Repeating earthquakes in western Corinth Gulf (Greece): implications for aseismic slip near locked faults

International audienceAn extensive search for repeating earthquakes was performed in the western Corinth Gulf by applying waveform cross correlation on 22,000 earthquakes that occurred in 2008–2014. Event pairs with high correlation coefficient (CC ≥ 0.95) recorded by two or more stations are classified as multiplets of repeating events. The highly similar event pairs have typically interevent distances less than a quarter wavelength (∼150 m for a dominant frequency of 10 Hz) and are used to estimate the accuracy of the relocated catalog. A detailed analysis of the spatiotemporal properties of the repeating sequences revealed two types of repeating events, namely, burst like and continuous type repeaters. Burst like repeaters are widespread in the entire study area, mostly associated with seismic excitations located at depths between 5 and 9 km, triggered either by fluid intrusion or stress transfer. Their duration is short with high values of coefficient of variation in recurrence intervals (COV > 1) and high slip rates. The continuous type repeaters, which last 1 to 7 years, with COV ∼ 1 and slip rates almost 0.26 cm/yr, form a very narrow shallow north dipping seismic zone at 10 km depth along the Psathopyrgos and Aigion faults. That kind of activity provides strong evidence for aseismic slip in the western Corinth Gulf and defines the boundaries between brittle-ductile transition in the area

Realism and Objectivism in Quantum Mechanics

The present study attempts to provide a consistent and coherent account of what the world could be like, given the conceptual framework and results of contemporary quantum theory. It is suggested that standard quantum mechanics can, and indeed should, be understood as a realist theory within its domain of application. It is pointed out, however, that a viable realist interpretation of quantum theory requires the abandonment or radical revision of the classical conception of physical reality and its traditional philosophical presuppositions. It is argued, in this direction, that the conceptualization of the nature of reality, as arising out of our most basic physical theory, calls for a kind of contextual realism. Within the domain of quantum mechanics, knowledge of 'reality in itself', 'the real such as it truly is' independent of the way it is contextualized, is impossible in principle. In this connection, the meaning of objectivity in quantum mechanics is analyzed, whilst the important question concerning the nature of quantum objects is explored.Comment: 20 pages. arXiv admin note: substantial text overlap with arXiv:0811.3696, arXiv:quant-ph/0502099, arXiv:0904.2702, arXiv:0904.2859, arXiv:0905.013

Spatio-temporal earthquake clustering in the Western Corinth Gulf

Η ευρύτερη περιοχή του Κορινθιακού κόλπου λόγω της πολύπλοκης καιενδιαφέρουσας σεισμοτεκτονικής συμπεριφοράς που παρουσιάζει έχει αποτελέσει το αντικείμενο έρευνας πολλών μελετών (γεωλογικών, σεισμολογικών, γαιωδαιτικών κ.λ.π.). Τα τελευταία πέντε τουλάχιστον χρόνια έχει παρατηρηθεί μία έντονη σεισμική δραστηριότητα η οποία καλύπτει την περιοχή δυτικά του Αιγίου, το στενό Ρίου-Αντιρρίου μέχρι την πόλη της Πάτρας. Τα δεδομένα της παρούσας εργασίας καλύπτουντη χρονική περίοδο 2010-2011 κατά την οποία καταγράφηκε έντονη σεισμική δρστηριότητα με ισχυρούς σεισμούς (μέχρι Μ=5.5) και χωροχρονικές συγκεντρώσεις της σεισμικότητας. Οι καταγραφές των σεισμών από το Ενιαίο Ελληνικό Σεισμολογικό δίκτυο χρησιμοποιήθηκαν για τον ακριβή επαναπροσδιορισμό των εστιακώνπαραμέτρων των σεισμών με μέγεθος Μ≥1.5 χρησιμοποιώντας το πρόγραμμα HYPOINVERSE. Με βάση τα δεδομένα και τα αποτελέσματα από τον επαναπροσδιορισμό των εστιακών συντεταγμένων, η χωροχρονική κατανομή έδειξε ότι η σεισμικότητα συγκεντρώνεται σε κάποιες συστάδες σεισμών σε περιοχές που είναι πιθανό να συνδέονται και με ροή ρευστών λόγω της θέσης των σεισμών σε υποθαλάσσια περιοχή. Η παρούσα εργασία μελετά τη χωρική και χρονική κατανομήτης σεισμικότητας στο δυτικό τμήμα του Κορινθιακού κόλπου με σκοπό να ελεγχθεί τυχόν “μετανάστευση” της σεισμικότητας και σύνδεσή της με τις σεισμοτεκτονικά καθορισμένες περιοχές.Corinth Gulf has been studied, thoroughly using multidisciplinary approaches (geological, seismological, geodetic etc), which revealed its complicated tectonic behaviour. In the last five years or more, an intense continuous microseismic activity is observed in the westernmost part of the gulf covering the area from west of Aigio tothe area west of Rio Antirrio strait, near the city of Patras. Aiming to study in detail the properties of this microseismic manifestation, the recordings of the Hellenic Unified Seismological Network (HUSN) are used to accurately determine the focal coordinates of earthquakes with magnitudes M=1.5 or more. Relocation was performed using the HYPOINVERSE program, for all available data for the period 2010-2011 when earthquakes up to magnitude M=5.5 occurred. The space time plot of the epicentres shows that seismicity is not random in the area but formed distinctive clusters, indicating an E-W striking seismic zone whose patches are successively activated for certain periods. The present work deals with the investigation of spatio-temporal evolution of seismicity with the intention to examine the migration ofseismicity and multi-segment activation.

The 2006 Kythira (Greece), Mw6.7 slab-pull event: tectonic implications and the geometry of the hellenic wadati-benioff zone

A strong (Mw=6.7) intermediate depth earthquake occurred on 8 January 2006 (11:34 UTC) in southwestern Aegean Sea (Greece) causing limited damage to structures on the nearby islands of Kythira and Antikythira, as well as western Crete Island. The epicentral area belongs to the SW segment of the Hellenic Arc, which is known to be associated with the occurrence of large shallow and intermediate depth earthquakes, mainly due to the subduction of the Eastern Mediterranean oceanic lithosphere under the Aegean microplate. The main shock occurred on a dextral strike slip fault at a depth of 75 km, within the descending slab, as it is revealed by both, the spatial distribution of the accurately located aftershocks and its fault plane solution determined in the present study and implying a slab-pull event. The aftershock activity from 8 to 31 January 2006 is distributed in depths ranging from 55 to 75 km, and being comprised in an almost rectangular and vertical plane with a length equal to 28 km and a width of 20 km, which adequately defines the dimensions of the rupture area. The geometry of the Wadati-Benioff zone in this area, namely the southwestern part of the Hellenic Arc, is explored by an exhaustive analysis of all the available phase arrivals gathered from the International Seismological Centre, and the relocation of the earthquakes occurred since 1964 in the South-West Aegean region