Probabilistic seismic hazard assessment in Greece – Part 3: Deaggregation

The present third part of the study, concerning the evaluation of earthquake hazard in Greece in terms of various ground motion parameters, deals with the deaggregation of the obtained results The seismic hazard maps presented for peak ground acceleration and spectral acceleration at 0.2 s and 1.0 s, with 10% probability of exceedance in 50 years, were deaggregated in order to quantify the dominant scenario. There are three basic components of each dominant scenario: earthquake magnitude (<i>M</i>), source-to-site distance (<i>R</i>) and epsilon (ε). We present deaggregation maps of mean and mode values of M-R-ε triplet showing the contribution to hazard over a dense grid

An attempt to model the relationship between MMI attenuation and engineering ground-motion parameters using artificial neural networks and genetic algorithms

Complex application domains involve difficult pattern classification problems. This paper introduces a model of MMI attenuation and its dependence on engineering ground motion parameters based on artificial neural networks (ANNs) and genetic algorithms (GAs). The ultimate goal of this investigation is to evaluate the target-region applicability of ground-motion attenuation relations developed for a host region based on training an ANN using the seismic patterns of the host region. This ANN learning is based on supervised learning using existing data from past earthquakes. The combination of these two learning procedures (that is, GA and ANN) allows us to introduce a new method for pattern recognition in the context of seismological applications. The performance of this new GA-ANN regression method has been evaluated using a Greek seismological database with satisfactory results

Probabilistic seismic hazard assessment in Greece – Part 2: Acceleration response spectra and elastic input energy spectra

This second part of the study, deals with the evaluation of the earthquake hazard in Greece in terms of the response spectral acceleration and the elastic input energy equivalent velocity. Four sets of predictive equations were selected, two for each type of spectra. Probabilistic hazard maps were created by determining the seismic hazard at grid points covering the region of interest. The maps are presented for the dominant periods of 0.2 s and 1.0 s for each spectrum. Uniform hazard response spectra (UHRS) for six cities located in the regions of highest estimated hazard are also presented. The comparison with elastic design spectra proposed by the latest national building code, has shown that the UHRS values exceed the design values at almost all periods

Tsunami hazard assessment in the Ionian Sea due to potential tsunamogenic sources – results from numerical simulations

In spite of the fact that the great majority of seismic tsunami is generated in ocean domains, smaller basins like the Ionian Sea sometimes experience this phenomenon. In this investigation, we study the tsunami hazard associated with the Ionian Sea fault system. <br><br> A scenario-based method is used to provide an estimation of the tsunami hazard in this region for the first time. Realistic faulting parameters related to four probable seismic sources, with tsunami potential, are used to model expected coseismic deformation, which is translated directly to the water surface and used as an initial condition for the tsunami propagation. <br><br> We calculate tsunami propagation snapshots and mareograms for the four seismic sources in order to estimate the expected values of tsunami maximum amplitudes and arrival times at eleven tourist resorts along the Ionian shorelines. <br><br> The results indicate that, from the four examined sources, only one possesses a seismic threat causing wave amplitudes up to 4 m at some tourist resorts along the Ionian shoreline

Earthquake relocation for North-Western Greece using 3D crustal model; method comparison and seismotectonic interpretation.

Για  χρονική  περίοδο  ένδεκα  μηνών,  εγκαταστάθηκε  στην  Ήπειρο  ένα  πυκνό μικροσεισμικό δίκτυο. Κατά το διάστημα αυτό καταγράφηκαν συνολικά 1368 σεισμοί, τα  επίκεντρα  των  οποίων  προσδιορίστηκαν  με  χρήση  μονοδιάστατου  μοντέλου ταχυτήτων. Οι σεισμοί αυτοί χρησιμοποιήθηκαν στη συνέχεια για τον υπολογισμό 3Δ μοντέλου  ταχυτήτων.  Η  παρούσα  εργασία  παρουσιάζει  τα  αποτελέσματα  της περεταίρω επεξεργασίας των δεδομένων αυτών με εφαρμογή (α) της απλής μεθόδου προσδιορισμού  υποκέντρων  Hypo71  με  χρήση  1Δ  μοντέλου  ταχυτήτων,  (β)  της πιθανολογικής,  μη  γραμμικής  μεθόδου  προσδιορισμού  υποκέντρων  NonLinLoc  με χρήση  3Δ  μοντέλου  ταχυτήτων,  (γ)  της  μεθόδου  Double-Difference  με  χρήση  1Δ μοντέλου ταχυτήτων, για τον επαναπροσδιορισμό των υποκέντρων των σεισμών τα επίκεντρα των οποίων αρχικά είχαν εντοπιστεί με τη μέθοδο Hypo71, και (δ) την εφαρμογή της ίδιας μεθόδου επαναπροσδιορισμού υποκέντρων με χρήση 3Δ μοντέλου ταχυτήτων.  Η  εφαρμογή  των  διαφορετικών  μεθόδων  οδήγησε  σε  ελαφρώς διαφορετικές   κατανομές   υποκέντρων,   οι   οποίες   χρησιμοποιήθηκαν   για XLVII, No 3 - 1269λεπτομερέστερη  σκιαγράφηση  των  γραμμικών  δομών  της  περιοχής,  με  χρήση  της Μεθόδου  των  Τριών  Σημείων.  Οι  δομές  αυτές  συγκρίθηκαν  με  τους  μηχανισμούς γένεσης των σεισμών, οι οποίοι υπολογίστηκαν με τη μέθοδο πολικότητας και το 3Δ μοντέλο ταχυτήτων. Η υπολογισμένη με μεγάλη ακρίβεια θέση των υποκέντρων σε συνδυασμό με τους μηχανισμούς γένεσης παρείχαν σημαντικές πληροφορίες για το σεισμοτεκτονικό καθεστώς της Δυτικής ΕλλάδαA dense microseismic network was installed in Northwestern Greece for a period of eleven months. A total of 1368 events were recorded and located using a 1D model. These events were also used to derive a 3D velocity model for the area. This work presents results from further processing of the data using (a) simple location method of events in a 1D medium through Hypo71 standard procedure; (b) location via the probabilistic, non-linear earthquake location method in 3D medium; (c) relocation of the events using the Double - Difference method in 1D medium; and (d) the same relocation  procedure  invoking  3D  medium.  The  application  of  different  location methodologies results in slightly different locations, which are evaluated using as criterion the compactness of hypocenter distribution. The three point method was used in order to derive linear characteristics from the hypocenter distribution and the final results were compared against the focal mechanisms of the events as computed using the polarity method and the 3D velocity model. The combination of accurately computed hypocenters and focal mechanisms provides important information for the seismotectonics of Epiru

Probabilistic seismic hazard assessment in Greece – Part 1: Engineering ground motion parameters

Seismic hazard assessment represents a basic tool for rational planning and designing in seismic prone areas. In the present study, a probabilistic seismic hazard assessment in terms of peak ground acceleration, peak ground velocity, Arias intensity and cumulative absolute velocity computed with a 0.05 g acceleration threshold, has been carried out for Greece. The output of the hazard computation produced probabilistic hazard maps for all the above parameters estimated for a fixed return period of 475 years. From these maps the estimated values are reported for 52 Greek municipalities. Additionally, we have obtained a set of probabilistic maps of engineering significance: a probabilistic macroseismic intensity map, depicting the Modified Mercalli Intensity scale obtained from the estimated peak ground velocity and a probabilistic seismic-landslide map based on a simplified conversion of the estimated Arias intensity and peak ground acceleration into Newmark's displacement

The Patras earthquake (14 July 1993): relative roles of source, path and site effects

Abstract A damaging earthquake occurred on 14 July 1993 in Patras, Western Greece. The mainshock (local magnitude 5.1) was followed on the same day by two aftershocks of magnitudes 4.4 M L and 3.6 M L , respectively. The strong motion record of the mainshock is studied, based on the teleseismically determined seismic moment and focal mechanism. The Discrete Wavenumber (DW) and Empirical Green's Function (EGF) methods are used. The main conclusion is that the 1993 Patras mainshock had a complex S-wave group mainly due to structural (path and site) effect. However, some effects of the rupture stopping on the peak ground acceleration (0.2 g in the so-called S3 phase) cannot be ruled out. Two values of the source radius are suggested: R = 1.9 and 3.0 km. The strong motion record better agrees with R = 1.9 km. If the latter is true, the stress drop was of the order of 20 MPa, i.e., higher than often reported for comparable events in Western Greece. Regardless of the true source radius, the ratio of stress drops between the mainshock and aftershocks was about 1-2. The aftershock waveforms indicate significant lateral heterogeneities around Patras. Therefore, the ground-motion predictions of strong events in the area will remain highly non-unique until weak events from an immediate neighbourhood of the particular fault are recorded

A constraint-based approach to quality assurance in service choreographies.

Knowledge about the quality characteristics (QoS) of service com- positions is crucial for determining their usability and economic value. Ser- vice quality is usually regulated using Service Level Agreements (SLA). While end-to-end SLAs are well suited for request-reply interactions, more complex, decentralized, multiparticipant compositions (service choreographies) typ- ically involve multiple message exchanges between stateful parties and the corresponding SLAs thus encompass several cooperating parties with interde- pendent QoS. The usual approaches to determining QoS ranges structurally (which are by construction easily composable) are not applicable in this sce- nario. Additionally, the intervening SLAs may depend on the exchanged data. We present an approach to data-aware QoS assurance in choreographies through the automatic derivation of composable QoS models from partici- pant descriptions. Such models are based on a message typing system with size constraints and are derived using abstract interpretation. The models ob- tained have multiple uses including run-time prediction, adaptive participant selection, or design-time compliance checking. We also present an experimen- tal evaluation and discuss the benefits of the proposed approach

A Bayesian Argumentation Framework for Distributed Fault Diagnosis in Telecommunication Networks

Traditionally, fault diagnosis in telecommunication network management is carried out by humans who use software support systems. The phenomenal growth in telecommunication networks has nonetheless triggered the interest in more autonomous approaches, capable of coping with emergent challenges such as the need to diagnose faults' root causes under uncertainty in geographically-distributed environments, with restrictions on data privacy. In this paper, we present a framework for distributed fault diagnosis under uncertainty based on an argumentative framework for multi-agent systems. In our approach, agents collaborate to reach conclusions by arguing in unpredictable scenarios. The observations collected from the network are used to infer possible fault root causes using Bayesian networks as causal models for the diagnosis process. Hypotheses about those fault root causes are discussed by agents in an argumentative dialogue to achieve a reliable conclusion. During that dialogue, agents handle the uncertainty of the diagnosis process, taking care of keeping data privacy among them. The proposed approach is compared against existing alternatives using benchmark multi-domain datasets. Moreover, we include data collected from a previous fault diagnosis system running in a telecommunication network for one and a half years. Results show that the proposed approach is suitable for the motivational scenario