Displays

An order parameter for seismicity was introduced in the frame of natural time analysis [1].  Recent studies of the fluctuations of this order parameter revealed the existence of minima preceding major earthquakes [2-7]. Here, we review the statistical significance of these minima by using recent methods of Statistical Physics, such as receiver operating characteristics [8] and event coincidence analysis [9,10]. These methods are also applied to the investigation [11] of the statistical significance of Seismic Electric Signals [12].

References

1. Varotsos, P.A.; Sarlis, N.V.; Skordas, E.S. Natural Time Analysis: The new view of time. Precursory Seismic Electric Signals, Earthquakes and other Complex Time-Series; Springer-Verlag: Berlin Heidelberg, 2011.
2. Sarlis, N.V.; Skordas, E.S.; Varotsos, P.A.; Nagao, T.; Kamogawa, M.; Tanaka, H.; Uyeda, S. Minimum of the order parameter fluctuations of seismicity before major earthquakes in Japan, Proc. Natl. Acad. Sci. USA 110 (2013) 13734–13738, dx.doi.org/10.1073/pnas.1312740110.
3. Varotsos, P.A.; Sarlis, N.V.; Skordas, E.S. Study of the temporal correlations in the magnitude time series before major earthquakes in Japan. J. Geophys. Res.: Space Physics 119 (2014) 9192–9206, dx.doi.org/10.1002/2014JA020580.
4. Sarlis, N.V.; Christopoulos, S.R.G.; Skordas, E.S. Minima of the fluctuations of the order parameter of global seismicity. Chaos 25 (2015) 063110, dx.doi.org/10.1063/1.4922300.
5. Sarlis, N.V.; Skordas, E.S.; Christopoulos, S.-R.G.; Varotsos, P.A. Statistical significance of minimum of the order parameter fluctuations of seismicity before major earthquakes in Japan, Pure Appl. Geophys. 173 (2016) 165–172, dx.doi.org/10.1007/s00024-014-0930-8.
6. Sarlis, N.V.; Skordas, E.S.; Mintzelas, A.; Papadopoulou, K.A. Micro-scale, mid-scale, and macro-scale in global seismicity identified by empirical mode decomposition and their multifractal characteristics. Scientific Reports 8 (2018) 9206, dx.doi.org/10.1038/s41598-018-27567-y.
7. Mintzelas, A.; Sarlis, N. Minima of the fluctuations of the order parameter of seismicity and earthquake networks based on similar activity patterns. Physica A 527 (2019) 121293, dx.doi.org/10.1016/j.physa.2019.121293.
8. Fawcett, T., An introduction to ROC analysis, Pattern Recognit. Lett. 27 (2006) 861–874, dx.doi.org/10.1016/j.patrec.2005.10.010.
9. Donges, J.; Schleussner, C.F.; Siegmund, J.; Donner, R. Event coincidence analysis for quantifying statistical interrelationships between event time series. The European Physical Journal Special Topics 225 (2016) 471–487, dx.doi.org/10.1140/epjst/e2015-50233-y.
10. Siegmund, J.F.; Siegmund, N.; Donner, R.V. CoinCalc - A new R package for quantifying simultaneities of event series. Computers & Geosciences 98 (2017) 64-72, dx.doi.org/10.1016/j.cageo.2016.10.004.
11. Sarlis, N.V. Statistical Significance of Earth’s Electric and Magnetic Field Variations Preceding Earthquakes in Greece and Japan Revisited. Entropy 20 (2018) 561, dx.doi.org/10.3390/e20080561.
12. Varotsos, P.; Lazaridou, M. Latest aspects of earthquake prediction in Greece based on seismic electric signals, Tectonophysics 188 (1991) 321–347, dx.doi.org/10.1016/0040-1951(91)90462-2.

How to cite: Varotsos, P. A., Sarlis, N. V., Skordas, E. S., and Christopoulos, S.-R. G.: Statistical significance of the precursory minima of the order parameter fluctuations of seismicity by modern methods of Statistical Physics, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7482, https://doi.org/10.5194/egusphere-egu2020-7482, 2020.

In this work we use Very Low Frequency (VLF) radio signals, having a frequency in the bands 20-80 kHz, to study the VLF signal propagation in the atmosphere quite undisturbed conditions by selecting the signals recorded during night. As a good approximation, we can model the propagation of VLF radio signals as characterized by a ground-wave and a sky-wave propagation mode. The first one generates a radio signal that propagates in the channel ground-troposphere, while the second one generates a signal which propagates using the lower ionosphere as a reflector. The VLF receivers of the INFREP (European Network of Electromagnetic Radiation) network are used. These receivers have been installed since 2009 mainly in southern and central Europe and currently the INFREP network consists of 9 receivers. A 1-minute sampling interval is used to record the amplitude of VLF signals. Long time-series of VLF signals propagating during night are extracted from recorded signals to study possible seasonal effects due to temporal variations in the physical properties of troposphere. A graph theory approach is used to investigate the spatial correlation of the aforementioned effects at different receivers. A multivariate analysis is also applied to identify common temporal changes observed at VLF receivers.

This work was supported by the Ministero dell'Istruzione, dell'Università e della Ricerca (MIUR), Italy, under the project OT4CLIMA. This research is supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia, under the projects 176002 and III44002.

How to cite: Nico, G., Nina, A., Ermini, A., and Biagi, P.: On the characterization of VLF radio signal propagation in atmosphere in quite solar conditions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9197, https://doi.org/10.5194/egusphere-egu2020-9197, 2020.

Influenced by the extrusion of Tibetan blocks and Indo-Burmese collision, the region in western Yunnan is associated with active seismicity and Quaternary volcanoes. Based on broadband magnetotelluric data collected in western Yunnan, we obtain a three-dimensional crustal electrical resistivity model after various data processing and three-dimensional inversion test. The above resistivity model reveals the seismogenic structures of the moderate and strong earthquakes in this tectonic region. We investigate the possible relationship between the seismicity and the electrical structure in western Yunnan region. The results indicate that earthquakes in this region tend to occur in the transition zone between the resistive and conductive structures. Our results also show that one resistive body imaged at the mid-lower crust may have blocked the previously proposed crustal channel flow along this intra-continental block boundary to the east of Tibetan Plateau. Our resistivity model suggests a bifurcation of the crustal flow in western Yunnan. This bifurcated crustal flow structure may play an important dynamical role in the seismogenesis of the earthquakes in western Yunnan.

How to cite: Huang, Q., Ye, T., and Chen, X.: Seismogenic structures in western Yunnan revealed by three-dimensional magnetotelluric imaging, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9259, https://doi.org/10.5194/egusphere-egu2020-9259, 2020.

Since 2009, the stress-strain state of the earth’s crust in South California region is being tracked utilizing the geomechanical model accounting for all the current seismicity. Every new earthquake is treated as a new defect in the Earth's crust, causing the stress-strain state redistribution. Through the continuous stress-strain state update, we found that all the significant earthquakes in the area, including those with M ~ 7 in 2010 and 2019, had been preceded by the anomalies in the strength parameter

How to cite: Gokhberg, M., Bondur, V., Garagash, I., and Alekseev, D.: Short-term precursors of the M=5.5-7.2 earthquakes in South California revealed from the simulated stress-strain state patterns, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13120, https://doi.org/10.5194/egusphere-egu2020-13120, 2020.

A catastrophic earthquake of magnitude Mw6.4 generated at 10km depth hit coastal zone of Albania on November 26-th 2019, at 2h54min UTC. The earthquake was intensively felt at about 34km far, in Tirana City, where a lot of damages have occurred. Consequently, in order to identify the anomalous geomagnetic signature before the onset of this earthquake, we retrospectively analyzed the data collected on the interval October 15–November 30, 2019 at the two geomagnetic observatories: Panagjurishte (PAG)-Bulgaria and Surlari (SUA)-Romania, the last one taken as reference. The pre-seismic geomagnetic anomalous signal is postulated to be due to the electrical conductivity changes, most probably associated with the earthquake-induced tectonic stress, followed by rupture and electrochemical processes deployed along the Adria plate subduction zone. To identify a pre-seismic geomagnetic signal related to this earthquake we used: (i) polarization parameter BPOL which should be time invariant in non-seismic condition and it becomes unstable before the onset a seismic event; (ii) Strain effect-related to the anomalous geomagnetic signals identification. Thus, the daily mean distributions of the BPOL and its standard deviations (SD) are performed for the both observation site (PAG and SUA) by using the FFT band-pass filter analysis in the ULF range (0.001Hz - 0.0083Hz). Further on, a statistical analysis based on a standardized random variable equation was applied for the two particular cases: a) the assessment of the singularity for anomalous signal, related to the Mw6.4earthquake, observed on the daily mean distributions of the BPOL*(PAG) and BPOL*(SUA); b) the differentiation of the transient local anomalies associated with Mw6.4earthquake from the internal and external parts of the geomagnetic field, taking Geomagnetic Observatory (SUA) as reference, and the result is presented as daily mean distribution of the BPOL*(PAG-SUA). Finally, on the BPOL*(PAG-SUA) time series, carried out on the interval 1-30 November 2019, a very clear anomaly of maximum greater than 2.5 SD was detected on November 22, what means a lead time of 4 days before the onset of Mw6.4earthquake. In consequence, all mentioned results could offer opportunities to develop new tools for early detection of geomagnetic anomalies related to major seismic events. 

How to cite: Stanica, D. and Stanica, D. A.: Possible correlation beteen the pre-seismic geomagnetic signal and the M6.4 earthquake generated in the coastal zone of Albania, on November 26, 2019 , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13795, https://doi.org/10.5194/egusphere-egu2020-13795, 2020.

A novel forecasting tool, able to fully exploit the information content of the available data, is proposed for the synergic use of seismological and geodetic information, in order to delineate, at the intermediate-term narrow-range, the regions where to concentrate prevention actions and seismic risk mitigation planning. An application of the proposed interdisciplinary procedure, defining a new paradigm for time dependent hazard assessment scenarios, is exemplified illustrating its application to the Italian territory.

From seismological viewpoint, long-lasting practice and results obtained for the Italian territory in two decades of rigorous prospective testing of fully formalized algorithms (e.g. CN), proved the feasibility of earthquake forecasting based on the analysis of seismicity patterns at the intermediate-term (i.e. several months) middle-range scale (i.e. few hundred kilometers). An improved but not ultimate precision can be achieved reducing as much as possible the space-time volume of the alarms, by jointly considering seismological and geodetic information. In the proposed scheme geodetic information (i.e. GNSS and SAR) are used to reconstruct the velocity and strain pattern along transects properly oriented according to the a priori known tectonic and seismological information. Specifically, considering properly defined transects within the regions monitored by CN algorithm, the possible velocity variations and the related strain accumulation can be highlighted, with due consideration of the errors involved in GNSS data.

Through a refined retrospective analysis, duly involving the accuracy analysis of the newly available geodetic results, space­time precursory features could be highlighted within ground velocities and seismicity, analyzing the 2016-2017 seismic crisis in Central Italy and the 2012 Emilia sequence. The analysis, including counter examples, evidenced reliable anomalies in the strain rate distribution in space, whereas no time dependence was detected in the long term (more than 10 years) preceding the occurrence of the studied events.

With these results acquired, a systematic analysis of velocity variations (together with their accuracy) is performed, by defining a set of transects uniformly distributed, as far as possible, along and across major seismotectonic features of the Italian region, with a spacing of about 40-50 km and properly covering the regions monitored by CN algorithm. As a rule most of the transects contain information that appear to be useful for earthquake forecasting purposes. The few exceptions, naturally connected with the local very limited extension of land, are in Calabria and Western Sicily.

The obtained results show that the combined analysis of the results (time dependent within decadal interval) of intermediate-term middle-range earthquake prediction algorithms, like CN, with those from the processing of adequately dense and permanent GNSS network data (time independent within the same decadal interval), may allow to highlight in advance the localized strain accumulation. Accordingly the extent of the alarmed areas, identified based on seismicity patterns at the intermediate scale can be significantly reduced (from few hundred to few tens kilometres).

How to cite: Peresan, A., Crespi, M., Riguzzi, F., Kossobokov, V., and Panza, G. F.: Intermediate-term narrow-range earthquake forecasting: an interdisciplinary tool based on seismological and geodetic observations, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18302, https://doi.org/10.5194/egusphere-egu2020-18302, 2020.

If A and B are physical events at t=t₁ and t=t₂, respectively, in the same differential topological domain where t₁<t₂ then A and B may attract each other through bidirectional communication-like information even if A and B are not in the same physical cathegory. This fact comes from the similarity effect of physical events those obey always to a 2nd order partial differential equation, PDE at specific boundary conditions, SBCs. The coefficients in the operator part and the source function part of the PDE and propagation factors of the eigenfunctions in the solution and SBCs differ from an event cathegory to other event cathegory; however stochastic interpretations of these coefficients, source functions, eigenfunctions, and SBCs bring a unique and compact boundary value problem, BVP. We call network BVP this type of extended BVPs. The common parts of different types of events A and B in the same BVP scheme are topology and boundary surfaces of the same domain. The relationship between event A and event B is based on inversely transferring of boundary values, source functions, and coefficients between each other of the events through topological transformations, TTs. These TTs establish the bidirectional information communication between both climatic and seismic processes. All the natural events and hazards involving disasters are the self-control mechanism of the Completely Compact Earth Network, CCEN. The sea is a way and transfer medium for waves by Pascal’s rule.

The constrainers of Present Natural Hazards, PrNHs, are the Future Natural Hazards, FuNHs. The Past and/or Backward NHs (PaNHs, BwNHs) completed their results and could not effect to the PrNHs.

The results obtained with the methods of classical geophysics built on the classical Newton’s mechanics does not reflect the real processes, RPs for the magnitudes more than 5.9 Richter. The approaches built on Einstein’s relativity can not generate RPs for the interwall of over 6.9 Richter; i.e., a temporal transportation occurs in the last domain: Kocaeli-Mediterranean Sea EQ in 1999 is a result of both backward majorant propagation effect, BMaPE of Hector Mine EQ occured after itself and forward majorant propagation effect, FoMaPE of the seismicity to Future İstanbul Earthquake, sFIEQ. This means the raising period of FIEQ is released.The constrainer of 1999 Taiwan EQ is a result of BMaPE of Duzce EQ occured after itself. The constrainers of 2019 Silivri, Albania, and Athens EQs are the FIEQ desired in demand for future but never come. 1999 Avcilar EQ is a result of backward minorized propagation effect, BMiPE of the sFIEQ. This means the waiting/relaxation period of FIEQ is suspended. These  are figured from the specific records of these events observed during 1999-2004 and 2018-2020. The couplings among ionospheric, atmospheric, oceanographic, climatic, and/or seismic processes provide the communication among the events of different cathegories in here. We define this principle as the spati-o-temporal transplantation effect in EQ processes.

The SIDT is the most safe region on the Earth for the majorant earthquakes and preserves this property iff unconvenient/unnatural buildings and major excavations are excluded from this topology.

How to cite: Sengor, T.: The Coupling-Transplantation Effect (CTE) and Differential Analytical-Physics-Topology Principle (DAPTP) in Ionospheric-Atmospheric-Oceonagraphic-Climatic-Seismic Processes Complex (IAOCSPC) with Observations in Specific Istanbul Domain Topology (SIDT), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22589, https://doi.org/10.5194/egusphere-egu2020-22589, 2020.

Many examples of ionospheric perturbations observed in large seismic events were recorded by the low-altitude satellite DEMETER. In this paper, we explore 16 spot-checking classification algorithms, among which, the top classifier with low-frequency power spectra of electric and magnetic fields were used for ionospheric perturbation analysis. Satellite data spanning over about 6 years has been analyzed and about 8,760 earthquakes with magnitudes larger than or equal to 5.0 that occurred all over the world during the analyzed period have been included in the study. We discover that among these methods, gradient boosting based method called LightGBM outperforms the other state-of-the-art methods and achieves AUC (the Area Under the Curve) of 0.9859 and accuracy of 95.01% in a five-fold cross-validation test on the benchmarking datasets. In addition, the LightGBM method shows a strong capability in discriminating electromagnetic pre-earthquake perturbations over different earthquake databases. The results show that electromagnetic pre-earthquake data with the location in its circular region with its center at the epicenter and a radius given by the Dobrovolsky’s formula and the time of a few hours before the shocks is more useful in discriminating electromagnetic pre-earthquake perturbations. Moreover, we observe that during nights, some low-frequency intervals of electric and magnetic fields are the dominant features as rendered by the trained LightGBM model. These observations support the viewpoint that the seismic activities lead to the enhancement of lightning activity and low frequency electromagnetic pre-earthquake data can help us to detect seismic events.

How to cite: Xiong, P., Long, C., Zhou, H., Battiston, R., Zhang, X., and Shen, X.: Identification of electromagnetic pre-earthquake perturbations from the DEMETER data by AI technologies, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2506, https://doi.org/10.5194/egusphere-egu2020-2506, 2020.

We present a multi parameters analysis of satellite and ground data that revealed a transient phenomenon in the atmosphere before the M6.4 earthquake in Albania on Nov 26, 2019. The observational methodology consists of data from five physical measurements: (1) Satellite Thermal Anomalies (data obtained from NOAA) on the top of the atmosphere; (2); Atmospheric chemical potential (ACP) obtained from the NASA assimilation models; (3); Measurement of Radon level variations (two gamma stations in Central Italy); (4) VHF propagation in the lower atmosphere from ground observations and; (5) Electron density variations in the ionosphere via GPS Total Electron Content (GPS/TEC)

On Nov 21, 2019 our NOAA STA daily analysis over the Mediterranean detected a strong abnormal pattern between Italy and Albania. We estimated that a possible earthquake could occur in the Adriatic Sea between Italy and Albania with M5.5+ and start cross parameter validation with other observations. On Nov 26 an earthquake occurred near STA anomaly of Nov 21. The epicenter of the M6.4 earthquake in Albania is situated about 500 kilometers NE of the two-radon monitoring stations in Central Italy. Real-time hourly data show an increase in both sensors on Nov 20 (6 days before the M6.4 of Nov 26, 2019). From the satellite data these increases in radon coincide with an increase in the atmospheric chemical potential (on Nov 21), measured near the epicentral area. VHF data observed from two stations located 300 km from the epicenter in Northeast Bulgaria, indicated an intensity modulation about 90 hours (3.5 days) before the mainshock. The GPS/Total Electron Content data indicated an increase of electron concentration in the ionosphere 1-2 days before the M6.4 earthquake. We observed a synergetic abnormal response from ground and satellite data, although the ground data (radon and VHF) sensors were far from the epicenter (500 and 300 km, respectively). Starting six days before the M6.4 Nov 26 earthquake, the anomalous patterns were inside the Dobrovolsky-Bowman area of preparation. We examined the possible correlation between different pre-earthquake anomalies and the relationship between magnitude and the spatial size of the preparation zone in the framework of the Lithosphere -Atmosphere -Ionosphere Coupling (LAIC) concept.

How to cite: Ouzounov, D., Pulinets, S., Guiliani, G., Velichkova-Iotsova, S., Kafatos, M., and Taylor, P.: Pre-earthquake processes associated with the M6.4 of Nov 26, 2017 In Albania. A Multi parameters analysis., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6251, https://doi.org/10.5194/egusphere-egu2020-6251, 2020.

In the last few decades several parameters (chemical, physical, biological, etc.) have been proposed in association with the complex process of preparation of earthquakes. In particular, the variability of space weather has been proposed, since long time, as possible indicator of impending earthquakes. This variability can be optimally captured by the detection of anomalous Ionospheric-Total Electron Content (TEC) variations.

The investigation of the preparation phase of past strong earthquakes could be useful to understand the physical processes involved and to develop a future short-term warning system.

Since 2001, the general change detection approach RST (Robust Satellite Techniques; Tramutoli, 1998; 2005; 2007) has been used to discriminate anomalies in Earth’s thermal emission measured by satellite possibly associated to seismic activity, from normal fluctuations of the signal related to other causes (e.g. meteorological) independent on the earthquake occurrence.

In this work are shown the results about the use of a RST-based approach for the preseismic TEC anomalies identification.

The RST methodology has been reformulated and adapted in order to be applied to TEC measurements recorded by the GPS satellite constellation, so as to discriminate anomalous signals from normal fluctuations of the signal itself. To this aim, we studied the behavior of the TEC parameter, proceeding to the construction of a multi-year dataset of observations (>5 years) in Mediterranean seismically active areas, both in presence and in absence, of strong seismic events (M≥5).

The achieved results are discussed and compared with the results obtained through independent RST analyses carried out on the Earth’s Thermal Infrared Radiation (TIR) parameter. The comparison of the results obtained using the two parameters is made in order to evaluate how the joint use of both parameters (TEC and TIR) in the framework of a multi-parametric approach can improve the present capability of detection of these perturbations.

How to cite: Colonna, R., Tramutoli, V., Filizzola, C., Genzano, N., Lisi, M., and Pergola, N.: Statistical analysis for the identification of precursory signatures of earthquake occurrence in Total Electron Content (TEC), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9800, https://doi.org/10.5194/egusphere-egu2020-9800, 2020.

Applying a multi-parametric approach, we already investigated the preparatory phase of several medium and large (M6.0 ~ M8.3) earthquakes occurred in the last 6 years in different locations in the World. In some cases, a chain of processes from the lithosphere to atmosphere and ionosphere has been successfully detected (e.g. M7.8 Ecuador 2016: Akhoondzadeh, 2018, ASR, https://doi.org/10.1016/j.asr.2017.07.014; Italian seismic sequence (M6.5) 2016-2017: Marchetti et al., 2019, RSoE, https://doi.org/10.1016/j.rse.2019.04.033; M7.5 Indonesia 2018: Marchetti et al., 2019, JAES, https://doi.org/10.1016/j.jseaes.2019.104097). These analyses underline the importance to study all the “spheres” that surround the Earth as suggested by a Geosystemic approach (De Santis et al., 2019, Entropy, https://doi.org/10.3390/e21040412). To analyse the anomalies that occur in the atmosphere we typically calculate the mean and standard deviation of the “historical time series” of the investigated parameter based on around 40 years of data, and then we superpose the value of the same quantity in the earthquake year. If the value overpasses two standard deviations of the historical time series, we define this day/parameter as anomalous. Applying the same methodology presented in previous works that studied climatological parameters such as skin temperature, total column water vapour, aerosols, and SO₂, which  seem to provide anomalies possibly related to the earthquake preparation phase (e.g. Piscini et al., 2017, PAGeoph, https://doi.org/10.1007/s00024-017-1597-8), here we investigate more atmospheric parameters proposed as possible precursors in the Lithosphere Atmosphere Ionosphere Coupling (LAIC) models (Pulinets and Ouzounov, 2011, JAES, https://doi.org/10.1016/j.jseaes.2010.03.005) such as methane and surface concentration of carbon monoxide. Other parameters, such as dimethylsulfide could be useful in other geophysical events, such as the volcano eruptions (Piscini et al. PAGeoph 2019, https://doi.org/10.1007/s00024-019-02147-x).

In this study, we also apply a Worldwide Statistical Correlation (WSC), as it was successfully applied to Swarm satellites electromagnetic anomalies and earthquakes, providing some statistical evidence for such perturbations in ionosphere before the occurrence of M5.5+ earthquakes (De Santis et al., 2019, Sci. Rep., https://doi.org/10.1038/s41598-019-56599-1).

The statistical approaches applied to these climatological data, provided by meteorological agencies such as ECMWF and NOAA, provides some interesting concentrations of atmospheric anomalies, preceding from days to several weeks the occurrence of the largest earthquakes from 1980 to 2017.

The study of several chemical and physical (e.g. aerosol particles) components in the atmosphere, the involved physical processes, the chemical reactions and chemical constraints (such as the elements lifetime and interactions in the atmosphere) can help to distinguish which LAIC model is more reliable to produce the observed anomalies before the occurrence of a large earthquake.

How to cite: Marchetti, D., Piscini, A., De Santis, A., Ganglo, C., Cianchini, G., A. Campuzano, S., Cesaroni, C., Haagmans, R., Jin, S., Spogli, L., Soldani, M., and Ippolito, A.: Systematic worldwide statistical correlation of physical and chemical atmospheric parameters before large earthquakes in the last four decades, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19809, https://doi.org/10.5194/egusphere-egu2020-19809, 2020.

Rikitake [1987] studied different types of ground earthquake precursors and presented an empirical law (for what he called “precursors of the 1st kind”) expressing a linear relationship between the logarithm of the anomaly precursor time and the earthquake magnitude. To look for possible in-situ ionospheric precursors of large (M5.5+) earthquakes, here we analyse a long-term time series data from the three-satellite Swarm constellation, in particular electron density and magnetic field data. We define the anomalies statistically in the whole space-time interval of interest and use a superposed epoch approach to study the possible relation with the earthquakes. We find some clear concentrations of electron density and magnetic anomalies from several months to a few days before the earthquake occurrences. Such anomaly clustering is, in general, statistically significant with respect to homogeneous random simulations, supporting a coupling of the lithosphere with the above atmosphere and ionosphere during the preparation phase of earthquakes. Finally, by investigating different earthquake magnitude ranges, we confirm the Rikitake empirical law between ionospheric anomaly precursor time and earthquake magnitude. Our work represents the first time that this empirical law has been confirmed for satellite data. We also explain this empirical law with a diffusion model of lithospheric stress.

How to cite: Campuzano, S. A., Cianchini, G., De Santis, A., Marchetti, D., Perrone, L., Piscini, A., and Sabbagh, D.: Rikitake Law, relating precursor time and earthquake magnitude, confirmed by Swarm satellite data, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20281, https://doi.org/10.5194/egusphere-egu2020-20281, 2020.

FORMOSAT-7/COSMIC-2 (F7/C2), with the mission orbit of 550 km altitude, 24-deg inclination, and a period of 97 minutes, was launched on 25 June 2019.  Tri-GNSS Radio occultation System (TGRS), Ion Velocity Meter (IVM), and RF beacon onboard F7/C2 six small satellites allow scientists to observe the plasma structure and dynamics in the mid-latitude, low-latitude, and equatorial ionosphere in detail.  F7/C2 TGRS sounds ionospheric RO (radio occultation) electron density profiles, while F7/C2 IVM probes the ion density, ion temperature, and ion velocity at the satellite altitude.  The F7/C2 electron density profiles and the ion density, ion temperature, and ion velocity, as well as the global ionospheric map (GIM) of the total electron content (TEC) derived from global ground-based GPS receivers are used to detect seismo-ionospheric precursors (SIPs) of the 14 November 2019 M7.1 Indonesia Earthquake.  The GIM TEC and F7/C2 RO NmF2 significantly increase specifically over the epicenter on 25-26 October, which indicates SIPs of the 14 November 2019 M7.1 Indonesia Earthquake being detected.  The F7/C2 RO electron density profiles upward motions suggest that the eastward electric fields have been enhanced during the SIP days of the 2019 M7.1 Indonesia earthquake.  The seismo-generated electric fields of the 2019 M7.1 Indonesia earthquake are 0.34-0.64 mV/m eastward.  The results demonstrate that F7/C2 can be employed to detect SIPs in the ionospheric plasma, which shall shed some light on earthquake prediction/forecast.

How to cite: Liu, J.-Y., Lin, C.-Y., Chang, F.-Y., and Chen, Y.-I.: Seismo-ionospheric precursors of the 14 November 2019 M7.1 Indonesia Earthquake detected by FORMOSAT-7/COSMIC-2, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21487, https://doi.org/10.5194/egusphere-egu2020-21487, 2020.

The Earth itself with its inwards and outwards is a unique and complete system according to all events effecting the Earth¹. All the natural events involving hazards are the results of self-controlling mechanism of the complex network of this unique system. Several contributions and reports presented this fact. The classical approaches trying to explain earthquake events, say EQs, and related phenomena may be taken as approximations working for the EQs less than 5.9 Richter in magnitude according to observations coming from the application of this approach. The EQs bigger than 5.9 Richter involve very different ingredients given with dynamics based on the gravity in classical geophysics¹. The ranges of (5.9+n, 5.9+n+1) for every n=1, 2, 3, ... present different formulations due to validity of the approximations and orders of the variables as relative to the energy density and frequency levels.  The fact in here comes with the compactness coming with the electromagnetically equivalent models¹.

The planetary movements effect both the mechanics and dynamics of tectonic plates like tidal action of Pascal’s law modified with stochastic interactions. The Earth’s plates may move and collide with each other due to the forces generated by these displacements. The Primary wave comes from these mechanics of plates under planetary effects, tidal effects, and/or effects of extended Pascal’s and Archimedes’ principles for compressible liquids involving non-adiabatic gasses in semi-open containers. All these effects are effective in vertical direction, totally. P wave is a result of these forces generated by the dynamics of collision of plate-to-plate, plate-to-sea, plate-to-ocean, and/or plate-to-tidal processes coming from planetary motions and acts between plates. Secondary wave come from the effects of Casimir-Polder forces and Van der Waals potentials generated by the nano-displacements occurring among touch-to-touch phases of plates just at the end of P wave phases. These QED effects are effective in horizontal direction in total iff they can generate an EQ. If the plates touch to each other with the effect of forces coming from P wave then this induces Van der Waals potentials and forces like Casimir-Polder force work on the plates generating big amount of energy then big EQs can come to truth. It is possible to model the P wave phases with the deterministic ingredients and processes; however, modelling the S wave phases are not possible without stochastic ingredients and processes. The processes like storms, typhoon, etc. developing with the atmospheric events generate the similar effects. The waves coming with EQs propagate in inflective trajectories; therefore, these waves propagate in inflective spaces. This analysis illustrates the gravity interactions of the Earth with other planets generating electromagnetic interactions in both nano-scale and quantum level in Earth’s interior as the actual trigger of EQs. The excessive fall works like the insurance for EQs preventing the occurrence of significant EQs and so, reducing the huge damage arriving from significant and/or bigger EQs.

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¹Sengor T, “The Globally Compact Multi-Network of the Earth: the self-controlling mechanisms in natural hazards above significant level,” Geophysical Research Abstracts, Vol. 21, EGU2019-17127,2019, General Assembly 2019.

How to cite: Sengor, T.: The Conditional Contributions of Electromagnetism and QED To Natural Hazards in Both Nano and Macro Cosmic Scales, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21121, https://doi.org/10.5194/egusphere-egu2020-21121, 2020.

Natural disasters, such as earthquakes, tsunamis, volcanic eruptions, tropical cyclones (typhoons in the Pacific, hurricanes in America), often lead to enormous human casualties, causing great damage to the human environment. This is due to the unpredictable nature of disasters. Investigation of the precursor signs of the development of such dangerous events (including an assessment of their power) allows you to inform the relevant services in advance of a natural disaster. This is often a very urgent task. The experimental and theoretical study of the electromagnetic response of the ionosphere to the development of natural catastrophic events is an important component of furthering disaster preparedness. This includes improvement of methods for event precursor isolation for use in warning and development systems. In this, validation of lithosphere-ionosphere communication models are very important. Therefore, in this work, we consider the amplitude anomalies of VLF signals recorded at a station in Moscow (Russia) during the passage of an atmospheric/ionospheric seismic wave from an earthquake in Chile, which epicenter is removed at a distance of ~ 15 thousand km.

The work is performed according to the Russian Government Program of Competitive Growth of Kazan Federal University.

How to cite: Yusupov, K., Alexander, R., Maria, S., Sergey, S., Viktor, F., John, M., Ruslan, S., Anvar, S., and Takashi, M.: The response of VLF signals to the passage of an atmospheric/ionospheric seismic wave after an earthquake in Chile, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1240, https://doi.org/10.5194/egusphere-egu2020-1240, 2020.

In this paper, we investigate the ionospheric turbulence from TEC observations, before and during the intense seismic activity of September 2019 at Albania (main shock at l=19.445^oE, j=41.372^o N, M_w=5.6)  and at Marmara sea (main shock at l=28.19 ^oE, j=40.872^oN, M_w=5.7), as well as of November 2019 at Albania (main shock at l=19.470^oE, j=41.381^oN, M_w=6.4), and at Bosnia-Herzegovina (main shock at l=17.961^oE, j=43.196^oN, M_w=5.4).

The Total Electron Content (TEC) data of 6 Global Positioning System (GPS) stations of the EUREF network, which are being provided by IONOLAB (Turkey), were analysed using Discrete Fourier Analysis in order to investigate the TEC variations. The results of this investigation indicate that the High- Frequency limit f_o, of the ionospheric turbulence content, increases by aproaching the site and  the time of the earthquake occurrence, pointing to the earthquake location (epicenter). We conclude that the LAIC mechanism, through acoustic or gravity wave, could explain this phenomenology. In addition the proximity of the tectonic active areas to the GPS stations offer us an opportunity to discriminate the origin of the disturbances

How to cite: Contadakis, M. E., Arabelos, D., Vergos, G., and Scordilis, E. M.: Lower Ionospheric turbulence variations during the intense seismic activity of the last half of 2019 in the broader Balkan region., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1444, https://doi.org/10.5194/egusphere-egu2020-1444, 2020.

In this paper we investigate the ionospheric turbulence from TEC observations before and during the tectonic activity of the last quarter of 2019 in the Hellenic Arc, Greece (main shock at l=23.26^oE, j=35.69^oN, M_w=6.1). The Total Electron Content (TEC) data of 6 Global Positioning System (GPS) stations of the EUREF network, which are being provided by IONOLAB (Turkey), were analysed using Discrete Fourier Analysis in order to investigate the TEC variations. The results of this investigation indicate that the High- Frequency limit f_o, of the ionospheric turbulence content, increases by aproaching the site and the time of the earthquake occurrence, pointing to the earthquake location (epicenter). We conclude that the LAIC mechanism through acoustic or gravity wave could explain this phenomenology.

How to cite: Arabelos, D. N., Contadakis, M. E., Vergos, G., and Scordilis, E. M.: Lower Ionospheric turbulence variations during the tectonic activity of the last quarter of 2019 in the Hellenic Arc (Greece) , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1527, https://doi.org/10.5194/egusphere-egu2020-1527, 2020.

Studies of variations in the intensity of thermal (epithermal) neutrons at the high-mountain station of cosmic rays near the fracture of the earth's crust (3340 m above sea level, Northern Tien- Shan) showed the promising of using them for the diagnosis and forecast of earthquakes in seismically active regions. A method is proposed for distinguishing features of changes in the intensity of thermal neutrons of lithospheric origin against the background of variations caused by solar and atmospheric disturbance sources. However, a necessary condition for this is the synchronous registration of high-energy neutrons of galactic origin.

It is known that neutrons in the Earth’s atmosphere arise mainly as a result of the interaction of primary cosmic radiation with the nuclei of air atoms. Statistical analysis of neutron measurements during effective solar events (coronal mass ejections), changes of atmospheric pressure confirmed the genetic relationship of thermal neutrons near the Earth's surface with high-energy neutrons of galactic origin and the similarity of the spectral composition of their variations. The difference is observed only in the range (2·10^-7÷2·10^-6)Hz. Variations with the period of 29.5 days (synodic lunar month), due to the gravitational influence of the moon, are present throughout the 12-year period of research of thermal neutrons. The amplitude and its changes were determined by the method of complex demodulation. The periodicity of 29.5 days is absent in the spectrum of high-energy neutrons variations.

 Analysis of experimental data during of seismic activity showed the frequent breakdown of the correlation between the intensity of thermal and high-energy neutrons. The cause of this phenomenon is the additional thermal neutron flux of the lithospheric origin, which appears under these conditions. Simple statistical processing of measured parameters makes it possible to exclude variations of interplanetary and atmospheric origin in the intensity of thermal neutrons and to isolate changes caused by seismic processes.

 We used this method for analysis of thermal neutrons intensity during earthquakes with intensity ≥ 3b in the vicinity of Almaty which took place in 2007-2018. The catalog includes 30 events. The increase of thermal neutrons flux was observed for ~ 60% of events. However, before the earthquake the increase of thermal neutron flux is only observed for ~ 25-30% of events. The amplitude of the additional thermal neutron flux of the lithospheric origin is equal to 5-7% of the background level. Sometimes it reaches values of 10-12%.

The analysis of our catalog of earthquakes in the vicinity of Almaty also showed that 70% of these events occurred during the full moon or new moon (+/- 2 days).

How to cite: Antonova, V., Kryukov, S., Lutsenko, V., and Malimbaev, A.: Study of changes of thermal neutrons intensity of lithospheric origin for the diagnostics and forecast of earthquakes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4402, https://doi.org/10.5194/egusphere-egu2020-4402, 2020.

Several subduction zones exists in Earth, which have a more or less known dynamic, however each of them has its particularities, as in the case of the Mexican subduction zone, where the flat slab is of special interest. The present flat-slab area is located along the central part of the Cocos-North America plate boundary that the convergence rate between Cocos and North America. The Cocos plate is a remnant of the large Farallon plate, which began to split into smaller plates since 28 Myr ago approximately, when the East Pacific Rise began to interact with the North American Plate. Within such flat slab could be trigger large and destructives earthquakes like the main shock occurred close to Mexico City on September 19, 2017. In this work, we analyze, under the natural time domain, the seismicity registered within the Mexican flat slab since 1995 until the main shock occurred on September 19, 2017. We analyzed the fluctuations of order parameter for seismicity in order to provide some complex measures defined on natural time. Our analysis reveals a possible precursor measure switching on a few weeks before the main shock.  Also we have observed that in the flat slab region the number of earthquakes recorded is lesser than those observed along the total south Pacific Mexican coast.

How to cite: Ramírez-Rojas, A. and Flores-Márquez, E. L.: Complexity measures and variability of the seismicity monitored whithin the Mexican flat slab before the main shock occurred on 19 September 2017, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6184, https://doi.org/10.5194/egusphere-egu2020-6184, 2020.

Several YRY-4 borehole strainmeters have been installed in Sichuan province, China, aiming at monitoring the crustal activities associated with earthquakes. In order to verify the existence of strain precursors preceding the Lushan earthquake, we investigate the negentropy of the borehole strain data during 2011-2013.

First, some local factors that could affect the strain are ruled out, such as environmental disturbances, we analyze the strain responses to air pressure as well as solid tides and water level which were recorded on one YRY-4 strainmeter. Based on a state-space model according to the observations of the strainmeter, we remove the strain response to air pressure, in addition to those due to water level changes and the solid tides by Kalman filter. To investigate whether the remained strain changes are related to the Lushan earthquake, we introduce the approximate negentropy as an easily computable non-randomness measure to give evidence of strain changes and illustrate the instability of the underground of the earthquake zone. Generally, the appearance of a pre-catastrophic state can be characterized by significant higher non-randomness in terms of approximate negentropy.

Negentropy analysis of 3 stations of the southwest end of the Longmenshan fault zone have been performed. The nearest GZ station is 77 km away from the epicenter, and the epicenter distances of XM and RH are respectively 270 and 436 km. The statistical results at GZ station of cumulative counts of negentropy anomaly show acceleration about 6 to 4 months and 10 days prior to the earthquake, implying there are non-random changes in the borehole strain data, which is similar to the previous results. In addition, after the earthquake, the anomalies increase briefly and recover to a quiet state. Besides, XM station appears a significant surge from October 2012 to 2013, which is consistent with the first period anomaly extracted from the GZ station. However, RH station doesn’t show anomaly acceleration, probably due to the distance.

Furthermore, we compare the anomaly acceleration rate of each station. The results indicate that as the epicenter distance increases, the acceleration rate becomes less significant, suggesting the negentropy anomalies are more sensitive near the Lushan earthquake epicenter. In other words, the anomalies of the borehole strain data dependent on the epicenter distance. Therefore, we conclude that there may be strain precursors before the Lushan earthquake and the negentropy analysis have potential capability in the study of earthquake precursors.

How to cite: Yu, Z., Hattori, K., Zhu, K., Chi, C., and Fan, M.: Negentropy anomaly analysis of the borehole strain data associated with the Ms 7.0 Lushan earthquake, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6700, https://doi.org/10.5194/egusphere-egu2020-6700, 2020.

In terms of geodynamic life, territory of Georgia is one of the most active region. The macro structural factor here is represented by the contact with the Arabian and Eurasian tectonic plates, which in addition to the geological diversity of the area conditions the high seismicity of mentioned region. 

More the 20 year was operating a special network of hydro-geodynamical (water level, Atmosphere pressure and air temperature) observation on the territory of Georgia. Ten deep boreholes located basically on the main geo-plate and open deep aquifers. These wells as sensitive strain-meters recorded all kinds of deformation caused by exogenous (atmospheric pressure, tidal variations and season variation), as well as endogenous processes.

During observation on the territory of Georgia has observed various anomalies by water level before seismic events. Revealing of the mechanism of interrelation between the deformation processes, forestall strong earthquakes, and a hydrodynamic variation of underground waters, would allow to explain such preliminary behavior of hydrodynamic effects and to develop scientifically proven methods of the forecast of earthquakes.

How to cite: Jimsheladze, T., Kereselidze, Z., Melikadze, G., and Kobzev, G.: Variation of geophysical parameters during preparation of seismic events, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7816, https://doi.org/10.5194/egusphere-egu2020-7816, 2020.

Santorini's caldera being unrest during 2011-2012, led several studies to raise the important question of whether seismicity is associated with an impending and potential volcanic eruption or it solely relieves the accumulated tectonic energy. In the present work we study seismic coda waves generated by local earthquake events prior, during and after the seismic crisis that occurred within the caldera area. Coda waves are interpreted as scattered seismic waves generated by heterogeneities within the Earth, i.e. by faults, fractures, velocity and/or density boundaries and anomalies, etc. In particular, we utilize the three components of the seismograms recorded by three seismological stations on the island of Santorini and estimate the duration of the coda waves by implementing a three step procedure that includes the signal-to-noise ratio, the STA/LTA method and the short time Fourier transform. The final estimation was verified or reestimated manually due to the existent ambient seismic noise. Due to the nature and the path complexity of the coda waves and towards achieving a unified framework for the study of the immerse geo-structural seismotectonic complexity of the Santorini volcanic complex, we use Non-Extensive Statistical Physics (NESP) to study the probability distribution functions (pdfs) of the increments of seismic coda waves. NESP forms a generalization of the Boltzmann-Gibbs statistical mechanics, that has been extensively used for the analysis of semi-chaotic systems that exhibit long-range interactions, memory effects and multi-fractality. The analysis and results demonstrate that the seismic coda waves increments deviate from the Gaussian shape and their respective pdfs could adequately be described and processed by the q-Gaussian distribution. Furthermore and in order to investigate the dynamical structure of the volcanic-tectonic activity, we estimate the q-indices derived from the pdfs of the coda wave time series increments during the period 2009 - 2014 and present their variations as a function of time and as a function of the local magnitude (M_L) of the events prior, during and after the caldera unrest.

 Acknowledgments. We acknowledge support by the project “HELPOS – Hellenic System for Lithosphere Monitoring” (MIS 5002697) which is implemented under the Action “Reinforcement of the Research and Innovation Infrastructure”, funded by the Operational Programme "Competitiveness, Entrepreneurship and Innovation" (NSRF 2014-2020) and co-financed by Greece & European Union (ERDF)

How to cite: Aspiotis, T., Koutalonis, I., Michas, G., and Valianatos, F.: Dynamical evolution of the seismic coda wave increments during the 2011-2012 Santorini's caldera unrest. A Non-Extensive Statistical Physics approach., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8190, https://doi.org/10.5194/egusphere-egu2020-8190, 2020.

In this study we investigate volcanic eruption phenomena related to ionospheric disturbances, e.g. Heki (2006) used total electron content (TEC) measurements for this task. In particular, a model is developed how discharge phenomena (e.g. Houghton etal, 2013) can produce magnetic field variations at SWARM and CSES satellite orbits, i.e. altitudes of ~500 km in the F-region. Several coupling mechanism between lithosphere, atmosphere, and ionosphere are discussed by Simões etal (2012).
Experimental evidence is based on magnetic field observations aboard CSES mission in the time frame July 2018 to January 2019. The theoretical considerations include the source mechanism, propagation path, and the signal strength at low earth orbit satellite altitude.

Ref:
(1) Heki, K., Explosion energy of the 2004 eruption of the Asama Volcano, central Japan, inferred from ionospheric disturbances, GRL, 33, L14303, 2006. doi:10.1029/2006GL026249
(2) Houghton, I. M. P., K. L. Aplin, and K. A. Nicoll, Triboelectric Charging of Volcanic Ash from the 2011 Grı́msvötn Eruption, PRL, 111, 118501, 2013. doi:10.1103/PhysRevLett.111.118501 arXiv:1304.1784
(3) Simões F., R. Pfaff, J.-J. Berthelier, J. Klenzing, A Review of Low Frequency Electromagnetic Wave Phenomena Related to Tropospheric-Ionospheric Coupling Mechanisms, SSR, 168:551–593, 2012. doi:10.1007/s11214-011-9854-0

How to cite: Schwingenschuh, K., Magnes, W., Shen, X., Wang, J., Cheng, B., Pollinger, A., Hagen, C., Lammegger, R., Ellmeier, M., Schirninger, C., Eichelberger, H.-U., Mandl, B., Boudjada, M. Y., Besser, B. P., Rozhnoi, A. A., Zhang, T., Delva, M., Jernej, I., Aydogar, Ö., and Leonhardt, R.: Satellite and ground-based magnetic field observations related to volcanic eruptions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8882, https://doi.org/10.5194/egusphere-egu2020-8882, 2020.

In this work we analyse variations in VLF/LF radio signal amplitudes recorded by the INFREP network in the period 16 November – 6 December, 2019 characterized by very intensive seismic activities in the Balkan peninsula, Crete, and Adriatic, Aegean and Black seas. Namely, 38 earthquakes with magnitude greater than 4.0 occurred in this area during the noticed period; the most intensive of them occurred on 26 and 27 November: three events in Albania (M_w= 6.4, 5.3, 5.1), one in Crete (M_w= 6), one in Bosnia and Herzegovina (M_w= 5.4) and two in Adriatic sea (M_w= 5.4, 5.3). We study both long- and short- term variations that are already recorded in earlier studies. The long-term variations relate to changes in the amplitude intensities in periods of several days and their existence is shown in many previous studies. The recent analyses also indicate short-term variations in signal amplitude noises started about several tents of minutes before the earthquake (Nina et al. 2020). In this work, we analyse different areas using INFREP network, which allow us to study local changes in the atmosphere. In order to examine possible precursors we considered longer time started and ended 10 days before and after the most intensive of the considered earthquakes, respectively.

This research is supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia, under the projects 176002 and III44002.

References

Nina, A., S. Pulinets, P. F. Biagi, G. Nico, S. T. Mitrović, M. Radovanović and L. Č. Popović. Science of the Total Environment 710 (2020) 136406

How to cite: Biagi, P. F., Nina, A., Ermini, A., and Nico, G.: Variations revealed by INFREP Radio Network in correspondence of six earthquakes with MW greater than 5.0 occurred in the Balkan Peninsula and Adriatic Sea on 26 and 27 November, 2019, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9200, https://doi.org/10.5194/egusphere-egu2020-9200, 2020.

The China Seismo-Electromagnetic Satellite (CSES) was successfully launched on February 2, 2018. Its main scientific objective is to monitor earthquake related disturbances in the ionosphere. The Global Navigation Satellite System (GNSS) Radio Occultation Receiver (GOR) on board the satellite is able to observe the occultation events of Global Positioning System (GPS) and BeiDou navigation satellite System(BDS). Compared to some conventional observation means, GOR has the advantages of low cost, high accuracy, high precision, high vertical resolution, all-weather sounding, long-term constant and global coverage. The GOR on CSES can receive about 600 ionosphere occultation events each day and 16000 each month. The strip-shaped spatial distributions of the ionospheric characteristic parameters from the GOR show that the values of NmF₂ and HmF₂ are larger in the areas of the equator than in middle and high latitude areas.

How to cite: Xu, S., ZeRen, Z., Huang, J., Shen, X., Chu, W., Yan, R., Cui, J., and Lin, J.: Preliminary Results of GNSS Radio Occultation Receiver onboard CSES, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12340, https://doi.org/10.5194/egusphere-egu2020-12340, 2020.

We report on VLF/LF transmitter signals observed in the year 2018 during the minimum of solar activity. Those signals were recorded in Graz (Austria) using INFREP (Biagi et al., Nat. Hazards Earth Syst. Sci., 11, 2011) and UltraMSK (Schwingenschuh et al., Nat. Hazards Earth Syst. Sci., 11, 2011) systems. This leads us to record fourteen transmitter signals in the frequency range between 19 kHz and up to 270 kHz. Six transmitter channels are common to both systems and are localized in Great-Britain (Anthorn, GBZ, 19.58kHz), Italy (Tavolara, ICV, 20.27kHz), Germany (Rhauderfehn, 23.4kHz,) and Island (Keflavik, NRK, 37.5kHz). Others are mainly LF broadcasting transmitters from Romania (Brasov, 153kHz), Luxembourg (Felsberg-Berus, 183kHz), Algeria (Berkaoui, 198kHz), Monte-Carlo (Roumoules, 216kHz) and Tchecki (Lualualei, 270kHz). In the year 2018, the solar activity decreased reaching its minimum in the end of 2019. We emphasize in this work on three aspects: (a) C-flares related to the solar activity, (b) Kp-index linked to the geomagnetic activity, and (c) seismic events in the southern part of Europe, i.e. Greece and Italy.  The dominant patterns observed on almost all transmitters are due to the solar flares. Geomagnetic activity is found to depend on the seasonal effect and mainly observed few weeks before and after the summer solstice in the northern hemisphere.  Few earthquakes occurred in the southern part of Europe, in Greece (6 events) and in Italy (2 events) with a magnitude of 5.5 Mw and depths less than 10 km. We discuss the disturbances of VLF/LF transmitter signals prior to EQs occurrences, and their links to external effects. Our results are compared to recent investigations of Zhang et al. (Radio Sci., 52, 2017) and Rozhnoi et al. (Ann. Geophys., 37, 2019) concerning, respectively, the spatial distribution of VLF transmitter signals recorded by Demeter satellite, and the solar X-flare effects on VLF/LF transmitter signals.

How to cite: Boudjada, M. Y., Weingril, V., Eichelberger, H. U., Biagi, P. F., Zhang, X., Magnes, W., Schwingenschuh, K., Rozhnoi, A., Galopeau, P. H. M., Ermini, A., Lammer, H., Colella, R., Besser, B., and Stachel, M.: Analysis of VLF/LF transmitter signals during the minimum of solar activity in the year 2018, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13456, https://doi.org/10.5194/egusphere-egu2020-13456, 2020.

The last two decades a significant effort has been invested in order to understand and interpret the link between seismic activity and ionospheric perturbations. Since not any individual seismo-ionospheric precursor can be used as an accurate stand alone for earthquake prediction it is required to integrate different kinds of precursors and analysis techniques.

To this context, the aim of this study is to investigate pre-earthquake ionospheric anomalies that occurred prior to large 6.4 Mw earthquake in Albania (26^th November 2019), following a multi-instrument and multi-technique approach, using subionospheric radio VLF/LF signals obtained from the Romanian receivers of the INFREP European network and Total Electron Content (TEC) observations from GNSS global network.

To identify possible ionospheric anomalies before the earthquakes we applied the terminator time and nighttime fluctuation methods on the amplitude of subionospheric LF radio signals and spectral analysis on diurnal TEC variations several days prior the seismic event. It was found that sunrise terminator times are delayed approximately 20-40 min few days before and during the earthquake day. Intensified wave-like TEC oscillations with periods around 20 min were also revealed up to 5 days prior to the earthquake shocks in all cases that could be interpreted as possible ionospheric precursors of the impending earthquakes.      

How to cite: Moldovan, I. A., Toader, V. E., Oikonomou, C., Haralambous, H., Biagi, P. F., Muntean, A., Mihai, A., and Khadka, A.: Investigation Of Pre-Earthquake Ionospheric Anomalies Before Albania 2019 Earthquake Using The Romanian Receivers Of The Vlf/Lf Infrep And Gnss Global European Networks, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13952, https://doi.org/10.5194/egusphere-egu2020-13952, 2020.

In this study we present measurements and simulations of mid-latitude sub-ionospheric propagation paths between several VLF/LF transmitters and the Graz seismo-electromagnetic receiver facility (Schwingenschuh etal, 2011) during the current solar minimum condition. The upper D/E-region boundary of the waveguide is stable during the low solar activity in the years 2018 and 2019, i.e. measured VLF/LF amplitude and phase variations are mainly due to natural excitations from the lithosphere, atmosphere, and man-made disturbances. In particular, this period gives a baseline to characterize VLF amplitude and phase modulations in the waveguide cavity related to seismic activity over Europe. In addition, this opportunity let us probe the signal threshold and feed-back into waveguide simulation models. We conclude, proven long-term VLF/LF measurements, the continuous monitoring of the cavity, could be valuable in the assessment of seismic hazard scenarios.

Ref:

Schwingenschuh, K., Prattes, G., Besser, B. P., Mocnik, K., Stachel, M., Aydogar, Ö., Jernej, I., Boudjada, M. Y., Stangl, G., Rozhnoi, A., Solovieva, M., Biagi, P. F., Hayakawa, M., and Eichelberger, H. U.: The Graz seismo-electromagnetic VLF facility, Nat. Hazards Earth Syst. Sci., 11, 1121–1127, https://doi.org/10.5194/nhess-11-1121-2011, 2011.

How to cite: Eichelberger, H., Schwingenschuh, K., Boudjada, M. Y., Besser, B. P., Wolbang, D., Rozhnoi, A., Solovieva, M., Biagi, P. F., Stachel, M., Aydogar, Ö., Muck, C., Grill, C., and Jernej, I.: Characterization of sub-ionospheric VLF/LF waveguides for seismic event studies during solar minimum, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-15760, https://doi.org/10.5194/egusphere-egu2020-15760, 2020.

The seismo-ionospheric interaction study with respect to earthquake events using Total Electron Content (TEC) data derived from Global Navigation Satellite Systems (GNSS) receivers can be used to detect pre-earthquake ionospheric anomalies. This is primarily because ionospheric anomaly variation has been emerged as one of the most promising precursors. In recent times, many studies have reported pre-seismic ionospheric anomalies of TEC prior to major earthquakes. However, the results are not uniform and therefore, considerable amount of data processing and validation is required before this can be used in operational mode.  To ensure the seismogenic cause of TEC variation, geomagnetic and solar-activities are also compared with TEC values prior to the earthquakes and our analysis has proved that TEC anomalies can be used as earthquake precursors. Several global events and Himalayan earthquakes have been studied and results are very encouraging for developing a methodology that can qualify for detection of early sign of earthquakes. It may be far from early warning system (EWS) with information on magnitude, location and time, but it is a significant achievement in the field of earthquake geology where no methodology exists on forewarning of seismic events.

 Seismic velocity changes computed by applying modern techniques in seismic interferometry reveals that considerably large earthquakes can trigger a decline in seismic velocity prior to the mainshock. Cross-correlation of diffuse wave fields, including ambient seismic noise can provide the Green’s function between pair of receivers recording seismic activity. Using the known properties of the seismic ambient noise, recorded over a large period of time, seismic velocity changes before the earthquake has been observed which can act as a potential precursor. Decrease in the seismic velocity few days before the main event suggest that co-seismic damage begins to occur even before the mainshock, which could be a result of foreshocks. The main shock records the lowest relative seismic velocity change. The potential use of the ambient noise as an earthquake precursor can be concluded after rigorous analysis.

How to cite: Sahu, S., Borah, K., and Champati ray, P. K.: Total Electron Content and Seismic Ambient Noise analysis prior to significant earthquakes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19124, https://doi.org/10.5194/egusphere-egu2020-19124, 2020.

Since 2001, Robust Satellite Techniques (RST; Tramutoli 1998, 2007) has been used to study - by analyzing long-term TIR observations provided by passive satellite sensors - the enhancement of the Earth thermally emitted radiation, possibly related to seismic activities.

Such an approach has demonstrated to be able (especially when applied to geostationary satellite radiances) to isolate TIR anomalies possibly related to earthquake occurrence from those expected as a consequence of others natural (e.g. meteorological) or observational (e.g. measurement time and/or place) sources. Among the others TIR anomalies, those more significant (in term of Signal/Noise ratio), extended (in space) and persistent (in time) have been considered (SSTAs, Significant Sequence of TIR Anomalies, Eleftheriou et al., 2016) for further analyses. Up to now, long-term statistical correlation analyses between seismic events and RST-based SSTAs carried out in different European seismic regions (i.e. Greece, Italy and Turkey by using MSG-SEVIRI) highlights that the 75% of SSTAs are in apparent space-time relation with earthquakes with magnitude greater than 4. In all testing regions/periods a non-casual relation has been found.

In this paper, we will show the results achieved by real-time thermal monitoring over Albania region at time of the strong earthquake of magnitude Mw 6.4 occurred on 26 November 2019. Moreover, we will discuss about the impact of the use of the "RST-based satellite TIR anomalies" parameter in the framework a multi-parametric system devote to the seismic hazard assessment in the short-term.

How to cite: Tramutoli, V., Genzano, N., Colonna, R., Filizzola, C., Lisi, M., Pergola, N., and Satriano, V.: Satellite thermal monitoring of Balkan region by means of Robust Satellite Techniques: the case of Albania (26 November 2019, Mw 6.4) earthquake, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9068, https://doi.org/10.5194/egusphere-egu2020-9068, 2020.