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  • Open Access English
    Authors: 
    G. Chouliaras; Nikolaos S. Melis; George Drakatos; Konstantinos Makropoulos;
    Publisher: Copernicus Publications
    Project: EC | EPOS (262229)

    International audience; The seismological network of the National Observatory of Athens (NOA) has systematically improved the detection capabilities in the Southeastern Mediterranean, by the continuous expansion and upgrading of the seismic stations and improvements in the operating and reporting procedures. As aresult of these improvements, the number of detected events of smaller magnitudes has increased and today a homogeneous magnitude is determined and disseminated towards the scientific community.

  • Open Access English
    Authors: 
    Louis De Barros; Frédéric Cappa; Yves Guglielmi; Laure Duboeuf; Jean-Robert Grasso;
    Publisher: HAL CCSD
    Countries: United States, France
    Project: EC | EPOS IP (676564), ANR | HYDROSEIS (ANR-13-JS06-0004), EC | SERA (730900)

    International audience; The ability to predict the magnitude of an earthquake caused by deep fluid injections is an important factor for assessing the safety of the reservoir storage and the seismic hazard. Here, we propose a new approach to evaluate the seismic energy released during fluid injection by integrating injection parameters, induced aseismic deformation, and the distance of earthquake sources from injection. We use data from ten injection experiments performed at a decameter scale into fault zones in limestone and shale formations. We observe that the seismic energy and the hydraulic energy similarly depend on the injected fluid volume (V), as they both scale as V3/2. They show, however, a large discrepancy, partly related to a large aseismic deformation. Therefore, to accurately predict the released seismic energy, aseismic deformation should be considered in the budget through the residual deformation measured at the injection. Alternatively, the minimal hypocentral distance from injection points and the critical fluid pressure for fault reactivation can be used for a better prediction of the seismic moment in the total compilation of earthquakes observed during these experiments. Complementary to the prediction based only on the injected fluid volume, our approach opens the possibility of using alternative monitoring parameters to improve traffic-light protocols for induced earthquakes and the regulation of operational injection activities.

  • English
    Authors: 
    Déprez, Aline; Socquet, Anne; Cotte, Nathalie; Walpersdorf, Andrea;
    Publisher: HAL CCSD
    Country: France
    Project: EC | EPOS (262229)

    International audience; In the framework of EPOS (EPOS - European Plate Observing System) project implementation phase, an analysis center is hosted in France at Université Grenoble Alpes – CNRS.Within the work package WP10, GNSS data and product, UGA-CNRS is responsible for providing products (position time series and velocity field) generated by a processing using double difference method (via GAMIT/GLOBK software). For this purpose, we developed strategies to take up the up-scaling challenge and generate from a big data set the usual GNSS products. For computational efficiency, the massive data set was split into sub-networks and the GAMIT software launched for each sub-network independently, following the same approach than the one presented in the framework of the PBO project.The informatics resources at our disposal are composed of a management tool for batch processing on computing environments (CiGri) and an open source data management software (IRODS), installed on the high performance computer available at UGA (CIMENT). Concerning the velocity field computation, we used MIDAS software. A few different tests were performed in order to check the reliability of our solution and to determine the best way to proceed.We also take advantage of the human and computational resources available in order to include in our solution some no-EPOS stations and generate:- An exhaustive solution in France, including stations from Rénag, RGP and Orpheon. Such dense solution was never performed before using DD method. - A solution in Greece including data from the SMARTNET network.Our solution includes more than 1500 stations constituting a widespread pan-European network, over an 18-years time span [2000-2017].; Dans le cadre de la phase de mise en œuvre du projet EPOS (EPOS - European Plate Observing System), un centre d'analyse est hébergé en France à l'Université Grenoble Alpes - CNRS.Dans le cadre du work package WP10, données GNSS et produit, UGA-CNRS est responsable de la fourniture des produits (séries temporelles de position et champ de vitesse) générés par un traitement utilisant la méthode des doubles différences (via le logiciel GAMIT/GLOBK). Pour ce faire, nous avons développé des stratégies pour relever le défi de la mise à l'échelle et générer à partir d'un grand ensemble de données les produits GNSS habituels. Par souci d'efficacité informatique, l'énorme ensemble de données a été divisé en sous-réseaux et le logiciel GAMIT a été lancé indépendamment pour chaque sous-réseau, suivant la même approche que celle présentée dans le cadre du projet PBO.Les moyens informatiques à notre disposition sont composés d'un outil de gestion des traitements batch sur environnements informatiques (CiGri) et d'un logiciel de gestion de données open source (IRODS), installés sur l'ordinateur haute performance disponible chez UGA (CIMENT). En ce qui concerne le calcul du champ de vitesse, nous avons utilisé le logiciel MIDAS. Quelques tests différents ont été effectués afin de vérifier la fiabilité de notre solution et de déterminer la meilleure façon de procéder.Nous profitons également des ressources humaines et informatiques disponibles afin d'inclure dans notre solution des stations sans EPOS et de générer :- Une solution exhaustive en France, incluant les stations de Rénag, RGP et Orphéon. Une telle solution dense n'a jamais été réalisée avant l'utilisation de la méthode DD. - Une solution en Grèce incluant les données du réseau SMARTNET.Notre solution comprend plus de 1500 stations constituant un réseau paneuropéen étendu, sur une période de 18 ans (2000-2017).

  • Open Access English
    Authors: 
    Walpersdorf, A.; Pinget, L.; Vernant, P.; Sue, C.; Deprez, A.; Baize, Stéphane; Bascou, Pascale; Baudin, Sandrine; Bock, Olivier; Briole, Pierre; +45 more
    Publisher: HAL CCSD
    Country: France
    Project: EC | EPOS IP (676564), ANR | RESIF-CORE (ANR-11-EQPX-0040)

    International audience; The availability of GPS survey data spanning 22 years, along with several independent velocity solutions including up to 16 years of permanent GPS data, presents a unique opportunity to search for persistent (and thus reliable) deformation patterns in the Western Alps, which in turn allow a reinterpretation of the active tectonics of this region. While GPS velocities are still too uncertain to be interpreted on an individual basis, the analysis of range-perpendicular GPS velocity profiles clearly highlights zones of extension in the center of the belt (15.3 to 3.1 nanostrain/year from north to south), with shortening in the forelands. The contrasting geodetic deformation pattern is coherent with earthquake focal mechanisms and related strain/stress patterns over the entire Western Alps. The GPS results finally provide a reliable and robust quantification of the regional strain rates. The observed vertical motions of 2.0 to 0.5 mm/year of uplift from north to south in the core of the Western Alps is interpreted to result from buoyancy forces related to postglacial rebound, erosional unloading, and/or viscosity anomalies in the crustal and lithospheric root. Spatial decorrelation between vertical and horizontal (seismicity related) deformation calls for a combination of processes to explain the complex present-day dynamics of the Western Alps.

  • Open Access English
    Authors: 
    Beata Orlecka-Sikora; Stanislaw Lasocki; J. Kocot; Tomasz Szepieniec; Jean Robert Grasso; Alexander Garcia-Aristizabal; Marc Schaming; Pawel Urban; G.M. Jones; I. G. Stimpson; +22 more
    Publisher: HAL CCSD
    Countries: United Kingdom, France, France, Germany, Finland, United Kingdom, Germany
    Project: EC | EPOS IP (676564), EC | SERA (730900), EC | EPOS IP (676564), EC | SERA (730900)

    AbstractMining, water-reservoir impoundment, underground gas storage, geothermal energy exploitation and hydrocarbon extraction have the potential to cause rock deformation and earthquakes, which may be hazardous for people, infrastructure and the environment. Restricted access to data constitutes a barrier to assessing and mitigating the associated hazards. Thematic Core Service Anthropogenic Hazards (TCS AH) of the European Plate Observing System (EPOS) provides a novel e-research infrastructure. The core of this infrastructure, the IS-EPOS Platform (tcs.ah-epos.eu) connected to international data storage nodes offers open access to large grouped datasets (here termed episodes), comprising geoscientific and associated data from industrial activity along with a large set of embedded applications for their efficient data processing, analysis and visualization. The novel team-working features of the IS-EPOS Platform facilitate collaborative and interdisciplinary scientific research, public understanding of science, citizen science applications, knowledge dissemination, data-informed policy-making and the teaching of anthropogenic hazards related to georesource exploitation. TCS AH is one of 10 thematic core services forming EPOS, a solid earth science European Research Infrastructure Consortium (ERIC) (www.epos-ip.org).

  • Open Access English
    Authors: 
    Andreas Fichtner; Dirk Philip van Herwaarden; Michael Afanasiev; Saulė Simutė; Lion Krischer; Yeşim Çubuk-Sabuncu; Tuncay Taymaz; Lorenzo Colli; Erdinc Saygin; Antonio Villaseñor; +4 more
    Countries: Switzerland, Netherlands, Netherlands, Spain, Spain, France, Switzerland
    Project: EC | EPOS IP (676564), EC | CSEM (714069), EC | EPOS IP (676564), EC | CSEM (714069)

    We present a general concept for evolutionary, collaborative, multiscale inversion of geophysical data, specifically applied to the construction of a first-generation Collaborative Seismic Earth Model. This is intended to address the limited resources of individual researchers and the often limited use of previously accumulated knowledge. Model evolution rests on a Bayesian updating scheme, simplified into a deterministic method that honors today's computational restrictions. The scheme is able to harness distributed human and computing power. It furthermore handles conflicting updates, as well as variable parameterizations of different model refinements or different inversion techniques. The first-generation Collaborative Seismic Earth Model comprises 12 refinements from full seismic waveform inversion, ranging from regional crustal- to continental-scale models. A global full-waveform inversion ensures that regional refinements translate into whole-Earth structure. ©2018. American Geophysical Union. All Rights Reserved. This work was supported by the PASC project GeoScale, the CSCS computing time grant ch1, the European Research Council (ERC) under the EU’s Horizon 2020 programme (grant 714069), Istanbul Technical University, the National Science Council of Turkey, the A. v. Humboldt Foundation, and the EU-COST Action ES1401-TIDES-STSM. Andreas Fichtner et. al. Peer reviewed

  • Open Access English
    Authors: 
    Sébastien Chevrot; Matthieu Sylvander; Jordi Diaz; Roland Martin; Frédéric Mouthereau; Gianreto Manatschal; Emmanuel Masini; Sylvain Calassou; Frank Grimaud; Hélène Pauchet; +1 more
    Publisher: Nature Publishing Group
    Countries: Spain, France, Spain
    Project: EC | EPOS IP (676564), EC | EPOS IP (676564)

    We exploit the data from five seismic transects deployed across the Pyrenees to characterize the deep architecture of this collisional orogen. We map the main seismic interfaces beneath each transect by depth migration of P-to-S converted phases. The migrated sections, combined with the results of recent tomographic studies and with maps of Bouguer and isostatic anomalies, provide a coherent crustal-scale picture of the belt. In the Western Pyrenees, beneath the North Pyrenean Zone, a continuous band of high density/velocity material is found at a very shallow level (~10 km) beneath the Mauleon basin and near Saint-Gaudens. In the Western Pyrenees, we also find evidence for northward continental subduction of Iberian crust, down to 50–70 km depth. In the Eastern Pyrenees, these main structural features are not observed. The boundary between these two domains is near longitude 1.3 °E, where geological field studies document a major change in the structure of the Cretaceous rift system, and possibly a shift of its polarity, suggesting that the deep orogenic architecture of the Pyrenees is largely controlled by structural inheritance. The PYROPE (Pyrenean Observational Portable Experiment) project was supported by the Agence Nationale de la Recherche (ANR) Blanc Programme (project PYROPE, ANR-09- BLAN-0229). We also acknowledge SISMOB, the French seismic mobile pool (a component of the RESIF consortium - http://seismology.resif.fr), for providing us with the seismological instrumentation for the temporary deployments. Field work has been also partially funded by the Spanish Ministry of Economy and Competitiveness through Project MISTERIOS (CGL2013-48601-C2-2-R). Peer reviewed

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