Ionospheric Precursors Of Earthquakes Research Articles

Identification of Possible Short-Term Ionospheric Earthquake Precursors for Seismic Events with Intermediate Hypocentrals Depths by Measuring the Standard Parameters of the Mid-Latitude Es Layer

Identification of Possible Short-Term Ionospheric Earthquake Precursors for Seismic Events with Intermediate Hypocentrals Depths by Measuring the Standard Parameters of the Mid-Latitude Es Layer

Driving Source of Change for Ionosphere before Large Earthquake -Vertical Ground Motion-

This paper discusses the relationship between the vertical ground motion and ionospheric disturbances before the Kumamoto earthquake on 16 April 2016, in Kyushu, Japan, using the vertical ground motion measured by slant gauges widely distributed in Kyushu, and the NmF2 observed by ionosondes in Japan and another region. We provide evidence that vertical ground motion excites internal gravity waves (IGWs) that disturb changes in the ionospheric plasma density. From the spectral analysis results of the vertical ground motion data, the summation of various period (frequency) components analyzed from the original data of the slant gauge shows a possible correlation with the change of NmF2 before the earthquake. On the other hand, the influence of the geomagnetic disturbance on vertical ground motion seems to exist. However, we cannot confirm that vertical ground motion is influenced by the geomagnetic disturbance (Kp index) and that the earthquake is triggered by the geomagnetic disturbance. There are two conditions for the vertical ground motion to disturb variations in the ionospheric plasma density: (1) The effective vertical ground motion period should be shorter than 5 h. In addition, (2) vertical ground motion should continue to exist so that wave energy can be continuously injected into the atmosphere. A possible mechanism with which to modify the ionosphere is discussed. The results of this study can provide a basis for the future ionospheric precursors of earthquakes by using the vertical ground motion.

Effectiveness of the Relative δ-Barbier Parameter in the Search for Ionospheric Precursors of Earthquakes

Effectiveness of the Relative δ-Barbier Parameter in the Search for Ionospheric Precursors of Earthquakes

Analysis of Pre-Earthquake Ionospheric Anomalies in the Japanese Region Based on DEMETER Satellite Data

The electron density (Ne), ion density (Ni), and electron temperature (Te) statistics recorded by the DEMETER satellite payload ISL (Instrument Sonde de Langmuir) were used to study the disturbance characteristics of the ionosphere before solid earthquakes of magnitude 6 or higher in Japan during the summer of 2005–2009, to provide more information and methods for the coupling mechanism and short-range earthquake prediction. In this paper, the region of ±10° of the epicenter is divided into 1°×1° pixels, and the background field of each parameter is constructed using data without earthquakes and relatively calm space weather. We also define a measure of the perturbation intensity of ionospheric parameters relative to the background field during the occurrence of earthquakes. The analysis results of the four Japanese earthquakes from space and time show an excellent synchronization in the time and area of the anomalies in ionospheric parameters of the four cases. All four instances showed Ne abnormalities, and three showed Ni and Te anomalies, in which Ne and Ni increased or decreased abnormally, while Te increased abnormally every time, and the anomalies mainly occurred about 9–12 days before the earthquake. This paper eliminates the influence of solar, geomagnetic, and satellite data defects on the experimental results as much as possible in data screening and method selection. The results partially agree with the conclusions reported in the existing literature, and the obtained anomalies are somewhat related to the ionospheric precursors of earthquakes.

Evaluating the Effectiveness of Using Integral Daily Es Characteristics to Identify Short-Term Ionospheric Precursors of Strong Earthquakes

Day-to-day variations of deviations of integral daily characteristics of the sporadic E layer in differentseasons in 1987, 1996, 2003–2004, and 2014 from the reference values are investigated. The analysis isconducted based on hourly measurements from Japanese ground-based vertical ionospheric sounding stationsin order to identify possible short-term ionospheric precursors of crustal (surface) earthquakes withmagnitudes M ≥ 6.5 under real observational conditions. Using the coincidence of the maxima in the variationsof the considered Es characteristics at the same day on pairs of stations located hundreds of kilometersfrom each other, 12 possible ionospheric earthquake precursors (true alarms) and 22 false alarms, which arenot followed by earthquakes of the specified range in different seasons of 1987, 1996, and 2003–2004, werefound. The efficiency of identifying possible short-term ionospheric precursors of strong earthquakes isdetermined by the chosen method based on Hanssen–Kuipers score (Rscore), which turned out to be 0.82 forthe specified time periods. It is concluded that the proposed methodology for identifying short-term ionosphericprecursors of strong earthquakes can be used in real conditions

Ionospheric precursors of strong earthquakes observed using six GNSS stations data during continuous five years (2011–2015)

This study reports the morphological characteristics of anomalous variations in Global Navigation Satellite System Total Electron Content (GNSS-TEC) prior to the strong local earthquakes (EQ) that occurred during the period of 2011–2015. We have analyzed 20 earthquakes of magnitude M ≥ 5.6. A statistical technique is implemented on the data of six GNSS stations located in Tashkent, Kitab, and Maidanak in Uzbekistan, and Islamabad, Multan, Quetta in Pakistan. The results show continuous anomalous variations in TEC during 24 h before the occupancy of local earthquakes. It is shown that the precursors before the occurrence of strong earthquakes, in particular of magnitude 5.7, 7.7, 7.5, 7.8 and 7.3 are detected near Eastern Uzbekistan (26 May 2013), Southwestern Pakistan (24 September 2013), Hindukush region of Afghanistan (26 October 2015), and Central Nepal (25 April 2015) and (12 May 2015), respectively. The ionospheric anomalies appearing before the strong earthquakes at six GNSS stations are registered in 14 cases (70%) out of 20 selected EQs. It is depicted that anomalies referred to as ionospheric precursors appeared about 1–7 days prior to the occurrence of strong earthquakes.

New Parameter for Analysis of Ionospheric Disturbances and the Search for Ionospheric Precursors of Earthquakes Based on Barbier’s Formula

A new relative parameter (δBarbier) is proposed for the analysis of ionospheric disturbances and the search for ionospheric precursors of earthquakes. The parameter is derived on the basis of the semiempirical Barbier’s formula, in which directly and simultaneously measured ionospheric parameters are used: the critical frequency of F2 layer of the ionosphere foF2 and the virtual minimum height of F region h'F. The time prior to a 6.2-magnitude earthquake that occurred in the vicinity of the ground-based station of vertical ionospheric sounding MAUI (Hawaii) on June 26, 1989, is considered as an example of the use of this parameter and its interpretation. We show that δBarbier ≤ 0 during dark hours, from 2000 to 0400 local time, against the geomagnetically quiet background (Kp ≤ 2+) on June 25, 1989, i.e., the day before the earthquake. This behavior is interpreted as a decrease (as compared to the median) in the glow intensity of the atomic oxygen O(1D) emission in the red line (630 nm) estimated from ionospheric data, which is associated with the dissociative recombination of {text{O}}_{2}^{ + } ions at altitude of the F region during this time. The studied effect can be seismogenic and can serve an ionospheric precursor of an earthquake.

Detection of Possible Short-Term Ionospheric Precursors of Strong Earthquakes Based on Changes in Diurnal Es Characteristics

The changes in two characteristics of the sporadic Е layer are studied for a pair of stations: the probability of the occurrence PEs and the limiting frequency of the ordinary wave of the sporadic E layer of the ionosphere foEs during a 10-day period of the preparation of 19 crustal earthquakes in the Pacific region with М = 6.5–7.4. The stations are located hundreds of kilometers from each other, but they fall within the zone of the preparation of a particular earthquake (the sizes of the earthquake preparation zone are estimated with formulas known in the scientific literature that relate the size of the radius of the earthquake preparation zone and the earthquake magnitude). The measurement data obtained at the ground stations of ionospheric vertical sounding are analyzed. The deviations of diurnal values of PEs (δPEs) from the median over the studied time interval and the integral diurnal values of the total irregular fluctuations in foEs (ΔfEsΣ) are used to identify possible ionospheric earthquake precursors. The coincidence of the time of appearance of the deviation maxima for both parameters before the earthquakes at each of the stations on the same day (from 1 to 4 days before the earthquake day) is recorded in the diurnal changes in the indicated values during the preparation periods of all of the considered earthquakes. The criteria for the identification of a short-term ionospheric earthquake precursor is discussed. Comparison of the analysis results for manual and automatic ionogram processing showed the prospects for the use the proposed parameters obtained according to the data of the distant ionosondes to identify the short-term ionospheric precursors of an earthquake with М = 6.5–7.0.

The capabilities of analyzing the seismo-electromagnetic satellite CSES-01 data for monitoring of seismic activity of the Northern Tien Shan

The relationship between space weather and earthquakes occurring in seismically active areas with the seismo-electromagnetic satellite CSES-01 data are observed. The study assumes the presence of possible ionospheric precursors of strong earthquakes. The sets of measuring instruments of the satellite and data are considered. Subsequently, to prove the non-random nature of the space weather effects, the results of ground-based geomagnetic or electromagnetic observations should be used, for example, magnetotelluric soundings (MTS). Stationary and regime points of the MTS network of the Research Station RAS in Bishkek (RS RAS) are suitable for these purposes in the Northern Tien Shan. The MTS data are presented in the form of hourly frequency-time series with system rotation from 0° to 180°. To obtain information on earthquakes, it is proposed to use data from the NEIC or ISC seismic catalog, since they aggregate data from regional catalogs, including the KNET seismological network maintained by the RS RAS. It is concluded that it is necessary to select the CSES-01 trajectories and times of flight over the territory of Kyrgyzstan and download the electric field detector (EFD) data. The results of comparing satellite and ground-based observations can be used in future technologies for short-term earthquake prediction.

Reduction of the VLF Signal Phase Noise Before Earthquakes

In this paper we analyse temporal variations of the phase of a very low frequency (VLF) signal, used for the lower ionosphere monitoring, in periods around four earthquakes (EQs) with magnitude greater than 4. We provide two analyses in time and frequency domains. First, we analyse time evolution of the phase noise. And second, we examine variations of the frequency spectrum using Fast Fourier Transform (FFT) in order to detect hydrodynamic wave excitations and attenuations. This study follows a previous investigation which indicated the noise amplitude reduction, and excitations and attenuations of the hydrodynamic waves less than one hour before the considered EQ events as a new potential ionospheric precursors of earthquakes. We analyse the phase of the ICV VLF transmitter signal emitted in Italy recorded in Serbia in time periods around four earthquakes occurred on 3, 4 and 9 November 2010 which are the most intensive earthquakes analysed in the previous study. The obtained results indicate very similar changes in the noise of phase and amplitude, and show an agreement in recorded acoustic wave excitations. However, properties in the obtained wave attenuation characteristics are different for these two signal parameters.

Method for Cognitive Identification of Ionospheric Precursors of Earthquakes

A significant proportion of publications related to the ionospheric disturbances that arise during earthquake preparation over the regions of their preparation refer to these disturbances as anomalies. In this case, the identification of the ionospheric precursor is actually based on an estimate of the amplitude of the deviation of the ionospheric parameters from the undisturbed value. We propose a completely different approach based on the physical mechanism of the generation of disturbances created by the interaction of the ionosphere with the lithosphere and atmosphere. At the same time, this interaction gives the observed variations unique properties that are typical only for earthquake precursors, based on which the precursors are identified with an intelligent algorithm. Another advantage of this approach is that the method, which we call “cognitive identification”, does not require large deviations from unperturbed values, since it is based on recognition of the “image” of the precursor. It is created in a way that considers morphological features of the precursors and can be effectively used even at low values of the signal/noise ratio.

Estimation of the Ionospheric Effects of Geomagnetic Disturbances Based on Data from Wakkanai Station

Ionosonde measurements of the critical frequency of the ionospheric F2 layer (foF2) at Wakkanai station (Japan) are analyzed with the method of superposed epochs. The station is situated in a region of high seismicity. Winter periods with low sunspot and geomagnetic activity and high seismic activity are considered. The goals of this work were the quantitative characterization and comparison of ionospheric disturbances induced by the development of geomagnetic storms/geomagnetic disturbances. Geomagnetic disturbances refer to manifestations of geomagnetic activity with an intensity that is higher than “quiet” geomagnetic background but not higher than the threshold characteristic of weak geomagnetic storms. It is ascertained that weak geomagnetic storms and geomagnetic disturbances, from the time of the main trough in the Dst index after the onset of a geomagnetic storm/geomagnetic disturbance to the end of the third day, result in only positive foF2 deviations. The deviations exceed 6% of the background; the maximal relative deviations from the background (δfoF2max) are ~17% and ~14%, respectively. For geomagnetic disturbances, the most significant response of the ionosphere is observed ~7 h after the main trough in the Dst index. The resulting assessments can be used to filter out false ionospheric earthquake precursors with analysis of the ionospheric data from Wakkanai station.

Investigation of Ionospheric Earthquake Precursors Using US-TEC Data during the Solar Maximum of 2013–2015

Recent studies have suggested that detectable ionospheric disturbances precede earthquakes. In the present study, variations in the vertical total electron content (TEC) for eight earthquakes with magnitudes of M ≥ 5.5 in the western United States were investigated during the solar maximum of 2013–2015 using United States total electron content (US-TEC) data provided by the National Oceanic and Atmospheric Administration. Analyses of 12 earthquakes with magnitudes of 5.0 ≤ M < 5.5 in the same region were also performed. The TEC variations were examined for 40 days, including the times when the earthquakes occurred. The results indicated a correlation between earthquakes with magnitudes of M ≥ 5.0 and ionospheric TEC anomalies. TEC anomalies occurred before 60% of the earthquakes. Additionally, they were more frequently observed for large earthquakes (75%, M ≥ 5.5) than for small earthquakes (50%, 5.5 > M ≥ 5.0). Anomalous increases in the TEC occurred 2–18 days before the earthquakes as an ionospheric precursor, whereas solar and geomagnetic activities were low or moderate.

Formation of Ionospheric Precursors of Earthquakes—Probable Mechanism and Its Substantiation

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 and critical comparison of several basic mechanisms of action on the ionosphere from below: the propagation of electromagnetic radiation; the closure of the atmospheric currents through the ionosphere; the penetration of waves throughout the neutral atmosphere. A further part of the article is devoted to the analysis of theoretical and experimental information relating to the actual GWs. Simple analytical expressions are written that allow one to calculate the parameters of GWs in specific experimental situations. Specificity of GW dispersion properties and features of their propagation are analyzed on this mathematical basis, processes of amplitude amplification and dissipation of GWs with height are investigated, the mechanism of generation of ionosphere-magnetosphere current systems is described and their quantitative characteristics are determined. The experimental part presents an analysis of GWs global distribution in the thermosphere derived from the data of the instrument NACS (Neutral Atmosphere Composition Spectrometer) onboard the satellite DE-2 (NASA, 1981-1983). The statistical association of registered ionospheric disturbances with earthquakes is demonstrated. The results of DE-2 data processing are backed up by comparison with data from the DEMETER satellite (CNES, 2005-2010) whose purpose was to study the ionospheric effects of earthquakes. Specific features of GWs that characterize these waves as a factor of influence on the ionosphere from below are indicated.

Precursory worldwide signatures of earthquake occurrences on Swarm satellite data

The study of the preparation phase of large earthquakes is essential to understand the physical processes involved, and potentially useful also to develop a future reliable short-term warning system. Here we analyse electron density and magnetic field data measured by Swarm three-satellite constellation for 4.7 years, to look for possible in-situ ionospheric precursors of large earthquakes to study the interactions between the lithosphere and the above atmosphere and ionosphere, in what is called the Lithosphere-Atmosphere-Ionosphere Coupling (LAIC). We define these anomalies statistically in the whole space-time interval of interest and use a Worldwide Statistical Correlation (WSC) analysis through a superposed epoch approach to study the possible relation with the earthquakes. We find some clear concentrations of electron density and magnetic anomalies from more than two months to some days before the earthquake occurrences. Such anomaly clustering is, in general, statistically significant with respect to homogeneous random simulations, supporting a LAIC during the preparation phase of earthquakes. By investigating different earthquake magnitude ranges, not only do we confirm the well-known Rikitake empirical law between ionospheric anomaly precursor time and earthquake magnitude, but we also give more reliability to the seismic source origin for many of the identified anomalies.

SEISMO-MAGNETIC FIELD ANOMALIES DETECTION USING SWARM SATELLITES (ALPHA, BRAVO AND CHARLIE)

Abstract. Among the lithospheric, atmospheric and ionospheric earthquake precursors, it seems that the ionospheric anomalies showing a meaningful association with seismic activities during absence of solar and geomagnetic activities. Unfortunately there are a limited number of satellite sensors to survey the ionosphere and study on seismo-ionospheric anomalies. This paper represents the data analysis results of Swarm satellites including Alpha, Bravo and Charlie data around the Mexico (September 8, 2017) earthquake. The orbital analysis and time series of magnetic field parameters (magnetic scalar and vectors (X, Y, Z) components) inside the Dobrovolsky’s area show anomalous variations close to the time and locations of the Mexico earthquake. There is a concavity or convexity variations in the some of the time-series to the centre of the earthquake day. In other words, from about 90 days before the event a decreasing or increasing trend in variations of parameters is observed and exactly after the earthquake day its trend changes. It should be noted that the variations of the solar and geomagnetic indices must indicate a normal behaviour during the observed seismo-ionospheric anomalies. Therefore this study indicates that the Swarm satellites measurements play an undeniable role in progress the studies of the ionospheric precursors.

Methods for the Evaluation of the Stochastic Properties of the Ionosphere for Earthquake Prediction—Random Matrix Theory

Seismo-ionospheric coupling is a field of great interest and is currently subject to rigorous study; using both ground and satellite data and many phenomenological features, the ionospheric precursors of earthquakes were identified. In this work, we present methods to study the stochastic properties of the lower ionosphere, derived from the data obtained with very low frequency (VLF) receivers at frequencies in the range of 19.6 to 37.5 kHz. Two main approaches are described: auto-correlation and random matrix theory treatments of amplitude time series data. It is shown that before shallow earthquakes with magnitudes greater than four, there are measurable changes that can be used in earthquake prediction. Although the exact form of the causal chain that leads to these changes are currently subject to diligent study, we believe that the investigations described herein are worth adding to the repertoire of ionospheric precursors.

Computer Analysis of Total Electron Content in the Earth’s Ionosphere in Problems of Searching for and Detection of Earthquake Precursors: Current Problems and Challenges

The article reviews methods for the computer analysis and detection of so-called ionospheric earthquake precursors. It is shown that the applied techniques lead to quantitatively incomparable results due to the differences in determination of a reference undisturbed variation and in quantitative criteria of considering disturbances anomalous. As the existing techniques do not take into account the known sample standard deviation (provided by NASA along with the global ionospheric maps of total electron content for the Earth’s ionosphere), the amplitude of revealed anomalies cannot be compared to the level of natural variability of the ionosphere. To eliminate this shortcoming, we propose a few metrics to determine numerical criteria that enable to classify as anomalous the total electron content disturbances observed before strong earthquakes.

Small-Scale Plasma Irregularities in the Ionospheric D Layer

Taking into account the vertical current in the Earth’s atmosphere and rejecting the frequently used quasineutral plasma approximation, which is wrong in the given case, the existence in the ionospheric D layer of thin plane regions with a characteristic size of ~1 m in which the plasma density increases abruptly with altitude is shown. Especially strong variations in the plasma density occur in the equatorial ionosphere, where the geomagnetic field is horizontal. The magnitude of the plasma density jump strongly depends on the electric field E at the lower boundary of the layer. In particular, at E = 0.1 V/m and an altitude of 85–90 km in the equatorial ionosphere, the plasma density jumps by a factor of 3.6, while at E = 0.2 V/m, by a factor of 15.5. A mechanism for the emergence of ionospheric precursors of earthquakes associated with the presence of such a jump is offered.

Ionospheric anomalies preceding the low-latitude earthquake that occurred on April 16, 2016 in Ecuador

A catastrophic seismic event of Mw 7.8 occurred on April 16, 2016 in Ecuador. As with some other major earthquakes, many human lives were lost. Thus in the last two decades, the search for seismo-ionospheric signatures has become an active field of research. In order to provide further insights into ionospheric precursors of earthquakes, Global Ionospheric Maps (GIMs) provided by the Center for Orbit Determination in Europe (CODE) were used to look for ionospheric anomalies prior to the earthquake in Ecuador. By producing differential Vertical Total Electron Content (VTEC) maps and using a statistical method, a negative ionospheric anomaly was observed 10 days before the incident. At different confidence levels the negative disturbance was permanently visible. This anomaly also is located within the earthquake preparation zone, defined by the Dobrovolsky equation. Additionally, due to the extreme low-latitude nature of the earthquake, the dynamics of the Equatorial Ionization Anomaly (EIA) shape were observed. A further confirmation of the ionospheric anomaly was provided by the dramatic change of the EIA 10 days before the earthquake with respect to a non-disturbed day. Due to the really quiet geomagnetic and solar conditions for April 6, 2016, the negative anomaly is considered to be a seismo-ionospheric signature.