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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.

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 (

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.

The purpose of this paper is to discuss the lithosphere–atmosphere–ionosphere coupling (LAIC) effects with the use of multiparameter precursor observations for two successive Japanese earthquakes (EQs) (with a magnitude of around 7) in February and March 2021, respectively, considering a seemingly significant difference in seismological and geological hypocenter conditions for those EQs. The second March EQ is very similar to the famous 2011 Tohoku EQ in the sense that those EQs took place at the seabed of the subducting plate, while the first February EQ happened within the subducting plate, not at the seabed. Multiparameter observation is a powerful tool for the study of the LAIC process, and we studied the following observables over a 3-month period (January to March): (i) ULF data (lithospheric radiation and ULF depression phenomenon); (ii) ULF/ELF atmospheric electromagnetic radiation; (iii) atmospheric gravity wave (AGW) activity in the stratosphere, extracted from satellite temperature data; (iv) subionospheric VLF/LF propagation data; and (v) GPS TECs (total electron contents). In contrast to our initial expectation of different responses of anomalies to the two EQs, we found no such conspicuous differences of electromagnetic anomalies between the two EQs, but showed quite similar anomaly responses for the two EQs. It is definite that atmospheric ULF/ELF radiation and ULF depression as lower ionospheric perturbation are most likely signatures of precursors to both EQs, and most importantly, all electromagnetic anomalies are concentrated in the period of about 1 week–9 days before the EQ to the EQ day. There seems to exist a chain of LAIC process (cause-and-effect relationship) for the first EQ, while all of the observed anomalies seem to occur nearly synchronously in time for the send EQ. Even though we tried to discuss possible LAIC channels, we cannot come to any definite conclusion about which coupling channel is plausible for each EQ.

The method of critical fluctuations (MCF) is a time series analysis method which provides a way of both identifying the critical state and the departure from it. Its application to the ground-based ultra-low frequency (ULF) magnetic field fluctuations observed prior to the very strong earthquakes (EQs) of magnitudes M W = 6 . 2 , M W = 6 . 0 and M W = 7 . 0 which sequentially took place within a two days period (April 14–15, 2016) in Southwest Japan under the city of Kumamoto reveals when the underlying process reached critical state, as well as when it departed from critical state. Specifically, critical dynamics was identified in the raw total geomagnetic field intensity (F) ULF recordings of the Kanoya (Japan) station ∼ 4 d before the M W = 6 . 2 and ∼ 5 d before the M W = 7 . 0 event. Moreover, the progressive development of the symmetry breaking phenomenon, which signifies departure from critical state, was identified in later recordings. Specifically the phenomenon evolved from a few hours before the M W = 6 . 0 event until a few hours after the occurrence of the specific EQ, which was a few hours before the M W = 7 . 0 event. The detected combination of phenomena, i.e., the detection of critical state followed by the detection of the departure from the critical state by means of symmetry breaking, indicates that the main event was the third and strongest EQ, while the two preceding EQs were strong foreshocks.

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 (

On 15 April 2016 a very strong and shallow earthquake (EQ) ( M W = 7.0 , depth ∼ 10 km) occurred in Southwest Japan under the city of Kumamoto, while two very strong foreshocks ( M W = 6.2 and M W = 6.0 ) preceded by about one day. The Kumamoto EQs being very catastrophic, have already attracted much attention among the scientific community in a quest for understanding the generation mechanism, as well as for reporting any preseismic anomalies in various observables and assessing the effectivity of the current early warning systems. In the present article we report precursory behavior of the ground-based observed ultra-low frequency (ULF) magnetic field variations before the Kumamoto EQs. By analyzing specific ULF magnetic field characteristics in terms of the recently introduced natural time (NT) analysis method, we identified that ULF magnetic field variations presented critical features from 2 weeks up to 1 month before the Kumamoto EQs. Specifically, the ULF magnetic field characteristics F h , F z , D h and δ D e p were analyzed. The first two represent variations of the horizontal and vertical components of the geomagnetic field. The third and fourth characteristics correspond to the depression (decrease) and a relative depression of the horizontal magnetic field variations, respectively. The latter depends on the degree of ionospheric disturbance. All of them were found to reach criticality before the Kumamoto EQs; however, in different time periods for each characteristic.

The authors would like to make the following corrections to this paper [...]

Anomalies in Schumann resonance (SR) (or global electromagnetic ELF (extremely low frequency) resonance due to global lightning activity in the Earth-ionosphere cavity) attract lot of attention in possible association with earthquakes (EQs). The first anomalies were observed in Japan for EQs in Taiwan when the distance between observatory and the EQ epicenter was a few Mm (1 Mm = 1000 km). Recently, Hayakawa et al. (2019, 2020a, b) have suggested a new SR anomaly related to the nearby (a few hundred km) EQs unlike the previous distant EQs. This paper presents the SR anomalies observed in the vicinity of Nagoya-city for two relatively close (∼1000 km) successive EQs of the magnitude around 7 that occurred offshore the Tohoku prefecture in Japan. The anomaly is characterized by the enhancement in amplitudes of SR modes, and this abnormal behavior was detected before and after each of the two EQs. Observational data were interpreted using the seismogenic perturbations of the lower ionospheric conductivity. Model computations imply the full wave solution of ELF electromagnetic problem in form of Riccati equation and the 2D telegraph equations. We show that observed anomalous alterations in the SR spectra might be attributed to two types of seismogenic modifications: the compression or the expansion of the vertical profiles of mesosphere conductivity over the EQ epicenter.

The Kumamoto area of Kyusyu Island was attacked by a series of large earthquakes (EQs) in April, 2016. The first two foreshocks had the magnitudes of 6.5 and 6.4, and about 1 day later there was the main shock on 15 April (UT) with magnitude 7.3. These are fault-type EQs, and so we would expect a variety of electromagnetic precursors to these EQs because we had detected different phenomena for the 1995 Kobe EQ, same fault-type EQ. As for the lithospheric effect, the ULF data at Kanoya observatory (about 150 km from the EQ epicenters) are used, but the simple statistical analysis could not provide us with any clear evidence of ULF radiation from the lithosphere. However, our conventional analyses indicated clear signatures in the atmosphere as ULF/ELF impulsive emissions and also in the ionosphere as observed by means of VLF propagation anomalies and ULF depression. ULF/ELF radiation appeared on 8-11 April (in UT) (maximum on 10 and 11 April (UT)), while ULF depression took place on 8 and 10 April (in UT), so that both atmospheric radiation and ionospheric perturbation took place nearly during the same time period.

This paper reports an attempt to use ultra-low-frequency (ULF) magnetic field data from a space weather monitoring magnetometer array in the study of earthquake (EQ) precursors in Greece. The data from four magnetometer stations of the HellENIc GeoMagnetic Array (ENIGMA) have been analyzed in the search for possible precursors to a strong EQ that occurred south of Lesvos Island on 12 June 2017, with magnitude Mw = 6.3 and focal depth = 12 km. The analysis includes conventional statistical methods, as well as criticality analysis, using two independent methods, the natural time (NT) method and the method of critical fluctuations (MCF). In terms of conventional statistical methods, it is found that the most convincing ULF precursor was observed in the data of ULF (20&ndash, 30 mHz) depression (depression of the horizontal component of the magnetic field), which is indicative of lower ionospheric perturbation just 1 day before the EQ. Additionally, there are indications of a precursor in the direct ULF emission from the lithosphere 4 days to 1 day before the EQ. Further study in terms of NT analysis identifies criticality characteristics from 8 to 2 days before the EQ both for lithospheric ULF emission and ULF depression, while MCF reveals indications of criticality in all recorded magnetic field components, extending from 10 to 3 days before the EQ. Beyond the recordings of the geomagnetic stations of ENIGMA, the recordings of the fracto-electromagnetic emission stations of the HELlenic Seismo-ElectroMagnetics Network (ELSEM-Net) in Greece have been analyzed. The MHz recordings at the station that is located on Lesvos Island presented criticality characteristics (by means of both NT analysis and MCF) 11 days before the EQ, while a few days later (7&ndash, 6 days before the EQ), the kHz recordings of the same station presented tricritical behavior. It is noted that the magnetosphere was quiet for a period of two weeks before the EQ and including its occurrence.

The study was carried out to evaluate velocity of development of fibrosis of liver in patients with chronic hepatitis C using laboratory tests. The sampling of 150 patients with chronic hepatitis C were examined to analyze blood serum in phase of reactivation detecting concentration of hyaluronic acid, alpha-fetoprotein, iron, ferritin, vascular endothelial risk factor, malonic dialdehyde and activity of catalase. The degree of fibrosis of liver was evaluated using technique of ultrasound elastography. The velocity of development of fibrosis of liver was calculated as ratio of fibrosis (in points) to duration of infection (in years). The velocity of development of fibrosis of liver in group with slow rate of progression of disease made up in average 0.01±0.04 points per year and in the group with fast rate of progression of chronic hepatitis C - 0.45±0.34 points per year (p0.001). In the group of patients with high velocity of development of fibrosis of liver were registered reliably higher values of density of liver (p0.001). The fast velocity of development of fibrosis of liver was accompanied by increasing of serum concentrations of hyaluronic acid (p0.001), alpha-fetoprotein (p=0.04), iron (p=0.03), ferritin (p=0.03) and decreasing of activity of catalase (p=0.04). The correlation analysis substantiated availability of reliable direct relationships of rate of progression of fibrosis with duration of disease (r=0.27, p=0.01), density of liver (r=0.86; p0.001), hyaluronic acid (r=0.59; p0.001), alpha-fetoprotein (r=0.23; p=0.04), ferritin (r=0.23; p=0.04), vascular endothelial risk factor (r=0.21; p=0.04). The association of increased serum levels of hyaluronic acid, alpha-fetoprotein, vascular endothelial risk factor, iron, ferritin and low activity of catalase with fast velocity of development of fibrosis of liver can be recommended as additional criteria of evaluation of rate of progression of fibrosis under chronic hepatitis C.