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Recent crustal deformation and strain accumulation in the Marmara sea region, NW Anatolia, inferred from GPS measurements / Christian Straub (1996)

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Titre :	Recent crustal deformation and strain accumulation in the Marmara sea region, NW Anatolia, inferred from GPS measurements
Type de document :	Thèse/HDR
Auteurs :	Christian Straub, Auteur
Editeur :	Zurich : Institut für Geodäsie und Photogrammetrie IGP - ETH
Année de publication :	1996
Collection :	IGP Mitteilungen, ISSN 0252-9335 num. 058
Importance :	150 p.
Format :	21 x 30 cm
ISBN/ISSN/EAN :	978-3-906513-82-9
Note générale :	Bibliographie
Langues :	Anglais (eng)
Descripteur :	[Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] analyse comparative [Termes IGN] campagne GPS [Termes IGN] déformation de la croute terrestre [Termes IGN] données GPS [Termes IGN] Marmara, mer de [Termes IGN] positionnement par GPS [Termes IGN] risque naturel [Termes IGN] séisme
Index. décimale :	30.82 Applications géophysiques de géodésie spatiale
Résumé :	(auteur) This work analyzes recent crustal deformation in the Marmara Sea region, NW Anatolia, based on data derived from repeated GPS measurements. It is the geodetic part of the MARMARA poly-project of the Swiss Federal Institute of Technology (ETHZ). The overall goal of the Marmara poly-project is to examine the active tectonics and their interaction with groundwater circulation, heat flow and seismicity in northwestern Anatolia. In 1990, the Geodesy and Geodynamics Lab. (GGL) of the ETHZ established 52 GPS sites at the western end of the single strand North Anatolian Fault Zone (NAFZ) and its splaying into a complex fault system. This complexity is caused by the transition from the east-west oriented motion of the Anatolian block to the extensional regime of the Aegean Sea directing north-south. The GPS sites were occupied during three major GPS campaigns in 1990, 1992, and 1994. The GPS data were analyzed using the Bernese GPS Software. As a result of the combination of these campaigns a detailed velocity field of the transition zone between the westward motion of Anatolia and the extending Aegean Sea was obtained. The average rate of motion of Anatolia relative to Eurasia is 20 mm/a in a W direction. West of longitude 27.5°, the average direction of motion turns from W to WSW. From north to south, a gradual rate increase from 0 to 20 mm/a was found. Comparisons with deformation rates derived from the summation of seismic moment tensors suggest that less than 60% of the GPS inferred rates are released by earthquakes. The deformation rates are evaluated by means of strain and stress analysis, by using the method of collocation, examination of residuals relative to rigid Eulerian rotations, as well as a Finite Element model of the Marmara Sea region. Most deformation occurs along the northern strand of the NAFZ that runs from Mudurnu through the Gulf of izmit, passing the Marmara Sea, re-enters the Eurasian mainland and continuing to the Gulf of Saros. The Yalova peninsula endures considerable deformation as well. No significant deformation was found on the Biga peninsula. Thus, the western part of the middle strand that crosses the Biga peninsula is either inactive or locked. The Gulf of Edremit and the areas south of it are occupied by extensional processes in NNE-SSW direction (max. extension: 0.3 ppm/a [= u.strain/a]). The average shear-strain rate in the Marmara Sea region is 0.1 ppm/a (maximum shear: 0.3 ppm/a). The highest annual accumulation of density of strain energy (4 mJ/m3) and maximum shear stress (16 kN/m2) is located along the northern strand. The projection of the strain on the main fault allows us to determine the kind and amount of faulting that can be expected at individual fault lines. The dextral strike along the northern strand reaches 0.1-0.3 ppm/a. The results obtained from repeated GPS measurements compare well with the pattern of horizontal direction of major extension derived from seismotectonic and neotectonic data. In the East, the major horizontal extension directs NE-SW. Further to the west it gradually changes to almost N-S. Comparisons with rigid pole rotations for the Eastern Mediterranean, postulated by other authors, show that the Marmara region cannot be regarded as part of a rigid Anatolian block. The analysis of residuals to a rigid pole rotation of the Anatolian sites of the MARMARA GPS network (33.9°N, 29.8°E, CD=1.36°/Ma) depicts the location and size of the area of the main deformation. Cross-sectors radial to the best fitting pole reveal a detailed pattern of increase of deformation rates over the different fault lines. The deformation zones in the eastern and western part is narrow (=45 km). The zone for the middle sector undergoes a more distributed deformation (up to 100 km). The investigation of the radial residuals illustrates the overall extension of the Marmara region directing NE-SW. Finite Element calculations (2D, elasto-static) confirm the findings of the strain and stress analysis. Furthermore, they suggest that the known neotectonic fault geometry is capable of absorbing a considerable accumulation of distortion. However, the Finite Element model also gives indications for additional fault structures at the western end of the Marmara Sea and in Thrace, north and south of the northern strand striking subparallel to it. Finally, the strain field of the Eastern Mediterranean region is derived from GPS measurements spanning the whole region. The deformation pattern confirm the strong dextral motion along the NAFZ (0.2 ppm/a) as well as the extensional regimes of Western Anatolia and the Aegean Sea. Residuals from a rotation for the Eastern Mediterranean reveal that the Anatolian/Aegean region does not behave like a single rigid plate. The rates along the NAFZ show that there is a zone with a width of up to 100 km that endures strong internal deformation. The southern Aegean, Western, and Southwestern Greece do not fit to a simple rigid polar rotation at all.
Numéro de notice :	68913
Affiliation des auteurs :	non IGN
Thématique :	POSITIONNEMENT
Nature :	Thèse étrangère
DOI :	10.3929/ethz-a-001624667
En ligne :	http://dx.doi.org/10.3929/ethz-a-001624667
Format de la ressource électronique :	URL
Permalink :	https://documentation.ensg.eu/index.php?lvl=notice_display&id=64059

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Code-barres	Cote	Support	Localisation	Section	Disponibilité
68913-01	30.82	Livre	Centre de documentation	Géodésie	Disponible

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