Masashi Hayakawa

The University of Electro-Communications | UEC · Advanced Wireless & Communication Research Center (AWCC)

We present the atmospheric anomalies instigated through seismogenic sources by a multichannel observation using ground- and satellite-based systems. This study emphasizes the seismic event which happened on the east coast of Japan, near the Fukushima Prefecture on November 21, 2016 (in UTC), with a magnitude of 6.9 and a depth of 11.4 km. We mainly...

We present the first report of global ionospheric disturbances due to the most powerful Gamma Ray Burst GRB221009A occurred on 9 October 2022. Very Low Frequency (VLF) and Low Frequency (LF) sub-ionospheric radio signals are used to diagnose the effect of the GRB on the lower ionosphere. Both daytime and nighttime effects are analyzed in VLF and LF...

Very low frequency (VLF) signals are considered as an important tool to study ionosphere disturbances. We have studied variations in signal amplitude of the Japanese JJI transmitter received by a network of eight Japan stations. The distinctions between characteristics of daytime and nighttime disturbances are considered. Signal processing based on...

In this study, we report atmospheric electric field (AEF) anomalies observed around the time of earthquakes (EQs) in Japan. Using a newly developed AEF observation network with three spatially separated stations in Japan (Chofu, Kakioka, and Iwaki), we conducted a study for two EQs that occurred within a few 100 km from the EQ epicenter under relat...

Lithosphere–atmosphere–ionosphere coupling (LAIC) is studied through various physical or chemical quantities, obtained from different sources, which are observables of the involved complex processes. LAIC has been proposed to be achieved through three major channels: the chemical, the acoustic, and the electromagnetic. Accumulated evidence supporti...

We present the variation of unusual atmospheric parameters, aerosols, to understand the pre-seismic irregularities for two major EQs in Japan. Here, we consider Aerosol Optical Depth and Angstrom Exponent data retrieved from Moderate Resolution Imaging Spectroradiometer (MODIS) instrument onboard TERRA satellite to establish the possible connection...

In this work, we demonstrate the Natural time (NT) analysis of potential energy data that have been computed from temperature profiles that have been obtained from the "sounding atmosphere using broadband emission radiometry" (SABER) instrument, which is a part of a satellite called "thermosphere-ionosphere-mesosphere energetics and dynamics" (TIME...

In this study, we investigate the seasonal variation of sunrise and sunset terminator times of several VLF propagation paths based on 2-year long recordings (2020-2022) from the newly installed VLF/LF receiver UWA, installed in Athens (University of West Attica), by finding their relationship with local sunrise and sunset time. More specifically, i...

A new VLF/LF (10-47.5 kHz) radio receiver, established in 2020 at the University of West Attica (call sign UWA), is continuously monitoring the lower ionosphere, mainly aiming to find pre-seismic indications before earthquakes (EQs), as well as precursors associated with other extreme geophysical and space phenomena. The receiver records signals (a...

A VLF (10-47.5 kHz) radio receiver with call sign UWA has recently been installed at the University of West Attica in Athens (Greece) and is continuously monitoring the lower ionosphere by means of the receptions from many transmitters, in order to identify any possible pre-seismic signatures or other precursors associated with extreme geophysical...

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 be...

Multi-parameter observations, powerful for the study of lithosphere–atmosphere–ionosphere coupling (LAIC), have been performed for a recent Tokyo earthquake (EQ) with a moderate magnitude (M = 5.9) and rather larger depth (~70 km) on 7 October 2021, in the hope of predicting the next Kanto (Tokyo) huge EQ, such as the 1923 Great Kanto EQ (with a ma...

Lower ionospheric perturbation during earthquake activity is well recognized by the anomalous behavior of Very Low or Low Frequency (VLF/LF) radio signal. In this study, we present the sub-ionospheric VLF signal modulation during the Samos earthquake that took place on October 30, 2020 (M = 6.9). We use the conventional terminator time method to ch...

We present results of concurrent observations of anomalous Schumann resonance (SR) signals during the major phase of eruption of Tonga volcano on 15 January 2022. The experimental data were recorded at French, Italian, Russian, and Japanese observatories that monitor natural electromagnetic signals in the ELF and ULF bands. The major phase of erupt...

We simulate numerically the propagation of slow-tail sferics, which occupy a wide frequency band from 1 Hz to 10 kHz, in the spherical Earth–ionosphere cavity. The TM wave generated by a vertical lightning discharge is considered. Classic engineering models of a lightning stroke are employed. The calculations use the Williams stroke model as the fi...

The gross charge distribution in an electrified cloud has already been estimated by polarity distribution of the electrostatic field on the ground surface. While either a dipole or a tripole charge structure is commonly accepted, the increase–decrease and motion of each point charge in those models are both still unclear. This paper presents a new...

Atmospheric disturbances caused by seismic activity are a complex phenomenon. The Lithosphere–Atmosphere–Ionosphere Coupling (LAIC) (LAIC) mechanism gives a detailed idea to understand these processes to study the possible impacts of a forthcoming earthquake. The atmospheric gravity wave (AGW) is one of the most accurate parameters for explaining s...

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

We focus on the possible thermal channel of the well-known Lithosphere–Atmosphere– Ionosphere Coupling (LAIC) mechanism to identify the behavior of thermal anomalies during and prior to strong seismic events. For this, we investigate the variation of Surface Latent Heat Flux (SLHF) as resulting from satellite observables. We demonstrate a spatio-te...

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 geologi...

In this work, we represent the lightning initiation scenario as a sequence of two transitions of discharge activity to progressively larger spatial scales: the first one is from small-scale avalanches to intermediate-scale streamers; and the second one is from streamers to the lightning seed. We postulate the existence of ion production centers in...

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 E...

Citation: Sasmal, S.; Chowdhury, S.; Kundu, S.; Politis, D.Z.; Potirakis, S.M.; Balasis, G.; Hayakawa, M.; Chakrabarti, S.K. Pre-Seismic Irregularities during the 2020 Samos (Greece) Earthquake (M = 6.9) as Investigated from Multi-Parameter Approach by Ground and Space-Based Techniques. Atmosphere 2021, 12, 1059. https://doi.

The propagation of natural wide-band pulsed radio signals in the spherical Earth – ionosphere cavity is numerically simulated. The frequency band considered is 1–10,000 Hz. We address the TM waves originated from a vertical lightning stroke of the Bruce and Golde, Williams, or Jones model. Major data are based on the Williams’ lightning model. The...

We address deviations in the source bearing of natural pulsed extremely low frequency (ELF) radio signals (Q-bursts) in the Schumann resonance band. The model of smooth day – night non-uniformity is used. The observer is located at the Ukrainian Antarctic station “Akademik Vernadsky” (65.25° S and 64.25° W), and the source is positioned at the same...

In this work we present the statistical and criticality analysis of the very low frequency (VLF) sub-ionospheric propagation data recorded by a VLF/LF radio receiver which has recently been established at the University of West Attica in Athens (Greece). We investigate a very recent, strong (M6.9), and shallow earthquake (EQ) that occurred on 30 Oc...

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....

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...

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...

Very Low Frequency (VLF) remote sensing technique is used to probe the D-layer modeling for which we use a very conventional model known as Wait s 2-component iono-spheric model. This model is characterized by two iono-spheric parameters which are 'steepness parameter' (β) and 'effective reflection height' (h). International Reference Ionosphere (I...

Sub-Ionospheric Very Low Frequency (VLF) radio wave propagation characteristics are the major tool to study the lower ionospheric heights mainly D-region. Wait’s 2-component exponential model is a well-known mechanism to understand the basic characteristics of this layer based on VLF remote sensing. This model deals with two major ionospheric param...

A significant anomaly in the extremely low frequency (ELF) spectra of Schumann resonance (SR) was discovered for the 1999 Chi‐Chi earthquake (EQ) in Taiwan as observed in Japan. Similar phenomena were confirmed for other EQs remote from the observer by a few megameters. An additional effect was detected for nearby EQs. The anomalies were explained...

Study of seismo-ionospheric coupling mechanism demands the quiet geomagnetic condition to eliminate any kind of contamination in the lower atmospheric and ionospheric parameters. In this manuscript, we present the effect of back to back two geomagnetic storms before a strong earthquake happened in Imphal, India on January 4, 2016 (M = 6.7). We stud...

Transient luminous events (TLEs) such as sprites, blue jets (BJs) and elves have been studied intensively during the last three decades, and much is now known of their properties. This progress is caused by several factors including satellite optical observations, ground-based measurements of sprite-produced electromagnetic fields, the use of high-...

Using a numerical model of the ELF radio wave scattering by seismogenic localized non-uniformity, we evaluate the earthquake (EQ) magnitude by using modifications in the power spectra of global electromagnetic (Schumann) resonance. The ionosphere non-uniformity is introduced as a disturbance in the vertical profile of atmosphere conductivity above...

In order to have further evidence of the atmospheric oscillation channel of the lithosphere-atmosphere-ionosphere coupling (LAIC), we have studied criticality in global navigation satellite system (GNSS) surface deformation as a possible agent for exciting atmospheric gravity waves (AGWs) in the atmosphere and GNSS fluctuations in the frequency ran...

Ionospheric anomalies possibly related to significant earthquakes (EQs) have been extensively investigated in recent years and could be considered promising for short-term EQ prediction. In this work, we study the subionospheric propagation data recorded during a time period of 3 years (1/1/2014–28/02/2017) by a network of 8 VLF/LF receivers deploy...

The precursory atmospheric gravity wave (AGW) activity in the stratosphere has been investigated in our previous paper by studying an inland Kumamoto earthquake (EQ). We are interested in whether the same phenomenon occurs or not before another major EQ, especially an oceanic EQ. In this study, we have examined the stratospheric AGW activity before...

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-atmospher...

The purpose of this article is to attract the attention of the scientific community to atmospheric gravity waves (GWs) as the most likely mechanism for the transfer of energy from the surface layers of the atmosphere to space heights and describe the channel of seismic-ionospheric relations formed in this way. The article begins with a description...

We propose a scenario in which elevated ionic conductivity regions (EICRs) with dimensions of the order of 0.1–1 m are formed in the turbulent thundercloud environment. The starting point in this scenario is the occurrence of electron avalanches in the vicinity of colliding hydrometeors, leading to the formation of ion production centers. Their dim...

Objective and purpose of the work. We model disturbances in amplitude spectra of vertical electric and horizontal magnetic field components of the signals of global electromagnetic (Schumann) resonance by a seismogenic non-uniformity of the middle atmosphere. The point field source is used positioned at S-E Asia, Africa, or S. America. Observer is...

There has been an enormous progress in the field of electromagnetic phenomena associated with earthquakes (EQs) and EQ prediction during the last three decades, and it is recently agreed that electromagnetic effects do appear prior to an EQ. A few phenomena are well recognizedas being statistically correlated with EQs: one is the lithospheric radio...

The hourly data of the vertical Z and the horizontal H components of 37 ground–based DC–ULF geomagnetic stations are examined during 20 April–12 May 2008. On 9 May 2008, three days before the Wenchuan MS 8.0 shock, anomalies — a double low-point and a decreased amplitude — are registered on the curves of the Z component at 25 stations in a large-sc...

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 o...