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Electromagnetic emissions (EMEs) associated with earthquake (EQ) epicenters are found to be one of the most reliable phenomena for the short-term pre-seismic mechanism of earthquakes. The detection mechanism of such emissions can have both direct and indirect techniques. In this manuscript, we attempted to present the signature of such emissions before two strong EQs, one in Fukushima on November 21, 2016, and another in Kumamoto on April 15, 2016, in Japan. We use the lithospheric emission in the range of ultra-low frequency (ULF) waves as observed from the Kakioka observatory in Japan for direct measurement. For the indirect investigation, we use the concept of energetic particle precipitation in the inner radiation belt due to wave–particle interaction through the pitch angle scattering processes. We use the particle enhancement (electron and proton) observed from the space-based National Oceanic and Atmospheric Administration (NOAA) satellites. The ULF results found an abnormal increase in lithospheric radiation for Kumamoto and Fukushima EQs on three days and ten days before the EQs, respectively, and an ionospheric depression on six days before both the cases. The satellite observations related to the EMEs from these EQs exhibit electron particle bursts (PB) on the day of the Fukushima EQ. We observe particle bursts 4–5 and 10 days before the mainshock for the Kumamoto EQ. We are not found any proton precipitation for the Fukushima EQ where signatures of proton count number are observed for the Kumamoto EQ. This type of simultaneous observation from the ground and satellite-based instruments establishes that EMEs are observed before the EQs and can be a potential candidate for short-term precursory studies. [ABSTRACT FROM AUTHOR]

The aim of this work is to study the relationship between the pre-earthquake emissions of radon and ULF/ELF (1–30 Hz) atmospheric electromagnetic radiation. The problem is considered on the example of the 2011 Tohoku earthquake. Radon, ionizing air, creates ions—centers of condensation of water vapor. As a result of condensation, heat is generated. It results in growth of air temperature and decrease in its humidity. This phenomenon serves as an indicator of air ionization. We used data from 20 Japan Meteorological Agency (JMA) weather stations located on Honshu Island to estimate any changes in temperature and humidity over ± 20 days from the date of the main shock. At the same time, we monitored the intensity and location of the source of ULF/ELF radiation using three induction magnetometers belonging to Chubu University. We compared the times and locations of observed signs of ionization and electromagnetic radiation to find out their relationship. It turned out that they are independent, since their dates and localizations do not match. In addition, we found intense ionization of the air after March 11 over a large area of Honshu Island, caused by radiative radiation from the nuclear disaster at the Fukushima Daiichi nuclear power plant. However, this phenomenon did not cause low-frequency atmospheric electromagnetic radiation either. These suggest that there is no direct relationship between air ionization and ULF/ELF radiation. This is true at least for this case, given the island nature of the land and oceanic EQs. [ABSTRACT FROM AUTHOR]

In this article, we describe a method for predicting of the epicenter location region of Kamchatka and Commander earthquakes (EQs). It is based on the properties of the precursory atmospheric ULF/ELF (1–30 Hz) radiation and the spatial statistics of local EQs in relation to the Kuril-Kamchatka and Aleutian trenches. From this statistics, it follows that more than 90% of events with magnitude (ML) of more than 5 occur in the gap ~ 150 km west of the Kuril-Kamchatka trench and north-east of the Aleutian trench. Additionally, we obtain the approximate location of the epicenter by determining the position of the radiation source. We suppose that it is caused by gas eruption from the hearth of the EQ to the trench and has the nearest location to the EQ epicenter. Further, we obtain other parameters of supposed position of the epicenter from spatial statistics of EQs relative to the projection of radiation source, which approximately coincides with gas emanation area in the ocean surface. The main drawbacks of the method are the dependence of its accuracy on the industrial interferences and the ambiguity of determining the epicenter location in the case of single-point registration of radiation when the main lobe of the azimuthal distribution of radiation crosses both trenches. [ABSTRACT FROM AUTHOR]

A wide variety of electromagnetic phenomena possibly related with earthquake (EQ) preparation processes have been reported in the literature during the last few decades. An interesting aspect in their study is the time series analysis of the related observables aiming at the investigation of any embedded dynamics. In this review article we focus on the study of fracto-electromagnetic emissions (fracto-EME) at the MHz band, the ultra-low frequency (ULF) magnetic field variations (<3 Hz) and the subionospheric very low frequency (VLF) propagation anomalies. We present recent analysis results for these electromagnetic signals using two independent methods which are known for their ability to uncover critical dynamics, the recently proposed method of critical fluctuations (MCF) and the natural time (NT) analysis method. Our results show that all three considered electromagnetic signals present critical characteristics from a few weeks up to a few days before the main shock occurrence. On the other hand, signatures for the departure from the critical (highly symmetrical) state towards a low symmetry state, a state during which there is high localization of the EQ preparatory process, have been identified in specific cases for the MHz fracto-EME as well as for the ULF magnetic field variations. Based on a multidisciplinary analysis, a four-stage model of EQ dynamics by means of fracto-EME in the MHz and kHz bands has recently been proposed. The hypothesis that the precursors considered in this article emerge during the spatially extensive phase of EQ preparation, which corresponds to the first stage of the abovementioned four-stage model, as well as their relation with the foreshock seismic activity are discussed. [ABSTRACT FROM AUTHOR]

This paper is devoted to a method of short-term earthquake (EQ) prediction in Kamchatka, Russia. Properties of low-frequency magnetic fields are the basics of the method, and we used two seismo-electromagnetic phenomena in the EQ prediction: 1. seismo-ionospheric depression in the frequency range of 0.01–0.1 Hz (ULF depression), 2. seismo-atmospheric radiation in the frequency range of 1–30 Hz (ULF/ELF radiation). It is now generally accepted that gas eruption before an EQ causes these ULF/ELF phenomena. We propose a hypothesis that gas emanates from the area in the bottom of Kuril–Kamchatka or Aleutian trenches closest to the epicenter of a forthcoming EQ. The three parameters of an EQ are (i) when (time), (ii) where (position) a next EQ is coming with (iii) how big (magnitude) in the short-term EQ prediction. Position of the source of atmospheric radiation gives an estimate of the epicenter location. Then, we estimate the local magnitude in consequence of its statistical dependence on ULF depression and epicenter distance. Date of a coming EQ is determined by the statistical dependence of delays of EQs relative to the dates of their precursors. The result of application of this method to real magnetic field data is illustrated by official prediction processes during a period of March–May 2016. Limits and possible errors of the method as well as methods to enhance the reliability of the prediction are discussed. [ABSTRACT FROM AUTHOR]

The fractal characteristics of the ultra-low-frequency (ULF) magnetic field variations recorded prior to the Tohoku earthquake (EQ) with M = 9 which happened on 11 March 2011 are studied in this article with the use of detrended fluctuation analysis and Higuchi fractal dimension algorithm. In the specific study, we use for our calculations only nighttime (LT = 3 a.m. ± 2 h) data because of their lowest contamination by industrial noise. A key aspect of our analysis is the investigation about any possible correlation of the ULF magnetic field variations or their calculated fractal characteristics with geomagnetic indices. Different preprocessing approaches are examined aiming at the minimization of any possible influences from global phenomena in the fractal analysis results, while in the same time retaining the scale-invariant character of ULF magnetic field variations after preprocessing. The obtained fractal analysis results imply locally driven change in the fractal characteristics of the ULF data prior to the Tohoku EQ, which is compatible with the change that has been reported prior to other large EQs. [ABSTRACT FROM AUTHOR]

We present the experimental records of the radio pulse related to the gamma burst that took place on December 27, 2004. The records, which are synchronized by GPS time marks, were obtained in the observatories at Moshiri and Onagawa (Japan), Esrange (Sweden), Karimshino (Kamchatka, Russia), Nagycenk (Hungary), and Hornsund (Polish Polar Station Spitzbergen). The data demonstrate exceptional similarity and contain characteristic pulses that correspond to the time of gamma-ray arrival. Processing of the signals shows that along with the time match, the following modeling predictions are confirmed: radio pulses contain a signal at the main frequency of the Schumann resonance, the field source has positive polarity (the current is directed from the ionosphere towards the Earth), the polarization of the horizontal magnetic field of the radio wave is almost linear, and the directions towards the source indicate the epicenter of the gamma-quanta flux collision with the ionosphere. These properties correspond to the concept of the parametric electromagnetic pulse that is produced due to a significant change in the current in the global electric circuit, which is caused by a cosmic gamma-ray flare. [ABSTRACT FROM AUTHOR]

We compare the experimentally observed and model waveforms of the electromagnetic pulse associated with an abrupt change in the height of the Earth-ionosphere cavity, which was caused by an intense gamma-ray burst that arrived from the cosmic source in December 27, 2004. Polarization and spectral properties of the burst are examined. It is shown that the experimentally observed extremely low frequency (ELF) radio pulse exceeds the level of a regular Schumann-resonance background signal severalfold, and its waveform is close to the calculated one. The wave arrival angle is close to the direction towards the epicenter of the ionospheric disturbance. The time of pulse arrival at the Karymshino observatory (52.83°N, 158.13°E) is about 0.16 s ahead of the burst recording time. [ABSTRACT FROM AUTHOR]

The results of two-year monitoring of the Schumann-resonance signals are processed and the diurnal and seasonal variations in the activity of the global thunderstorm centers are estimated. We calculate the field in the model of thunderstorm activity localized in a small circular area (the model of a single source). Comparison between the experimental and model data allowed us to find the position of the maximum of the global thunderstorm activity. It is shown that a more exact interpretation of the experimental data is achieved if additional background radiation, which remains approximately constant during a day and is approximately equal to the intensity of a compact source, is included into the model. [ABSTRACT FROM AUTHOR]