Recent seismic activity at Cephalonia (Greece): a study through candidate electromagnetic precursors in terms of non-linear dynamics

Abstract

Abstract. The preparation process of two recent earthquakes (EQs) that occurred in Cephalonia (Kefalonia), Greece, ((38.22 • N, 20.53 • E), 26 January 2014, M w = 6.0, depth ∼ 20 km) and ((38.25 • N, 20.39 • E), 3 February 2014, M w = 5.9, depth ∼ 10 km), respectively, is studied in terms of the critical dynamics revealed in observables of the involved non-linear processes. Specifically, we show, by means of the method of critical fluctuations (MCF), that signatures of critical, as well as tricritical, dynamics were embedded in the fracture-induced electromagnetic emissions (EMEs) recorded by two stations in locations near the epicentres of these two EQs. It is worth noting that both the MHz EMEs recorded by the telemetric stations on the island of Cephalonia and the neighbouring island of Zante (Zakynthos) reached a simultaneously critical condition a few days before the occurrence of each earthquake. The critical characteristics embedded in the EME signals were further verified using the natural time (NT) method. Moreover, we show, in terms of the NT method, that the foreshock seismic activity also presented critical characteristics before each event. Importantly, the revealed critical process seems to be focused on the area corresponding to the western Cephalonia zone, following the seismotectonic and hazard zoning of the Ionian Islands area near Cephalonia.

Entropy in Natural Time and the Associated Complexity Measures

“…The results show [67] that these criteria hold. The latter criteria have been also shown [68][69][70] to be valid for other EM emissions that preceded the strong earthquakes of 12 October 2013, 26 January 2014 and 3 February 2014 in Greece and the 2013 M = 6.3 earthquake at Kobe, Japan.…”

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

“…In a large number of relevant articles published during the last few decades a variety of electromagnetic (EM) phenomena have been reported to appear prior to an earthquake (EQ), e.g., [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ]. Specifically, the ionosphere has statistically been confirmed to be correlated with EQs in such a way that it presents remarkable sensitivity to EQ preparation processes happening in the lithosphere, e.g., [ 9 , 10 ].…”

“…The analysis is performed by means of the recently proposed natural time (NT) method [ 33 , 34 , 35 ]. Beyond the seismic electric signals (SES) of Varotsos’ group, the NT method has already been successfully applied on other EM variations possibly related to EQs, such as MHz-kHz EM emissions [ 8 , 36 , 37 ] and ground-observed ULF magnetic fields (e.g., [ 31 , 38 , 39 , 40 ]). Yet, this is the first attempt of application of NT analysis to VLF subionospheric propagation data.…”

Observation of Intermittency‐Induced Critical Dynamics in Geomagnetic Field Time Series Prior to the Intense Magnetic Storms of March, June, and December 2015

“…The recently proposed method of critical fluctuations (MCF) has specifically been developed for the analysis of time series sourced from thermal systems governed by nonlinear intermittent dynamics (Contoyiannis & Diakonos, ; Contoyiannis et al, ). MCF is capable of identifying the existence of critical state, implying second‐order phase transition in equilibrium, as well as the departure from it, while it has successfully been applied to a wide variety of dynamical systems ranging from theoretical thermal systems to geophysical, biological, electronic, and financial ones (Contoyiannis et al, ; Contoyiannis, Diakonos, Kapiris, et al, ; Contoyiannis, Diakonos, Papaefthimiou, & Theophilidis, ; Contoyiannis et al, , ; Ozun et al, ; Potirakis et al, , , , ). In the following we provide a brief presentation of the key theoretical aspects of MCF as well as a step‐by‐step procedure for its application to a time series.…”