Πεδίο βαρύτητας ελλαδικού χώρου με έμφαση στην περιοχή της Σαντορίνης

Μελισσινός, Παρασκευάς; Melissinos, Paraskevas

dc.contributor.author	Μελισσινός, Παρασκευάς	el
dc.contributor.author	Melissinos, Paraskevas	en
dc.date.accessioned	2024-09-06T07:00:48Z
dc.date.available	2024-09-06T07:00:48Z
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/60150
dc.identifier.uri	http://dx.doi.org/10.26240/heal.ntua.27846
dc.rights	Αναφορά Δημιουργού-Μη Εμπορική Χρήση-Όχι Παράγωγα Έργα 3.0 Ελλάδα	*
dc.rights.uri	http://creativecommons.org/licenses/by-nc-nd/3.0/gr/	*
dc.subject	Βαρύτητα	el
dc.subject	Γεωειδές	el
dc.subject	Υψόμετρα	el
dc.subject	Σαντορίνη	el
dc.subject	Ηφαίστειο	el
dc.title	Πεδίο βαρύτητας ελλαδικού χώρου με έμφαση στην περιοχή της Σαντορίνης	el
dc.contributor.department	Ανώτερης Γεωδαισίας- Κέντρο Δορυφόρων Διονύσου	el
heal.type	doctoralThesis
heal.classification	Γεωδαισία	el
heal.classification	Γεωφυσική	el
heal.classification	Γεωπληροφορική	el
heal.language	el
heal.access	campus
heal.recordProvider	ntua	el
heal.publicationDate	2024-03-19
heal.abstract	This doctoral thesis focuses on describing a comprehensive process of utilizing gravity information for geodetic and geophysical purposes. The thesis aims to depict and explore the gravity field of the Greek territory, with an emphasis on the volcanic complex of Santorini. It comprises an introduction, seven chapters and bibliography. The first chapter briefly introduces and simplifies theoretical elements derived from the literature review. In the second chapter, there's a historical overview of acquiring gravimetric data by the Hellenic Military Geographical Service (HMGS) and the Na-tional Technical University of Athens (NTUA), followed by the description of the cor-rection of the national gravimetric network. The methodology for creating the new database of HMGS is also outlined, along with control algorithms. The third chapter approaches the gravity field of the Greek territory from a geodetic perspective. It begins with the determination of the geoid using all available data and its evaluation. The National Height System is then described, followed by the calculation of geodynamic parameters and useful conclusions about the country's height system. Additionally, a unified correction surface is constructed for the ho-mogenization of surfaces defining the National Height System. In the fourth chapter, a geophysical approach to the gravity field of Greece is con-ducted using the database. Various techniques from international literature are ap-plied to generate representations of different magnitudes of the gravity field. Con-clusions about various geodynamic and tectonic phenomena in the Greek region are drawn. The inversion of the gravity field is implemented to calculate a three-dimensional density model. The fifth chapter describes and provides appendixes for gravity measurements form-ing the microgravity network of Santorini, which can be used in future studies. The gravity field of the region is visualized, and valuable conclusions about the tectonics of the broader area are recorded. In the sixth chapter, a comparative evaluation and interpretation of spatiotemporal gravity variations in Santorini volcano are carried out for the first time. Models de-rived from these variations aid in interpreting and understanding internal volcanic processes. The seventh chapter summarizes the conclusions of all chapters and proposes fur-ther research directions and ways to improve the results. The main results of the thesis are: (a) The creation of a new homogenized database, consisting of 21,279 ground gravi-ty points, 2,450 raw measurements of marine gravity, 142,869 marine gravity grid nodes, and 50,373 grid nodes of neighboring countries' gravity. (b) Identification of the EIGEN 6C4 as the best Global Geodynamic Model(GGM) for the Greek region. Calculated Gravimetric Geoid improves the standard deviation of the GGM by 10%. The Gravimetric Geoid was adjusted to ground-based measure-ments, yielding a final model with a typical error of 6.2 cm. (c) Examination of the Greek Height System revealed its non-homogeneity, with over sixty different reference surfaces. The mean gravitational potential of this system was calculated at W0 = 62,636,860.64±0.03 m²/s². A unified correction surface was computed for the Greek region to homogenize orthometric heights. (d) Geophysical analysis indicated an average depth of mass concentration in the Greek region at approximately 29.9±1.9 km. The Airy model was found insufficient to compensate for all masses, leading to the inversion of Bouguer anomalies for a three-dimensional density model. Results showed an average Moho depth of about 28.75 km, upper crust thickness of 16.88 km, and sediment thickness up to 6-7 km. (e) The gravity field of the Santorini region displayed significant variations, revealing seven low-gravity basins. Profiles of residual and regional gravity anomalies were generated, identifying surface ruptures related to both shallow and deeper-seated faults. Geological boundaries of subsurface structures were determined, and small closed isoanomalous contours were associated with potential volcanic cones. (f) The analysis of temporal gravity variations in Santorini revealed two sources causing observed changes. The first corresponds to the Mogi point, estimated with geodetic methods during 2011-12, attributed to the influx of dense basaltic magma (~3.3x1011kg). The second source, located approximately 1350m below Nea Kameni, was linked to density changes arising from hydrothermal fluctuations, degassing, or vesicle collapse within stored magma. This process was found to be an ongoing phenomenon unaffected by the 2011-12 unrest, with the gravity increase likely con-tinuing at a diminishing rate.	en
heal.advisorName	Παραδείσης, Δημήτριος	el
heal.committeeMemberName	Νομικού, Παρασκευή	el
heal.committeeMemberName	Αναστασίου, Δημήτριος	el
heal.committeeMemberName	Βέργος, Γεώργιος	el
heal.committeeMemberName	Πάνου, Γεώργιος	el
heal.committeeMemberName	Λουπασάκης, Κωνσταντίνος	el
heal.committeeMemberName	Τσακίρη, Μαρία	el
heal.academicPublisher	Εθνικό Μετσόβιο Πολυτεχνείο. Σχολή Αγρονόμων και Τοπογράφων Μηχανικών. Τομέας Τοπογραφίας. Εργαστήριο Ανώτερης Γεωδαισίας	el
heal.academicPublisherID	ntua
heal.numberOfPages	198 σ.	el
heal.fullTextAvailability	false