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Temporal gravity changes related to geodynamic phenomena and geomechanical processes
Mrlina, Jan ; Blecha, Vratislav (advisor) ; Novotný, Oldřich (referee) ; Pašteka, Roman (referee)
My Thesis is based on five papers dealing with gravity changes related to various geodynamic, geomechanical and hydrological processes and phenomena. In the first part of the Thesis the gravity changes are defined as a geophysical quantity. The two principal causative parameters are highlighted - variation in elevation of the earth surface, and temporal excess of mass (negative or positive) in the subsurface. I also discuss different groups of parameters and environmental phenomena disturbing the gravity measurements, as the data accuracy is an essential condition of gravity monitoring (4D gravity). I performed a special test with the LaCoste&Romberg D-188 gravimeter in a pressure chamber with notable result showing negligible impact of small and medium size air-pressure variations on this instrument. The calibration stability was proved during two world comparison/calibration campaigns of absolute and relative gravimeters in Sevres, France. The instrument's repeatability was evaluated as 2 μGal (0.02 μm/s 2 ). As well, calibration is being controlled by measurements on the Czech latitude calibration line between Prague and Dolní Dvořiště in South Bohemia. In order to achieve best accuracy we developed special software Drift to control the gravimeter's drift. In principle the software provides a...
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Temporal gravity changes related to geodynamic phenomena and geomechanical processes
Mrlina, Jan ; Blecha, Vratislav (advisor) ; Novotný, Oldřich (referee) ; Pašteka, Roman (referee)
My Thesis is based on five papers dealing with gravity changes related to various geodynamic, geomechanical and hydrological processes and phenomena. In the first part of the Thesis the gravity changes are defined as a geophysical quantity. The two principal causative parameters are highlighted - variation in elevation of the earth surface, and temporal excess of mass (negative or positive) in the subsurface. I also discuss different groups of parameters and environmental phenomena disturbing the gravity measurements, as the data accuracy is an essential condition of gravity monitoring (4D gravity). I performed a special test with the LaCoste&Romberg D-188 gravimeter in a pressure chamber with notable result showing negligible impact of small and medium size air-pressure variations on this instrument. The calibration stability was proved during two world comparison/calibration campaigns of absolute and relative gravimeters in Sevres, France. The instrument's repeatability was evaluated as 2 μGal (0.02 μm/s 2 ). As well, calibration is being controlled by measurements on the Czech latitude calibration line between Prague and Dolní Dvořiště in South Bohemia. In order to achieve best accuracy we developed special software Drift to control the gravimeter's drift. In principle the software provides a...
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Complex interpretation of gravity data focused on tectonic structure assessment and environmental projects
Mantlík, František ; Kobr, Miroslav (advisor) ; Blecha, Vratislav (referee) ; Pašteka, Roman (referee)
3 Abstract Gravimetry is an enormously expanding geophysical exploration method during the last decade. Unfortunately the gravity inversion ambiguity problem introduces the necessity to constrain gravity model parameters by other independent data. Overview of gravity data processing and interpretation is presented. All stages of the project lifecycle are discussed with emphasis to the methodological aspects and new challenges introduced by common use of modern digital zero-length spring gravimeters. Special attention is drawn on approaches used in the presented case histories projects. Description of the interpretation stage of the project concentrates on constraining of gravity model parameters with a complex of geophysical and geological data in order to reduce ambiguity of the inversion process in gravimetry. In addition, approaches used for delineation of tectonic structures, an important aspect of the interpretation stage, are described. Three case histories examples are presented to demonstrate methodological aspects of the interpretation of gravity data. They are focused on environmental problems and tectonic structure assessment. The first project represents an attempt to use micro-gravity for determination of internal structure of an undocumented sealed landfill. The second project demonstrates...
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