Statistical significance of the precursory minima of the order parameter fluctuations of seismicity by modern methods of Statistical Physics

<p>An order parameter for seismicity was introduced in the frame of natural time analysis [1].  Recent studies of the fluctuations of this order parameter revealed the existence of minima preceding major earthquakes [2-7]. Here, we review the statistical significance of these minima by using recent methods of Statistical Physics, such as receiver operating characteristics [8] and event coincidence analysis [9,10]. These methods are also applied to the investigation [11] of the statistical significance of Seismic Electric Signals [12].</p><p>References</p><ol><li>Varotsos, P.A.; Sarlis, N.V.; Skordas, E.S. Natural Time Analysis: The new view of time. Precursory Seismic Electric Signals, Earthquakes and other Complex Time-Series; Springer-Verlag: Berlin Heidelberg, 2011.</li> <li>Sarlis, N.V.; Skordas, E.S.; Varotsos, P.A.; Nagao, T.; Kamogawa, M.; Tanaka, H.; Uyeda, S. Minimum of the order parameter fluctuations of seismicity before major earthquakes in Japan, Proc. Natl. Acad. Sci. USA 110 (2013) 13734–13738, dx.doi.org/10.1073/pnas.1312740110.</li> <li>Varotsos, P.A.; Sarlis, N.V.; Skordas, E.S. Study of the temporal correlations in the magnitude time series before major earthquakes in Japan. J. Geophys. Res.: Space Physics 119 (2014) 9192–9206, dx.doi.org/10.1002/2014JA020580.</li> <li>Sarlis, N.V.; Christopoulos, S.R.G.; Skordas, E.S. Minima of the fluctuations of the order parameter of global seismicity. Chaos 25 (2015) 063110, dx.doi.org/10.1063/1.4922300.</li> <li>Sarlis, N.V.; Skordas, E.S.; Christopoulos, S.-R.G.; Varotsos, P.A. Statistical significance of minimum of the order parameter fluctuations of seismicity before major earthquakes in Japan, Pure Appl. Geophys. 173 (2016) 165–172, dx.doi.org/10.1007/s00024-014-0930-8.</li> <li>Sarlis, N.V.; Skordas, E.S.; Mintzelas, A.; Papadopoulou, K.A. Micro-scale, mid-scale, and macro-scale in global seismicity identified by empirical mode decomposition and their multifractal characteristics. Scientific Reports 8 (2018) 9206, dx.doi.org/10.1038/s41598-018-27567-y.</li> <li>Mintzelas, A.; Sarlis, N. Minima of the fluctuations of the order parameter of seismicity and earthquake networks based on similar activity patterns. Physica A 527 (2019) 121293, dx.doi.org/10.1016/j.physa.2019.121293.</li> <li>Fawcett, T., An introduction to ROC analysis, Pattern Recognit. Lett. 27 (2006) 861–874, dx.doi.org/10.1016/j.patrec.2005.10.010.</li> <li>Donges, J.; Schleussner, C.F.; Siegmund, J.; Donner, R. Event coincidence analysis for quantifying statistical interrelationships between event time series. The European Physical Journal Special Topics 225 (2016) 471–487, dx.doi.org/10.1140/epjst/e2015-50233-y.</li> <li>Siegmund, J.F.; Siegmund, N.; Donner, R.V. CoinCalc - A new R package for quantifying simultaneities of event series. Computers & Geosciences 98 (2017) 64-72, dx.doi.org/10.1016/j.cageo.2016.10.004.</li> <li>Sarlis, N.V. Statistical Significance of Earth’s Electric and Magnetic Field Variations Preceding Earthquakes in Greece and Japan Revisited. Entropy 20 (2018) 561, dx.doi.org/10.3390/e20080561.</li> <li>Varotsos, P.; Lazaridou, M. Latest aspects of earthquake prediction in Greece based on seismic electric signals, Tectonophysics 188 (1991) 321–347, dx.doi.org/10.1016/0040-1951(91)90462-2.</li> </ol>

Natural Time Analysis: Results Related to Two Earthquakes in Greece during 2019

The following two earthquakes occurred in Greece during 2019: First, a Mw5.4 earthquake close to Preveza city in Western Greece on 5 February and a Mw5.3 earthquake 50 km East of Patras on 30 March. Here, we present the natural time analysis of the Seismic Electric Signals (SES) activities that have been recorded before these two earthquakes. In addition, we explain how the occurrence times of these two earthquakes can be identified by analyzing in natural time the seismicity subsequent to the SES activities.

Features of criticality in precursory seismic electric signals and earthquakes in Greece

Very recently the recordings of precursory seismic electric signals (SESsf) in the island of Kozu-shima, Japan, have been reported, and their interrelation with subsequent earthquakes was shown to be beyond chance. Almost simultaneously, the recording of SES activity in northern Greece was also reported, which was followed by a magnitude 5.7 earthquake in northern Greece. These facts strengthen the aspects on the precursory nature of SESs and also enable the updating of a previously found power law relation between the earthquake stress drop and the lead time of SESs. They led to an exponent of 0.330, which falls in the range of critical exponents for fracture. The stability of this exponent, which results from a large amount of data during the last 30 yr, is remarkable and may thus confirm features of criticality in the pre-seismic region after the SES emission. The underlying physics are also discussed.