{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,16]],"date-time":"2026-05-16T16:11:57Z","timestamp":1778947917877,"version":"3.51.4"},"reference-count":79,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2021,5,27]],"date-time":"2021-05-27T00:00:00Z","timestamp":1622073600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"DST\/SERB","award":["EMR\/2016\/003889"],"award-info":[{"award-number":["EMR\/2016\/003889"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Entropy"],"abstract":"<jats:p>In this work we present the statistical and criticality analysis of the very low frequency (VLF) sub-ionospheric propagation data recorded by a VLF\/LF radio receiver which has recently been established at the University of West Attica in Athens (Greece). We investigate a very recent, strong (M6.9), and shallow earthquake (EQ) that occurred on 30 October 2020, very close to the northern coast of the island of Samos (Greece). We focus on the reception data from two VLF transmitters, located in Turkey and Israel, on the basis that the EQ\u2019s epicenter was located within or very close to the 5th Fresnel zone, respectively, of the corresponding sub-ionospheric propagation path. Firstly, we employed in our study the conventional analyses known as the nighttime fluctuation method (NFM) and the terminator time method (TTM), aiming to reveal any statistical anomalies prior to the EQ\u2019s occurrence. These analyses revealed statistical anomalies in the studied sub-ionospheric propagation paths within ~2 weeks and a few days before the EQ\u2019s occurrence. Secondly, we performed criticality analysis using two well-established complex systems\u2019 time series analysis methods\u2014the natural time (NT) analysis method, and the method of critical fluctuations (MCF). The NT analysis method was applied to the VLF propagation quantities of the NFM, revealing criticality indications over a period of ~2 weeks prior to the Samos EQ, whereas MCF was applied to the raw receiver amplitude data, uncovering the time excerpts of the analyzed time series that present criticality which were closest before the Samos EQ. Interestingly, power-law indications were also found shortly after the EQ\u2019s occurrence. However, it is shown that these do not correspond to criticality related to EQ preparation processes. Finally, it is noted that no other complex space-sourced or geophysical phenomenon that could disturb the lower ionosphere did occur during the studied time period or close after, corroborating the view that our results prior to the Samos EQ are likely related to this mainshock.<\/jats:p>","DOI":"10.3390\/e23060676","type":"journal-article","created":{"date-parts":[[2021,5,27]],"date-time":"2021-05-27T23:16:46Z","timestamp":1622157406000},"page":"676","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":23,"title":["Statistical and Criticality Analysis of the Lower Ionosphere Prior to the 30 October 2020 Samos (Greece) Earthquake (M6.9), Based on VLF Electromagnetic Propagation Data as Recorded by a New VLF\/LF Receiver Installed in Athens (Greece)"],"prefix":"10.3390","volume":"23","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-9044-2555","authenticated-orcid":false,"given":"Dimitrios Z.","family":"Politis","sequence":"first","affiliation":[{"name":"Department of Electrical and Electronics Engineering, Ancient Olive Grove Campus, University of West Attica, 12244 Egaleo, Greece"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5928-4587","authenticated-orcid":false,"given":"Stelios M.","family":"Potirakis","sequence":"additional","affiliation":[{"name":"Department of Electrical and Electronics Engineering, Ancient Olive Grove Campus, University of West Attica, 12244 Egaleo, Greece"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yiannis F.","family":"Contoyiannis","sequence":"additional","affiliation":[{"name":"Department of Electrical and Electronics Engineering, Ancient Olive Grove Campus, University of West Attica, 12244 Egaleo, Greece"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Sagardweep","family":"Biswas","sequence":"additional","affiliation":[{"name":"Indian Centre for Space Physics, 43 Chalantika, Garia St. Road, Kolkata 700084, India"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Sudipta","family":"Sasmal","sequence":"additional","affiliation":[{"name":"Indian Centre for Space Physics, 43 Chalantika, Garia St. Road, Kolkata 700084, India"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Masashi","family":"Hayakawa","sequence":"additional","affiliation":[{"name":"Hayakawa Institute of Seismo-Electromagnetics Co. Ltd. (Hi-SEM), University of Electro-Communications (UEC) Alliance Center #521, Kojimacho, Chofu, Tokyo 182-0026 1-1-1, Japan"},{"name":"Advanced Wireless and Communications Research Center (AWCC), University of Electro-Communications (UEC), Chofugaoka, Chofu, Tokyo 182-8585 1-5-1, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2021,5,27]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Hayakawa, M. (2015). Earthquake Prediction with Radio Techniques, John Willey and Sons.","DOI":"10.1002\/9781118770368"},{"key":"ref_2","first-page":"1","article-title":"Seismogenic Effects in ULF\/ELF\/VLF Electromagnetic Waves","volume":"6","author":"Hayakawa","year":"2019","journal-title":"Int. J. Elect. Appl. Res."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"7352","DOI":"10.1073\/pnas.072208499","article-title":"Electric and Magnetic Phenomena Observed Before the Volcano-Seismic Activity in 2000 in the Izu Island Region, Japan","volume":"99","author":"Uyeda","year":"2002","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"205","DOI":"10.1016\/j.tecto.2008.07.019","article-title":"Short-Term Earthquake Prediction: Current Status of Seismo-Electromagnetics","volume":"470","author":"Uyeda","year":"2009","journal-title":"Tectonophysics"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"391","DOI":"10.2183\/pjab.89.391","article-title":"On Earthquake Prediction in Japan","volume":"89","author":"Uyeda","year":"2013","journal-title":"P. Jpn. Acad. B-Phys."},{"key":"ref_6","unstructured":"Molchanov, O.A., and Hayakawa, M. (2008). Seismo-Electromagnetics and Related Phenomena: History and Latest Results, TERRAPUB."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"44","DOI":"10.29382\/eqs-2018-0005-5","article-title":"Seismic Electric Signals in Seismic Prone Areas","volume":"31","author":"Sarlis","year":"2018","journal-title":"Earthq. Sci."},{"key":"ref_8","unstructured":"Chelidze, T., Vallianatos, F., and Telesca, L. (2018). Four-Stage Model of Earthquake Generation in Terms of Fracture-Induced Electromagnetic Emissions: A Review. Complexity of Seismic Time Series., Elsevier."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"151","DOI":"10.1140\/epjst\/e2020-000249-x","article-title":"Evidence of Critical Dynamics in Various Electromagnetic Precursors","volume":"230","author":"Potirakis","year":"2021","journal-title":"Eur. Phys. J. Spec. Top."},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Varotsos, P.A., Sarlis, N.V., and Skordas, E.S. (2011). Natural Time Analysis: The New View of Time, Springer.","DOI":"10.1007\/978-3-642-16449-1"},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Hayakawa, M., Kasahara, Y., Nakamura, T., Muto, F., Horie, T., Maekawa, S., Hobara, Y., Rozhnoi, A.A., Solovieva, M., and Molchanov, O.A. (2010). A Statistical Study on the Correlation Between Lower Ionospheric Perturbations as Seen by Sub-Ionospheric VLF\/LF Propagation and Earthquakes. J. Geophys. Res., 115.","DOI":"10.1029\/2009JA015143"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"383","DOI":"10.4236\/ojer.2020.95022","article-title":"Contaminated Effect of Geomagnetic Storms on Pre-Seismic Atmospheric and Ionospheric Anomalies during Imphal Earthquake","volume":"9","author":"Biswas","year":"2020","journal-title":"OJER"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"371","DOI":"10.1016\/j.jseaes.2010.03.005","article-title":"Lithosphere\u2013Atmosphere\u2013Ionosphere Coupling (LAIC) model\u2014An Unified Concept for Earthquake Precursors Validation","volume":"41","author":"Pulinets","year":"2011","journal-title":"J. Asian Earth Sci."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"286","DOI":"10.1016\/S0375-9601(00)00180-8","article-title":"Criticality and Intermittency in the Order Parameter Space","volume":"268","author":"Contoyiannis","year":"2000","journal-title":"Phys. Lett. A."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"035701","DOI":"10.1103\/PhysRevLett.89.035701","article-title":"Intermittent Dynamics of Critical Fluctuations","volume":"89","author":"Contoyiannis","year":"2002","journal-title":"Phys. Rev. Lett."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"031138","DOI":"10.1103\/PhysRevE.76.031138","article-title":"Unimodal Maps and Order Parameter Fluctuations in the Critical Region","volume":"76","author":"Contoyiannis","year":"2007","journal-title":"Phys. Rev. E."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"397","DOI":"10.1016\/j.pce.2003.11.012","article-title":"Intermittent Dynamics of Critical Pre-Seismic Electromagnetic Fluctuations","volume":"29","author":"Contoyiannis","year":"2004","journal-title":"Phys. Chem. Earth Parts A\/B\/C"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"098101","DOI":"10.1103\/PhysRevLett.93.098101","article-title":"Criticality in the Relaxation Phase of a Spontaneously Contracting Atria Isolated from a Frogs Heart","volume":"93","author":"Contoyiannis","year":"2004","journal-title":"Phys. Rev. Lett."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"40","DOI":"10.1016\/j.jog.2014.09.015","article-title":"Tricritical Crossover in Earthquake Preparation by Analyzing Pre-Seismic Electromagnetic Emissions","volume":"84","author":"Contoyiannis","year":"2015","journal-title":"J. Geodyn."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"19","DOI":"10.1016\/j.physa.2016.01.065","article-title":"Intermittent Criticality Revealed in ULF Magnetic Fields Prior to the 11 March 2011 Tohoku Earthquake (MW = 9)","volume":"452","author":"Contoyiannis","year":"2016","journal-title":"Phys. A"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"023117","DOI":"10.1063\/1.4807908","article-title":"Natural Time Analysis of Critical Phenomena: The Case of Pre-Fracture Electromagnetic Emissions","volume":"23","author":"Potirakis","year":"2013","journal-title":"Chaos"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"631","DOI":"10.1109\/LGRS.2014.2354374","article-title":"Recent Field Observations Indicating an Earth System in Critical Condition Before the Occurrence of a Significant Earthquake","volume":"12","author":"Potirakis","year":"2015","journal-title":"IEEE Geosci. Remote Sens. Lett."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"223","DOI":"10.5194\/npg-23-223-2016","article-title":"Recent seismic activity at Cephalonia (Greece): A Study through Candidate Electromagnetic Precursors in Terms of Non-Linear Dynamics","volume":"23","author":"Potirakis","year":"2016","journal-title":"Nonlinear Proc. Geophys."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"422","DOI":"10.1016\/j.tecto.2017.11.020","article-title":"Intermittency-Induced Criticality in the Lower Ionosphere Prior to the 2016 Kumamoto Earthquakes as Embedded in the VLF Propagation Data Observed at Multiple Stations","volume":"722","author":"Potirakis","year":"2018","journal-title":"Tectonophysics"},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Potirakis, S., Asano, T., and Hayakawa, M. (2018). Criticality Analysis of the Lower Ionosphere Perturbations Prior to the 2016 Kumamoto (Japan) Earthquakes as Based on VLF Electromagnetic Wave Propagation Data Observed at Multiple Stations. Entropy, 20.","DOI":"10.3390\/e20030199"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"419","DOI":"10.1016\/j.jseaes.2017.12.036","article-title":"Natural Time Analysis on the Ultra-Low Frequency Magnetic Field Variations Prior to the 2016 Kumamoto (Japan) Earthquakes","volume":"154","author":"Potirakis","year":"2018","journal-title":"J. Asian Earth Sci."},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Potirakis, S., Schekotov, A., Contoyiannis, Y., Balasis, G., Koulouras, G., Melis, N., Boutsi, A., Hayakawa, M., Eftaxias, K., and Nomicos, C. (2019). On Possible Electromagnetic Precursors to a Significant Earthquake (Mw = 6.3) Occurred in Lesvos (Greece) on 12 June 2017. Entropy, 21.","DOI":"10.3390\/e21030241"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"563","DOI":"10.1016\/j.physa.2018.09.070","article-title":"Analysis of the Ultra-Low Frequency Magnetic Field Fluctuations Prior to the 2016 Kumamoto (Japan) Earthquakes in Terms of the Method of Critical Fluctuations","volume":"514","author":"Potirakis","year":"2019","journal-title":"Phys. A"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"121360","DOI":"10.1016\/j.physa.2019.121360","article-title":"L\u00e9vy and Gauss Statistics in the Preparation of an Earthquake","volume":"528","author":"Potirakis","year":"2019","journal-title":"Phys. A"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"47","DOI":"10.1007\/s11069-020-03910-3","article-title":"Criticality Analysis of 3-Year-Long VLF Sub-Ionospheric Propagation Data Possibly Related to Significant Earthquake Events in Japan","volume":"102","author":"Politis","year":"2020","journal-title":"Nat. Hazards"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"13734","DOI":"10.1073\/pnas.1312740110","article-title":"Minimum of the Order Parameter Fluctuations of Seismicity Before Major Earthquakes in Japan","volume":"110","author":"Sarlis","year":"2013","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_32","first-page":"25","article-title":"Criticality Features in Ulf Magnetic Fields Prior to the 2011 Tohoku Earthquake","volume":"91","author":"Hayakawa","year":"2015","journal-title":"P. Jpn. Acad. B Phys."},{"key":"ref_33","unstructured":"Ouzounov, D., Pulinets, S., Hattori, K., and Taylor, P. (2018). Very-Low\u2013to Low-Frequency Sounding of Ionospheric Perturbations and Possible Association with Earthquakes. Pre-Earthquake Processes: A Multidisciplinary Approach to Earthquake Prediction Studies., Wiley."},{"key":"ref_34","unstructured":"Hayakawa, M. (2013). VLF\/LF Signals Method for Searching of Electromagnetic Earthquake Precursors. Earthquake Prediction Studies: Seismo Electromagnetics., TERRAPUB."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"609","DOI":"10.1007\/s11589-011-0823-1","article-title":"Probing the Lower Ionospheric Perturbations Associated with Earthquakes by Means Of Sub-Ionospheric VLF\/LF Propagation","volume":"24","author":"Hayakawa","year":"2011","journal-title":"Earthq. Sci."},{"key":"ref_36","unstructured":"Hayakawa, M. (2009). Lower Ionospheric Perturbations Associated with Earthquakes, as Detected by Sub-Ionospheric VLF\/LF Radio Waves. Electromagnetic Phenomena Associated with Earthquakes, Transworld Research Network."},{"key":"ref_37","first-page":"169","article-title":"The Precursory Signature Effect of the Kobe Earthquake on VLF Sub-Ionospheric Signals","volume":"43","author":"Hayakawa","year":"1996","journal-title":"J. Comm. Res. Lab."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"1141","DOI":"10.3390\/s7071141","article-title":"VLF\/LF Radio Sounding of Ionospheric Perturbations Associated with Earthquakes","volume":"7","author":"Hayakawa","year":"2007","journal-title":"Sensors"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"239","DOI":"10.1016\/S0031-9201(97)00095-2","article-title":"Precursory Effects in the Sub-Ionospheric VLF Signals for the Kobe Earthquake","volume":"105","author":"Molchanov","year":"1998","journal-title":"Phys. Earth Planet. Inter."},{"key":"ref_40","doi-asserted-by":"crossref","unstructured":"Hayakawa, M., and Chakrabarti, S.K. (2010, January 13\u201318). The Use of Sub-Ionospheric VLF\u2215LF Propagation for the Study of Lower Ionospheric Perturbations Associated with Earthquakes. Proceedings of the Internet Conference on Science with Very Low Frequency Radio Waves: Theory and Observations, Kolkata, India.","DOI":"10.1063\/1.3512884"},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"333","DOI":"10.5194\/nhess-11-333-2011","article-title":"The European VLF\/LF Radio Network to Search for Earthquake Precursors: Setting Up and Natural\/Man-Made Disturbances","volume":"11","author":"Biagi","year":"2011","journal-title":"Nat. Hazards Earth Syst. Sci."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"101","DOI":"10.4236\/ojer.2019.82007","article-title":"The INFREP Network: Present Situation and Recent Results","volume":"08","author":"Biagi","year":"2019","journal-title":"Open J. Earthq. Res."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"2671","DOI":"10.5194\/nhess-14-2671-2014","article-title":"Meteorological Effects in the Lower Ionosphere as Based on VLF\/LF Signal Observations","volume":"14","author":"Rozhnoi","year":"2014","journal-title":"Nat. Hazards Earth Syst. Sci."},{"key":"ref_44","unstructured":"Chakrabarti, S.K. (2010, January 13\u201318). Propagation Effects of Very Low Frequency Radio Waves. Proceedings of the Internet Conference on Science with Very Low Frequency Radio Waves: Theory and Observations, Kolkata, India."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"115","DOI":"10.1080\/19475705.2010.486933","article-title":"Current Status of Seismo-Electromagnetics for Short-Term Earthquake Prediction","volume":"1","author":"Hayakawa","year":"2010","journal-title":"Geomat. Nat. Hazards Risk"},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"129","DOI":"10.5194\/nhess-8-129-2008","article-title":"On the Generation Mechanism of Terminator Times in Sub-Ionospheric VLF\/LF Propagation and Its Possible Application to Seismogenic Effects","volume":"8","author":"Yoshida","year":"2008","journal-title":"Nat. Hazards Earth Syst."},{"key":"ref_47","first-page":"314","article-title":"Possible Detection of Ionospheric Disturbances During the Sumatra-Andaman Islands Earthquakes of December, 2004","volume":"34","author":"Chakrabarti","year":"2005","journal-title":"Indian J. Radio Sp. Phys."},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"1403","DOI":"10.5194\/nhess-9-1403-2009","article-title":"Ionosperic Anomaly Due to Seismic Activities\u2014Part 1: Calibration of the VLF Signal of VTX 18.2 Khz Station from Kolkata and Deviation During Seismic Events","volume":"9","author":"Sasmal","year":"2009","journal-title":"Nat. Hazards Earth Syst. Sci."},{"key":"ref_49","doi-asserted-by":"crossref","unstructured":"Sasmal, S., Chakrabarti, S.K., and Chakrabarti, S. (2010, January 13\u201318). Studies of the Correlation Between Ionospheric Anomalies and Seismic Activities in the Indian Subcontinent. Proceedings of the Internet Conference on Science with Very Low Frequency Radio Waves: Theory and Observations, Kolkata, India.","DOI":"10.1063\/1.3512885"},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"1787","DOI":"10.1016\/j.asr.2017.06.031","article-title":"Numerical Modeling of Possible Lower Ionospheric Anomalies Associated with Nepal Earthquake in May, 2015","volume":"60","author":"Chakraborty","year":"2017","journal-title":"Adv. Space Res."},{"key":"ref_51","first-page":"531","article-title":"Unusual Behavior of D-Region Ionization Time at 18.2khz During Seismically Active Days","volume":"81","author":"Chakrabarti","year":"2007","journal-title":"Indian J. Phys."},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"1751","DOI":"10.5194\/nhess-10-1751-2010","article-title":"Ionospheric Anomaly Due to Seismic Activities\u2014Part 2: Evidence from D-Layer Preparation and Disappearance Times","volume":"10","author":"Chakrabarti","year":"2010","journal-title":"Nat. Haz. Earth Syst. Sci."},{"key":"ref_53","doi-asserted-by":"crossref","unstructured":"Ray, S., Chakrabarti, S.K., Sasmal, S., Choudhury, A.K., and Chakrabarti, S.K. (2010, January 13\u201318). Correlelations Between the Anomalous Behaviour of the Ionosphere and the Seismic Events for VTX-MALDA VLF Propagation. Proceedings of the International Conference on Science with Very Low Frequency Radio Waves: Theory and Observations, Kolkata, India.","DOI":"10.1063\/1.3512887"},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"2699","DOI":"10.5194\/nhess-11-2699-2011","article-title":"Ionospheric Anomaly Due to Seismic Activities-III: Correlation Between Night Time VLF Amplitude Fluctuations and Effective Magnitudes of Earthquakes in Indian Sub-Continent","volume":"11","author":"Ray","year":"2011","journal-title":"Nat. Hazards Earth Syst. Sci."},{"key":"ref_55","doi-asserted-by":"crossref","first-page":"85","DOI":"10.1007\/s12648-012-0014-5","article-title":"Precursory Effects in the Nighttime VLF Signal Amplitude for the 18th January, 2011 Pakistan Earthquake","volume":"86","author":"Ray","year":"2012","journal-title":"Indian J. Phys."},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"1501","DOI":"10.5194\/nhess-13-1501-2013","article-title":"A Study of the Behavior of the Terminator Time Shifts Using Multiple VLF Propagation Paths During the Pakistan Earthquake (M = 7.2) of 18 January 2011","volume":"13","author":"Ray","year":"2013","journal-title":"Nat. Hazards Earth Syst. Sci."},{"key":"ref_57","doi-asserted-by":"crossref","first-page":"1013","DOI":"10.1007\/s12648-014-0520-8","article-title":"Unusual Behavior of Very Low Frequency Signal During the Earthquake at Honshu\/Japan on 11 March, 2011","volume":"88","author":"Sasmal","year":"2014","journal-title":"Indian J. Phys."},{"key":"ref_58","doi-asserted-by":"crossref","first-page":"167","DOI":"10.1080\/19475705.2016.1161666","article-title":"Studies of Seismo-Ionospheric Correlations Using Anomalies in Phase of Very Low Frequency Signal","volume":"8","author":"Pal","year":"2017","journal-title":"Geomat. Nat. Haz. Risk"},{"key":"ref_59","doi-asserted-by":"crossref","first-page":"1596","DOI":"10.1080\/19475705.2019.1595178","article-title":"Comparative Study of the Possible Lower Ionospheric Anomalies in Very Low Frequency (VLF) Signal During Honshu, 2011 and Nepal, 2015 Earthquakes","volume":"10","author":"Ghosh","year":"2019","journal-title":"Geomat. Nat. Haz. Risk"},{"key":"ref_60","doi-asserted-by":"crossref","first-page":"011902","DOI":"10.1103\/PhysRevE.66.011902","article-title":"Long-Range Correlations in the Electric Signals that Precede Rupture","volume":"66","author":"Varotsos","year":"2002","journal-title":"Phys. Rev. E"},{"key":"ref_61","doi-asserted-by":"crossref","first-page":"041103","DOI":"10.1103\/PhysRevE.72.041103","article-title":"Similarity of Fluctuations in Correlated Systems: The Case of Seismicity","volume":"72","author":"Varotsos","year":"2005","journal-title":"Phys. Rev. E"},{"key":"ref_62","first-page":"294","article-title":"Spatio-Temporal Complexity Aspects on the Interrelation Between Seismic Electric Signals and Seismicity","volume":"76","author":"Varotsos","year":"2001","journal-title":"Pract. Athens Acad."},{"key":"ref_63","doi-asserted-by":"crossref","first-page":"170601","DOI":"10.1103\/PhysRevLett.94.170601","article-title":"Origin of the Usefulness of the Natural-Time Representation of Complex Time Series","volume":"94","author":"Abe","year":"2005","journal-title":"Phys. Rev. Lett."},{"key":"ref_64","doi-asserted-by":"crossref","first-page":"031114","DOI":"10.1103\/PhysRevE.73.031114","article-title":"Entropy of Seismic Electric Signals: Analysis in the Natural Time Under Time Reversal","volume":"73","author":"Varotsos","year":"2006","journal-title":"Phys. Rev. E"},{"key":"ref_65","doi-asserted-by":"crossref","first-page":"28006","DOI":"10.1209\/0295-5075\/96\/28006","article-title":"Similarity of Fluctuations in Systems Exhibiting Self-Organized Criticality","volume":"96","author":"Sarlis","year":"2011","journal-title":"Europhys. Lett."},{"key":"ref_66","doi-asserted-by":"crossref","first-page":"331","DOI":"10.2183\/pjab.84.331","article-title":"Investigation of Seismicity After the Initiation of a Seismic Electric Signal Activity Until the Mainshock","volume":"84","author":"Sarlis","year":"2008","journal-title":"Proc. Jpn. Acad. Ser. B"},{"key":"ref_67","doi-asserted-by":"crossref","first-page":"839","DOI":"10.1103\/RevModPhys.84.839","article-title":"Statistical Physics of Fracture, Friction, and Earthquakes","volume":"84","author":"Kawamura","year":"2012","journal-title":"Rev. Mod. Phys."},{"key":"ref_68","doi-asserted-by":"crossref","first-page":"771","DOI":"10.5194\/npg-20-771-2013","article-title":"Current Challenges for Pre-Earthquake Electromagnetic Emissions: Shedding Light from Micro-Scale Plastic Flow, Granular Packings, Phase Transitions and Self-Affinity Notion of Fracture Process","volume":"20","author":"Eftaxias","year":"2013","journal-title":"Nonlinear Proc. Geoph."},{"key":"ref_69","doi-asserted-by":"crossref","first-page":"2381","DOI":"10.5194\/nhess-13-2381-2013","article-title":"On the Puzzling Feature of the Silence of Precursory Electromagnetic Emissions","volume":"13","author":"Eftaxias","year":"2013","journal-title":"Nat. Hazards Earth Syst. Sci."},{"key":"ref_70","doi-asserted-by":"crossref","first-page":"083208","DOI":"10.1088\/1742-5468\/aad6ba","article-title":"Signatures of the Symmetry Breaking Phenomenon in Pre-Seismic Electromagnetic Emissions","volume":"2018","author":"Contoyiannis","year":"2018","journal-title":"J. Stat. Mech."},{"key":"ref_71","doi-asserted-by":"crossref","unstructured":"Potirakis, S.M., Contoyiannis, Y., Eftaxias, K., Melis, N.S., and Nomicos, C. (2021). Post-Spontaneous-Symmetry-Breaking Power-Laws After a Very Strong Earthquake: Indication for the Preparation of a New Strong Earthquake or Not?. arXiv.","DOI":"10.1016\/j.physa.2021.126607"},{"key":"ref_72","doi-asserted-by":"crossref","first-page":"066123","DOI":"10.1103\/PhysRevE.71.066123","article-title":"Monitoring of a Pre-Seismic Phase from Its Electromagnetic Precursors","volume":"71","author":"Contoyiannis","year":"2005","journal-title":"Phys. Rev. E."},{"key":"ref_73","doi-asserted-by":"crossref","first-page":"125","DOI":"10.5194\/nhess-13-125-2013","article-title":"The Earth as a Living Planet: Human-Type Diseases in the Earthquake Preparation Process","volume":"13","author":"Contoyiannis","year":"2013","journal-title":"Nat. Hazards Earth Syst. Sci."},{"key":"ref_74","first-page":"34","article-title":"Intermittency in Stock Market Dynamics","volume":"9","author":"Ozun","year":"2014","journal-title":"J. Orthop. Trauma"},{"key":"ref_75","doi-asserted-by":"crossref","first-page":"042206","DOI":"10.1103\/PhysRevE.95.042206","article-title":"Intermittency-Induced Criticality in a Resistor-Inductor-Diode Circuit","volume":"95","author":"Potirakis","year":"2017","journal-title":"Phys. Rev. E"},{"key":"ref_76","doi-asserted-by":"crossref","first-page":"2343","DOI":"10.1111\/ejn.14117","article-title":"Traits of Criticality in Membrane Potential Fluctuations of Pyramidal Neurons in the CA 1 Region of Rat Hippocampus","volume":"48","author":"Kosmidis","year":"2018","journal-title":"Eur. J. Neurosci."},{"key":"ref_77","doi-asserted-by":"crossref","first-page":"4594","DOI":"10.1002\/2017JA025131","article-title":"Observation of Intermittency-Induced Critical Dynamics in Geomagnetic Field Time Series Prior to the Intense Magnetic Storms of March, June, and December 2015","volume":"123","author":"Balasis","year":"2018","journal-title":"J. Geophys. Res. Space Phys."},{"key":"ref_78","unstructured":"Schuster, H.G. (1995). Deterministic Chaos: An Introduction, VCH."},{"key":"ref_79","unstructured":"Huang, K. (1987). Statistical Mechanics, Wiley. [2nd ed.]."}],"container-title":["Entropy"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1099-4300\/23\/6\/676\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T06:09:16Z","timestamp":1760162956000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1099-4300\/23\/6\/676"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,5,27]]},"references-count":79,"journal-issue":{"issue":"6","published-online":{"date-parts":[[2021,6]]}},"alternative-id":["e23060676"],"URL":"https:\/\/doi.org\/10.3390\/e23060676","relation":{},"ISSN":["1099-4300"],"issn-type":[{"value":"1099-4300","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,5,27]]}}}