On the recent seismic activity at eastern Aegean Sea: Analysis of fracture-induced electromagnetic emissions in terms of critical fluctuations

📝 Abstract

In this letter we show, in terms of fracture-induced electromagnetic emissions (EME) that the Earth system around the focal areas came to critical condition a few days before the occurrence of recent significant (M>5) earthquakes (EQs) which happened in the region of the eastern Aegean Sea, between the Greek Islands of Lesvos (6-7, 12 February 2017 and 12 June 2017) and Kos (20 July 2017) and the Turkish Asia Minor coastline. Moreover, departure from the critical state in terms of a tricritical crossover was identified in the EME recorded prior to the 12 June main event as well as prior to the 20 July main event. The analysis was performed by means of the method of critical fluctuations (MCF).

💡 Analysis

In this letter we show, in terms of fracture-induced electromagnetic emissions (EME) that the Earth system around the focal areas came to critical condition a few days before the occurrence of recent significant (M>5) earthquakes (EQs) which happened in the region of the eastern Aegean Sea, between the Greek Islands of Lesvos (6-7, 12 February 2017 and 12 June 2017) and Kos (20 July 2017) and the Turkish Asia Minor coastline. Moreover, departure from the critical state in terms of a tricritical crossover was identified in the EME recorded prior to the 12 June main event as well as prior to the 20 July main event. The analysis was performed by means of the method of critical fluctuations (MCF).

📄 Content

Contoyiannis et al. Preseismic electromagnetic emissions related to recent eastern Aegean Sea EQs. p. 1

On the recent seismic activity at eastern Aegean Sea: Analysis of fracture-induced electromagnetic emissions in terms of critical fluctuations.

Y. Contoyiannis1, S. M. Potirakis1, J. Kopanas2, G. Antonopoulos2,
G. Koulouras3, K. Eftaxias2, C. Nomicos3.

1. Department of Electronics Engineering, Piraeus University of Applied Sciences (TEI of Piraeus), 250 Thivon and P. Ralli, Aigaleo, Athens GR-12244, Greece, (Y.C: yiaconto@puas.gr; S.M.P.: spoti@puas.gr)
2. Department of Physics, Section of Solid State Physics, University of Athens, Panepistimiopolis, GR-15784, Zografos, Athens, Greece, (J.K.: jkopan@otenet.gr; G.A.: sv8rx@teiion.gr; Κ.Ε: ceftax@phys.uoa.gr)
3. Department of Electronics Engineering, Technological Educational Institute (TEI) of Athens, Ag. Spyridonos, GR-12210, Aigaleo, Athens, Greece, (G.K.: gregkoul@teiath.gr; C.N.: cnomicos@teiath.gr).

Abstract In this letter we show, in terms of fracture-induced electromagnetic emissions (EME) that the Earth system around the focal areas came to critical condition a few days before the occurrence of recent significant (M>5) earthquakes (EQs) which happened in the region of the eastern Aegean Sea, between the Greek Islands of Lesvos (6-7, 12 February 2017 and 12 June 2017) and Kos (20 July 2017) and the Turkish Asia Minor coastline. Moreover, departure from the critical state in terms of a tricritical crossover was identified in the EME recorded prior to the 12 June main event as well as prior to the 20 July main event. The analysis was performed by means of the method of critical fluctuations (MCF).

Keywords: Fracture-induced electromagnetic emissions; Earthquake; Criticality; Tricriticality; Greece. 1 Introduction The possible connection of the electromagnetic (EM) activity that is observed prior to significant earthquakes (EQs) with the corresponding EQ preparation processes, often referred to as seismo-electromagnetics, has been intensively investigated during the last years. Several possible EQ precursors have been suggested in the literature [Uyeda et al., 2009, 2013; Cicerone et al., 2009; Hayakawa, 2013a, 2013b, 2015]. The possible relation of the field observed fracture-induced electromagnetic emissions (EME) in the frequency bands of MHz and kHz has been examined in a series of publications [e.g., Eftaxias et al., 2001, 2004, 2008, 2013; Eftaxias and Potirakis, 2013; Contoyiannis et al., 2004a, 2005, 2010, 2013, 2015; Contoyiannis and Eftaxias, 2008; Kapiris et al., 2004; Karamanos et al., 2006; Papadimitriou et al., 2008; Potirakis et al., 2011, 2012a, 2012b, 2012c, 2013, 2015, 2016; Minadakis et al., 2012a, 2012b; Donner et al., 2015; Kalimeris et al., 2016], while a four-stage model for the preparation of an EQ by means of its observable EM activity has been recently put forward [Donner et al., 2015; Potirakis et al., 2016, and references therein]. In this letter, we report the recording, with a sampling rate of 1 sample/s, of MHz EME signals with critical characteristics of a second order phase transition in equilibrium before the EQs which happened in the region of the eastern Aegean Sea, between the Greek Islands of Lesvos (6-7, 12 February 2017 and 12 June 2017), and Kos (20 July 2017) and the Turkish Asia Minor coastline. Moreover, we report tricritical characteristics revealed in the kHz EME recorded prior to the 12 June main event, while tricritical characteristics present both MHz and kHz EME prior to the 20 July event. Note that, as expected, all trictitical Contoyiannis et al. Preseismic electromagnetic emissions related to recent eastern Aegean Sea EQs. p. 2

behaviors appear later than the corresponding MHz EME critical behavior. The transition from the critical to tricritical phase means that the system has departed from the equilibrium state. Furthermore, it has to be mentioned that no kHz signals of clearly high organization and persistency was possible to be validated, probably due to the fact that all the aforementioned EQs happened in the Sea or very close to it. We will further comment on this fact in the discussion-conclusion Section. The analysis of the specific EME time-series was performed using the method of critical fluctuations (MCF) [Contoyiannis and Diakonos, 2000; Contoyiannis et al., 2002, 2013, 2015; Potirakis et al., 2016]. The analysis reveals that first in the timeline appear critical features in the MHz EME, implying that the possibly related underlying fracture process involved in the preparation of the main shock is at critical state. The presence of the “critical point” during which any two active parts of the system are highly correlated even at arbitrarily long distances, in other words when “everything depends on everything else”, is consistent with the view that the EQ preparation process during the period that the MHz EM

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