschuh K.,Austrian Academy of Sciences | And 2 more authors.
Annals of Geophysics | Year: 2015

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. © 2015 by the Istituto Nazionale di Geofisica e Vulcanologia. All rights reserved.

Nickolaenko A.P.,Ukrainian Academy of Sciences | Hayakawa M.,Hayakawa Institute of Seismo Electromagnetics Co. | Hayakawa M.,University of Electro - Communications
Geomatics, Natural Hazards and Risk | Year: 2014

The impact of seismogenic ionosphere non-uniformity is considered on the Schumann resonance (SR) signals observed both in the vertical electric and two orthogonal horizontal magnetic field components. The model is able to interpret the anomalous signals observed in Japan in possible association with the earthquakes (EQs) in Taiwan. Changes in the SR intensity arise from a localized reduction of the ionosphere over the EQ epicentre. Signals in the regular Earth-ionosphere cavity are described by using the knee model of vertical conductivity profile. It is suggested that pre-seismic and seismic activity lowers the knee altitude by 20 km at the centre of disturbance, and the perturbation has the Gaussian radial dependence in the 1 Mm zone. The diffraction problem in the cavity with a localized disturbance is resolved by using the Stratton-Chu integral equation. The data of Optical Transient Detector are used to model the source distribution. A pronounced modification is obtained in the intensity around the fourth mode frequency in a form of abrupt spectral changes. The model data are found to be similar to observations, and properties of the model seismic anomalies are discussed. © 2013 Taylor & Francis.

Galuk Yu.P.,Saint Petersburg State University | Nickolaenko A.P.,Ukrainian Academy of Sciences | Hayakawa M.,Hayakawa Institute of Seismo Electromagnetics Co.
Telecommunications and Radio Engineering (English translation of Elektrosvyaz and Radiotekhnika) | Year: 2015

Investigations remains update of relationship between the parameters of global electromagnetic (Schumann) resonance and characteristics of vertical profile of atmosphere conductivity. We use the rigorous full wave solution of the electrodynamic problem in the spherical Earthionosphere cavity and compare the results with the described in literature heuristic knee model having a single kink. By using parameters of this heuristic model, we constructed vertical profile of atmospheric conductivity and used it in the rigorous full wave solution for the propagation constant of ELF radio waves. Afterwards, the power spectra were computed of vertical electric and horizontal magnetic fields in the framework of the uniform global distribution of the planetary thunderstorm activity. We show that conductivity profile based on the one kink does not match the rigorous full wave solution and the subsequent computations of the power spectra of the Schumann resonance.

Yamaguchi H.,Fuji Security Systems Co. | Hayakawa M.,Analysis Inc. | Hayakawa M.,Hayakawa Institute of Seismo Electromagnetics Co. | Hayakawa M.,Advanced Wireless Communications Research Center
Journal of Asian Earth Sciences | Year: 2015

It is so far believed that ionospheric perturbations as detected by subionospheric VLF/LF (very low frequency/low frequency) propagation, are generated above and around the earthquake (EQ) epicenter. This paper presents very rare cases, which are in complete contrast to the above fact. We have found that in extremely rare cases when EQs happened (i) in the Pacific Ocean or (ii) offshore the Soya cape (Hokkaido) both with very large depths (300-400. km), corresponding ionospheric perturbations take place far away from the EQ epicenter and above the regions with considerable seismic intensity at the time of each EQ. Two EQs happened in the Torishima area of Izu islands (magnitude ~7 and depth ~400. km), and corresponding seismic intensity was observed in the Tokyo and Ibaraki districts. Our VLF data have indicated that the ionospheric perturbation takes place over such regions with high seismic intensity. Another group is two EQs (magnitude ~5) offshore the Soya cape of Hokkaido, and the spatial distribution of seismic intensity at the time of each EQ is just around Aomori prefecture. VLF data have indicated the ionospheric perturbations taken place over the same Aomori area, which is in complete coincidence with the spatial distribution of seismic intensity. As a conclusion, these exceptional examples are, in principle, very similar to the concept of 'selectivity' (or sensitive zone) of geoelectric measurement by the Greek group, and we try to interpret these cases in the context of lithosphere-atmosphere-ionosphere coupling. © 2014 Elsevier Ltd.

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