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Analysis of long-term GPS observations in Greece (1993-2009) and geodynamic implications for the Eastern Mediterranean / Michael D. Müller (2011)  

Public Titre : Analysis of long-term GPS observations in Greece (1993-2009) and geodynamic implications for the Eastern Mediterranean Type de document : Rapport Auteurs : Michael D. Müller, Auteur Editeur : Zurich : Schweizerischen Geodatischen Kommission / Commission Géodésique Suisse Année de publication : 2011 Collection : Geodätisch-Geophysikalische Arbeiten in der Schweiz, ISSN 0257-1722 num. 82 Importance : 186 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-908440-28-4 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] Athènes [Termes IGN] champ de vitesse [Termes IGN] collocation par moindres carrés [Termes IGN] Egée, mer [Termes IGN] Grèce [Termes IGN] méthode des éléments finis [Termes IGN] Péloponnèse [Termes IGN] séisme [Termes IGN] vitesse Index. décimale : 30.82 Applications géophysiques de géodésie spatiale Résumé : (Auteur) The Global Positioning System (GPS) is used to determine rates of crustal motion in the Hellenic plate boundary zone since the late eighties. The zone comprises Greece and its adjacent regions. It is characterized by the interaction of the Eurasian, Anatolian and Nubian plates moving relative to each other. Tectonic processes associated with this motion cause the highest seismic activity of Europe. Nine earthquakes with magnitude six or higher occurred within this region in the period 2006 to 2011. International efforts are being made to achieve a better understanding of the origin and characteristics of ongoing seismotectonic processes. The ETH Zurich has taken active part in these efforts. Results achieved so far provide valuable boundary conditions for geodynamic modeling. In close collaboration with other institutes an extensive GPS network has been established and periodically remeasured. The network consists of campaign-type and continuous GPS sites. The corresponding data record has been significantly extended in the course of the thesis. A 16 year record of GPS data (19932009) is available now for Greece. In its first part the thesis deals with the evaluation of the data record. The strategy of GPS analysis was enhanced compared to proceeding projects by applying recent GPS processing models and improving postprocessing procedures. The concept of including data of numerous IGS and EUREF sites located in Europe, North Africa and the Middle East was continued. This allowed for a precise alignment of the GPS network to a global reference frame (ITRF2005), the reduction of processing induced systematic signals and the determination of a pole of rotation for the Eurasian plate. An improved kinematic field was derived which was analyzed in terms of slowly deforming regions by using a block model. The modeling provides several insights. For instance, northwestern Greece rotates clockwise (cw) and the region south of the North Aegean trough (NAT) rotates counterclockwise (ccw) relative to Eurasia. Both areas form blocks with small internal deformation. Moreover, they describe the western termination of the North Aegean trough. A large part of ongoing deformation is located in confined regions. The GPS derived deformation field provides information about ongoing tectonic processes. These include N-S extension between Northern Greece and the Gulf of Corinth and dextral shear strain in the North Aegean sea as well as along the Kefalonia fault zone in the Ionian sea. New results concerning ongoing deformation processes were achieved in the Southeast Aegean sea and in Northern Greece. Pronounced N-S extension (100 nstrain/yr) was determined across the Mygdonian graben. NNW-SSE extension amounting to 150 nstrain/yr was found between the islands of Kalymnos and Tilos in the SE Aegean sea. The NAT and the Kefalonia fault zone are among the most pronounced transform faults in the Hellenic plate boundary zone. Rates of closely located GPS sites were used for the estimation of the slip rates and locking depths of the structures. Four profiles across the NAT show a decrease of slip rates from the Ganos fault (23 mm/yr) towards the southwestern edge of the Sporades basin (<5 mm/yr). The geodetic results provide further evidence that the NAT forms the westward continuation of the North Anatolian fault zone commencing at the Saros basin. The decrease of slip rates west of the Chalkidiki peninsula is related to a different orientation of the NAT and to NNE-SSW extension in the Sporades basin. Finite element models were used to relate GPS rates to basic geodynamic models. The first model I focused at the analysis of the subduction rate near the central Hellenic trench. The results point to a largely uncoupled interface between the Nubian and Aegean plates. The second model quantifies the slip rates along the three major NE-SW to ENE-WSW trending transform faults in the North Aegean sea. Rates amounting to 21 mm/yr were derived for the NAT, 10 mm/yr for the Skyros- Edremit fault and 4 mm/yr for the Psara-Lesvos fault. Moreover, the model reveals additional deformation zones such as NNE-SSW extension in the Sporades basin. The derived GPS rates and the conducted analyses improve the current understanding of seismotectonic processes in Greece. The investigations also highlight remaining problems and bring forward new ideas which will ultimately be valuable for further analysis and assessment of natural hazard in Greece. Note de contenu : 1 Introduction 1.1 State of research 1.2 Goals 2 Geologic setting 2.1 Evolution of the central and eastern Mediterranean 2.2 Tectonic framework of Greece 3 GPS data evaluation 3.1 Description of relevant GPS networks 3.1.1 Campaign-type GPS network in Greece and southern Bulgaria 3.1.2 Continuous GPS networks in Greece 3.1.3 IGS and EUREF sites 3.2 Strategy of GPS data processing 3.3 Definition of the geodetic datum 3.4 Velocity estimation of CGPS sites 3.4.1 Introduction 3.4.2 Discontinuities in position time series 3.4.3 Removing outliers 3.4.4 Exclusion periods 3.4.5 Estimation of velocities and offsets 3.4.6 Reduction of apparent scale changes of the processed GPS network 3.4.7 Scaling of formal errors of velocities 3.5 Velocity estimation of campaign-type GPS sites 3.6 Factors affecting the velocity estimates 3.6.1 Tracking performance of GPS sites 3.6.2 Used orbits and earth orientation parameters 3.6.3 Campaign-type data of the years 1993 and 1994 3.7 Concluding remarks 4 Kinematic field in Greece (19932009) 4.1 Introduction 4.2 Euler vector and estimation of a pole of rotation for Eurasia (ITRF2005) 4.3 Kinematic block model for Greece 4.4 Kinematic field and modeling in the North Aegean domain 4.4.1 Kinematic field 4.4.2 Slip rates and locking depths along the North Aegean trough 4.5 Kinematics along the Hellenic trench system 4.5.1 Ionian islands, Western Greece and NW Peloponnesos 4.5.2 Southern Peloponnesos and South Aegean sea 4.6 Vertical motion in Greece 4.7 Concluding remarks 5 Strain rates derived by using the method of collocation 5.1 Least-squares collocation 5.2 Velocity and strain rate fields calculation implemented in the program 'strain' 5.3 Strain rates and differential rotations in Greece 5.4 Concluding remarks 6 Seismic signals in GPS time series 6.1 Introduction 6.2 Estimation of earthquake displacements 6.3 Analytical surface dislocation model 6.4 Earthquakes in the Aegean domain 6.4.1 1999 Ms 5.9 Athens earthquake 6.4.2 2001 Mw 6.4 Skyros earthquake 6.4.3 2008 Mw 6.4 Rhodes earthquake 6.5 Earthquakes in the Ionian sea 6.5.1 1997 Mw 6.6 Strofades earthquake 6.5.2 2003 Mw 6.2 Lefkada earthquake 6.5.3 2006 Zakynthos earthquake series 6.5.4 2008 Mw 6.4 NW Peloponnesos earthquake 6.5.5 Comparison of seismicity and interseismic strain rates 6.6 Concluding remarks 7 Finite element models 7.1 Finite element method 7.1.1 Basic theory 7.1.2 Displacement-based finite element analysis 7.2 Physical properties of a model lithosphere 7.2.1 Introductory notes 7.2.2 Elasticity 7.2.3 Brittle failure 7.2.4 Ductile deformation 7.2.5 Temperature in the continental lithosphere 7.3 Interaction between the overriding and the subducting plate at the central Hellenic trench 7.3.1 Geodetic constraints 7.3.2 Developed finite element model 7.4 3D finite element model of the North Aegean sea 7.4.1 Introduction 7.4.2 Model set up 7.4.3 Results 7.5 Concluding remarks 8 Conclusions Numéro de notice : 14311 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Rapport de recherche En ligne : https://www.sgc.ethz.ch/sgc-volumes/sgk-82.pdf Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=62654

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14311-01	30.82	Livre	Centre de documentation	Géodésie	Disponible