Brief Communication: The recent seismic activity in Central Greece in 2013 and its precursory electric signals in terms of criticality

E Dologlou

doi:10.5194/npg-21-149-2014

Abstract

Abstract. Here, we check the obedience of new data, derived from the Mw = 5.4 earthquake on 7 August 2013 in Central Greece, to a previously found power law relation by the author between the stress drop of an earthquake and the lead time of its precursory seismic electric signal (SES). An exponent value α =0.329 has been found which is in excellent agreement with previous ones reported in a series of articles by the author. This value falls in the range of critical exponents suggested by various models for fracture and is very close to a reported one which interconnects the amplitude of the SES and the magnitude of the impending earthquake. The stability of this exponent confirms the credibility of the above-mentioned power law and probably implies that real physical dynamic processes evolving to criticality are present in the pre-focal area when the SES is emitted.

Highlights

The concept that the preparation processes of large earthquakes can be better understood in terms of statistical physics of a critical phase transition culminating in a cataclysmic event, is widely adopted by many investigators (Andersen et al, 1997; Keilis-Borok, 1990; Rundle et al, 2000)
We focus on DC-ULF electric signals, termed seismic electric signals (SES), which are recognized as transient lowfrequency (≤ 1 Hz) variations of the Earth’s telluric field and have been found to precede large earthquakes in Greece and Japan (Varotsos and Alexopoulos, 1984a, b; Varotsos et al, 1993; Orihara et al, 2012)
The update of a previously found power law relation between the stress drop of an earthquake and the lead time of its associated SES, by inserting new data from the Mw = 5.4 earthquake on 7 August 2013 in Central Greece, led to an exponent value α = 0.329 which is in excellent agreement with the reported ones by the author

Summary

Introduction

The concept that the preparation processes of large earthquakes can be better understood in terms of statistical physics of a critical phase transition culminating in a cataclysmic event, is widely adopted by many investigators (Andersen et al, 1997; Keilis-Borok, 1990; Rundle et al, 2000).Fracture in heterogeneous materials, such as the highly fragmented Earth’s crust, could be viewed as a critical phenomenon and has been a field of active study in recent years (Lamaignère et al, 1996; Sornette and Sornette, 1990). We focus on DC-ULF electric signals, termed seismic electric signals (SES), which are recognized as transient lowfrequency (≤ 1 Hz) variations of the Earth’s telluric field and have been found to precede large earthquakes in Greece and Japan (Varotsos and Alexopoulos, 1984a, b; Varotsos et al, 1993; Orihara et al, 2012). They are emitted from the prefocal area when the tectonic stress reaches a critical value which signals the entrance of the region into a critical stage

Objectives

Discussion

Conclusion