Σκοπός της διπλωματικής αυτής είναι η μελέτη των φυσικών χαρακτηριστικών της σεισμογένεσης με μεθόδους μη- εκτατικής στατιστικής φυσικής, στην ΒΔ Περι-Ειρηνική ζώνη. Η εκτατική στατιστική των Boltzmann-Gibbs δεν μπορεί να εφαρμοστεί για συστήματα τα οποία βρίσκονται εκτός ισορροπίας και τα μέλη του αλληλεπιδρούν. Τέτοιο σύστημα αποτελεί και ο ενεργός τεκτονικός ιστός. Για αυτά τα συστήματα εισέρχεται η θεωρία της μη-εκτατικής στατιστικής φυσικής (NESP) η οποία αποτελεί μια γενίκευση της στατιστικής των Boltzmann-Gibbs. Αυτό που εξετάζεται, χρησιμοποιώντας το φορμαλισμό της NESP, είναι το αν η σεισμικότητα αποτελεί ένα τέτοιο σύστημα που βρίσκεται σε ισορροπία. Αν ναι, τότε θα αποτελεί μια σημειακή Poissonian διεργασία η οποία ακολουθεί τους κανόνες της θερμοδυναμικής Boltzmann-Gibbs,αν όχι, τότε θα ερμηνεύεται από τους κανόνες της μη-εκτατικής στατιστικής φυσικής. Ο κατάλογος που χρησιμοποιήθηκε για την μελέτη αυτή είναι ο ενοποιημένος σεισμικός κατάλογος της Japan Meteorological Agency (JMA) και αφορά το διάστημα 01/01/2002 μέχρι και τις 31/05/2016. Επιλέχθηκε ένα κατώφλι μεγέθους Μ3 και ο συνολικός αριθμός των δεδομένων είναι 103.696. Συγκεκριμένα αυτό που εξετάζεται είναι η ύπαρξη αλληλεπιδράσεων (συσχετίσεων μακριάς εμβέλειας) μελετώντας q-κατανομές για παραμέτρους α) Μεγέθους - Γενικευμένος Νόμος των Gutenberg-Richter, β) Χρόνου αναμονής - Interevent times - όπου αποτελεί τον χρόνο μεταξύ διαδοχικών γεγονότων, και, γ) Ενδιαμέσων αποστάσεων - Interevent Ditance- όπου αποτελούν τις αποστάσεις μεταξύ διαδοχικών γεγονότων. Επιπλέον υπολογίζονται b-values τα οποία παράγονται από τους εντροπικούς δείκτες, και συγκρίνονται με το b-value των Gutenberg-Richter για να διαπιστωθεί το αν η ανάλυση αυτή πλησιάζει τις πραγματικές τιμές.
(EL)
The Thesis examines the nature of seismogenetic systems along the north-western rim of the Circum-Pacific belt by searching for evidence of complexity and non-extensivity in the earthquake record. The objective is to determine whether earthquakes are generated by a self-excited Poisson process, in which case they obey Boltzmann-Gibbs thermodynamics, or by a Critical process, in which long-range interactions in non-equilibrium states are expected (correlation) and the thermodynamics deviate from the Boltzmann-Gibbs formalism. Emphasis is given to background seismicity since it is generally agreed that aftershock sequences comprise correlated sets. Because the study area features convergent plate boundaries that include both crustal (in the lithosphere), and sub-crustal (in the Wadati-Benioff zones) earthquakes, the analysis was carried out by roughly separating crustal and sub-crustal seismicity according to the depth of the Mohorovičić discontinuity, in an attempt inquire whether environmental conditions (e.g. temperature, pressure), or/and boundary conditions (free at the surface vs. fixed at depth), affect the dynamic expression and evolution of seismogenetic fault networks. The analysis uses the complete and homogeneous Unified Seismic Catalogue of Japan, obtained from The earthquake data used in the study span the time period 1/1/2002 – 31/5/2016 and was provided by the National Research Institute for Earth Science and Disaster Resilience, the Japan Meteorological Agency, Hokkaido University, Hirosaki University, Tohoku University, the University of Tokyo, Nagoya University, Kyoto University, Kochi University, Kyushu University, Kagoshima University, the National Institute of Advanced Industrial Science and Technology, the Geographical Survey Institute, Tokyo Metropolis, Shizuoka Prefecture, Hot Springs Research Institute of Kanagawa Prefecture, Yokohama City, and Japan Agency for Marine-Earth Science and Technology. The earthquake catalogue is available in the website of the National Research Institute for Earth Sciences and Disaster Prevention (NIED). The analysis examined multivariate cumulative frequency distributions of earthquake magnitude, interevent time and interevent distance in the context of Non-Extensive Statistical Physics, which is a generalization of extensive Boltzmann-Gibbs thermodynamics to non-equilibrating (non-extensive) systems. It follows that the results are obtained through a physics-based approach and not through any type of model-based (or model-driven) consideration, as usually is the case in earthquake statistical studies. The analysis was applied to different catalogue realizations in which aftershocks were either included, or had been removed by a stochastic declustering procedure. The results provide evidence that in the seismogenetic systems of the NW Circum-Pacific belt, background seismicity is complex sub-extensive of nature, although it exhibits significant differences between systems (plates): Complexity is certainly prominent in the Okhotsk and Pacific plates and definitely less evident in the Eurasia and Philippine plates where the systems appear to verge on randomness. In the Okhotsk and Pacific plates background seismicity exhibits strong long-range interaction as evident by the overall high correlation observed in highly declustered catalogues and, primarily, in the long-range interaction observed in earthquake groups separated by long interevent distances. The increase in the level of complexity after declustering can be neatly explained by the exposition of long range interactions after curtailing the effect of short-range interactions associated with aftershock sequences. It is also highly probable –but was not be investigated herein– that the elevated complexity (sub-extensivity) of the Okhotsk and Pacific seismicity is closely related to the 2011 M9 Tohoku mega-earthquake, whose preparation phase and aftermath has organized the seismogenetic systems over long ranges. Criticality is a likely explanation for the complexity observed in the background seismicity of Okhotsk and Pacific plates, inasmuch as power-laws and long-range interaction are its hallmarks. However, the question is still very far from having been answered as there may be alternative (albeit less likely) mechanisms by which complexity and power-laws and may arise. It is therefore clear that additional work is required before the complexity mechanism of background seismicity can be proposed with confidence.
(EN)
/aggregator-openarchives/portal/institutions/uoa
