Articles | Volume 23, issue 4
Nonlin. Processes Geophys., 23, 223–240, 2016
Nonlin. Processes Geophys., 23, 223–240, 2016

Research article 04 Aug 2016

Research article | 04 Aug 2016

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

Stelios M. Potirakis1, Yiannis Contoyiannis1, Nikolaos S. Melis2, John Kopanas3, George Antonopoulos3, Georgios Balasis4, Charalampos Kontoes4, Constantinos Nomicos5, and Konstantinos Eftaxias6 Stelios M. Potirakis et al.
  • 1Department of Electronics Engineering, Piraeus University of Applied Sciences (TEI of Piraeus), 250 Thivon and P. Ralli, Aigalao, Athens, 12244, Greece
  • 2Institute of Geodynamics, National Observatory of Athens, Lofos Nimfon, Thissio, Athens, 11810, Greece
  • 3Department of Environmental Technologists, Technological Education Institute (TEI) of the Ionian islands, Zakynthos, 29100, Greece
  • 4Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing, National Observatory of Athens, Metaxa and Vasileos Pavlou, Penteli, Athens, 15236, Greece
  • 5Department of Electronics Engineering, Technological Education Institute (TEI) of Athens, Ag. Spyridonos, Aigaleo, Athens, 12210, Greece
  • 6Department of Physics, Section of Solid State Physics, University of Athens, Panepistimiopolis, 15784, Zografos, Athens, Greece

Abstract. The preparation process of two recent earthquakes (EQs) that occurred in Cephalonia (Kefalonia), Greece, ((38.22° N, 20.53° E), 26 January 2014, Mw = 6.0, depth  ∼  20 km) and ((38.25° N, 20.39° E), 3 February 2014, Mw = 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.

Short summary
Based on the methods of critical fluctuations and natural time, we have shown that the fracture-induced MHz electromagnetic emissions recorded by two stations in our network prior to two recent significant earthquakes that occurred in Cephalonia present criticality characteristics, implying that they emerge from a system in critical state.