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

Velocity models inferred from p-waves travel time curves in south Aegean

Με σκοπό τη δημιουργία μοντέλων ταχύτητας στην περιοχή του νοτίου Αιγαίου, χρησιμοποιούμε τις καταγραφές σεισμών κατά τη χρονική περίοδο από 1η Ιανουαρίου έως 3Ιη Αυγούστου 2005 από ένα νέο τηλεμετρικό δίκτυο που εγκαταστάθηκε και λειτουργεί στην περιοχή της Κρήτης. Τα μοντέλα ταχύτητας κατασκευάζονται από τις καμπύλες χρόνων διαδρομής των επιμηκών κυμάτων και χρησιμοποιούνται σε συνδυασμό με τις χρονικές διορθώσεις στο χρόνο άφιξης των σεισμικών κυμάτων σε κάθε σεισμολογικό σταθμό του δικτύου για τον ακριβή προσδιορισμό των εστιακών παραμέτρων των σεισμών που έχουν καταγραφεί στην περιοχή του νοτίου Αιγαίου με τη χρήση του προγράμματος HYPOINVERSE. Συνδυάζοντας όλες τις διαθέσιμες πληροφορίες από τη βιβλιογραφία και τα αποτελέσματα της παρούσας μελέτης προσδοκούμε να συμβάλουμε στην αποσαφήνιση του σεισμοτεκτονικού προτύπου της περιοχής καθώς και της γεωμετρίας της καταδυόμενης λιθόσφαιρας της ανατολικής Μεσογείου.The seismicity recorded during Ist January to 31st August 2005 from a new telemetry network installed and operating on the island of Crete, is used in an effort to obtain new velocity models for the area of south Aegean. The models are constructed from the P-waves travel time curves and are later used for the events relocation with the HYPOINVERSE algorithm and station delays calculation. Furthermore, results are discussed and compared with the ones derived from other significant previous works presented the last years. We anticipate by combining all the available information from the literature and the analysis of our data set to contribute to the seismotectonic modeling of the study area and to construct a most complete image of the geometry of the subducted plate

Improving the Price of Anarchy for Selfish Routing via Coordination Mechanisms

We reconsider the well-studied Selfish Routing game with affine latency functions. The Price of Anarchy for this class of games takes maximum value 4/3; this maximum is attained already for a simple network of two parallel links, known as Pigou's network. We improve upon the value 4/3 by means of Coordination Mechanisms. We increase the latency functions of the edges in the network, i.e., if $\ell_e(x)$ is the latency function of an edge $e$, we replace it by $\hat{\ell}_e(x)$ with $\ell_e(x) \le \hat{\ell}_e(x)$ for all $x$. Then an adversary fixes a demand rate as input. The engineered Price of Anarchy of the mechanism is defined as the worst-case ratio of the Nash social cost in the modified network over the optimal social cost in the original network. Formally, if \CM(r) denotes the cost of the worst Nash flow in the modified network for rate $r$ and \Copt(r) denotes the cost of the optimal flow in the original network for the same rate then [\ePoA = \max_{r \ge 0} \frac{\CM(r)}{\Copt(r)}.] We first exhibit a simple coordination mechanism that achieves for any network of parallel links an engineered Price of Anarchy strictly less than 4/3. For the case of two parallel links our basic mechanism gives 5/4 = 1.25. Then, for the case of two parallel links, we describe an optimal mechanism; its engineered Price of Anarchy lies between 1.191 and 1.192.Comment: 17 pages, 2 figures, preliminary version appeared at ESA 201

Malicious Bayesian Congestion Games

In this paper, we introduce malicious Bayesian congestion games as an extension to congestion games where players might act in a malicious way. In such a game each player has two types. Either the player is a rational player seeking to minimize her own delay, or - with a certain probability - the player is malicious in which case her only goal is to disturb the other players as much as possible. We show that such games do in general not possess a Bayesian Nash equilibrium in pure strategies (i.e. a pure Bayesian Nash equilibrium). Moreover, given a game, we show that it is NP-complete to decide whether it admits a pure Bayesian Nash equilibrium. This result even holds when resource latency functions are linear, each player is malicious with the same probability, and all strategy sets consist of singleton sets. For a slightly more restricted class of malicious Bayesian congestion games, we provide easy checkable properties that are necessary and sufficient for the existence of a pure Bayesian Nash equilibrium. In the second part of the paper we study the impact of the malicious types on the overall performance of the system (i.e. the social cost). To measure this impact, we use the Price of Malice. We provide (tight) bounds on the Price of Malice for an interesting class of malicious Bayesian congestion games. Moreover, we show that for certain congestion games the advent of malicious types can also be beneficial to the system in the sense that the social cost of the worst case equilibrium decreases. We provide a tight bound on the maximum factor by which this happens.Comment: 18 pages, submitted to WAOA'0

Structural identification of Egnatia Odos bridges based on ambient and earthquake induced vibrations

The dynamic characteristics of two representative R/C bridges on Egnatia Odos motorway in Greece are estimated based on low amplitude ambient and earthquake-induced vibrations. The present work outlines the instrumentation details, algorithms for computing modal characteristics (modal frequencies, damping ratios and modeshapes), modal-based finite element model updating methods for estimating structural parameters, and numerical results for the modal and structural dynamic characteristics of the two bridges based on ambient and earthquake induced vibrations. Transverse, bending and longitudinal modes are reliably identified and stiffness-related properties of the piers, deck and elastomeric bearings of the finite element models of the two bridges are estimated. Results provide qualitative and quantitative information on the dynamic behavior of the bridge systems and their components under low-amplitude vibrations. Modeling assumptions are discussed based on the differences in the characteristics identified from ambient and earthquake vibration measurements. The sources of the differences observed between the identified modal and structural characteristics of the bridges and those predicted by finite element models used for design are investigated and properly justified

Vitamin-V: Virtual Environment and Tool-boxing for Trustworthy Development of RISC-V based Cloud Services

Vitamin-V is a 2023-2025 Horizon Europe project that aims to develop a complete RISC-V open-source software stack for cloud services with comparable performance to the cloud-dominant x86 counterpart and a powerful virtual execution environment for software development, validation, verification, and test that considers the relevant RISC-V ISA extensions for cloud deployment

Measurement of χ c1 and χ c2 production with s√ = 7 TeV pp collisions at ATLAS

The prompt and non-prompt production cross-sections for the χ c1 and χ c2 charmonium states are measured in pp collisions at s√ = 7 TeV with the ATLAS detector at the LHC using 4.5 fb−1 of integrated luminosity. The χ c states are reconstructed through the radiative decay χ c → J/ψγ (with J/ψ → μ + μ −) where photons are reconstructed from γ → e + e − conversions. The production rate of the χ c2 state relative to the χ c1 state is measured for prompt and non-prompt χ c as a function of J/ψ transverse momentum. The prompt χ c cross-sections are combined with existing measurements of prompt J/ψ production to derive the fraction of prompt J/ψ produced in feed-down from χ c decays. The fractions of χ c1 and χ c2 produced in b-hadron decays are also measured