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Gravity and magnetic survey of the east tectonic boundary of Cheb sedimentary basin
Buřičová, Pavla ; Blecha, Vratislav (advisor) ; Beneš, Vojtěch (referee)
Region of West Bohemia and the neighbouring German area Vogtland is characterized by its recent seismic activity. For better understanding of the distribution and origin of earthquake swarms it is necessary to know in detail the shallow as well as deeper geological structure of this area. This thesis deals with the geological and tectonic situation between villages Kopanina and Nový Kostel. In this area Mariánské Lázně Fault, which represents - from our point of view - the eastern marginal fault of the Cheb basin, is crossed with the fault zone Počátky - Plesná. The greatest amount of earthquakes hypocenters on the territory of Czech Republic have been registered in this region. The aim of this thesis is not only to find the eastern marginal fault of the Cheb basin, but also to define its course in the terrain and to determine its slope. Geophysical methods gravimetry, magnetometry and conductometry have been applied to identify these fault parameters. Geophysical methods were measured on three paralel profiles in August 2010 and in June 2011. The data from these profiles were consequently processed and geologically interpreted. During interpretation it was shown that contribution of magnetometry to recognition of different rock types and to identification of tectonic features was poor. On the...
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GRAVITY, MAGNETIC AND PETROPHYSICAL SURVEY OF DIFFERENT GRANITE TYPES OF THE KARLOVY VARY PLUTON
Šobotník, Petr ; Blecha, Vratislav (advisor) ; Marek, František (referee)
The thesis is a part of project "Gravity model of the Karlovy Vary granite pluton", The project is solved at the Faculty of Science, Charles University, Prague and it is supported by Grant Agency of the Czech Republic, grant 205/05/0156. The Karlovy Vary pluton is a part of larger body, The Krušné Hory Mts. pluton, which probably occurs beneath whole area of the Krušné Hory Mts. In the western part of these mountains The Karlovy Vary pluton forms a large outcrop of the granite body. The granites are source of a remarkable regional gravity low. Granites intruded in time interval of several milion years during and after a main deformation phases of the Variscan orogenesis. With regard to age, we recognize two main types and a lot of subtypes of granites. These types are different not only in their ages but also in geochemical composition. We studied if different types of granites are distinguishable also in petrophysical properties and in geophysical measurements in the field. Chosen methods were gravimetry and magnetometry. We measured a 3500 m long profile at the locality close to the Karlovy Vary town, where three types of the granites occur: Older Intrusive Complex (OIC), Younger Inrusive Complex (YIC) and transition type of the granite - microgranite (porhyric granite). Gravity measurements were...
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Nature of magnetic anomalies on Moon, sample analysis
Kameníková, Tereza ; Kletetschka, Günther (advisor) ; Blecha, Vratislav (referee)
The magnetic properties of a rocks on Earth are mostly well known. But what is the magnetic properties of a rocks which originate extraterrestrial? Such as on Moon. We are interested in the intensity of paleofield of some Moon rocks which were chipped by Apollo 15 in early 70s. The text is an unification of the basic knowledge of a magnetism, the way how it originates. You can found here also the basics of paleomagnetism and methods how the rocks can get own magnetisation, their properties and some outline how the Moon rocks can get own magnetisation if moon doesn't have a dynamo. Then we summaries the information got from measurements of two Moon rocks 15404.219 and 15445.277, which were divided to subsamples and measured in Paleomagnetic laboratory in Czech Academy of Sciences. Each subsample was measured separately on 2G cryogenic magnetometer. We were interested in AF (alternating field) remanent magnetisation spectra from which we got an estimating intensity of paleofield from which the samples got own magnetisation. The final part is devoted to discussion on topic of possible existence of lunar dynamo or other possibilities how the Moon rocks can have held the magnetisation.
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Gravity survey and modeling of geological structures
Beránek, Roman ; Blecha, Vratislav (advisor) ; Beneš, Vojtěch (referee)
This thesis deals with the application of gravity survey to detect and delineate geological structures. The thesis further deals with various processing and interpretation methods, which include the creation of computer-generated models. To meet these goals, the gravity measurement was carried at the locality with the expected presence of abandoned historical mineshaft of known orientation. The goal is therefore to clarify and scrutinize information gained from various historical sources. Different models of survey area were made during the interpretation phase of the survey including 2D and 3D models according to the unknown recent state of the mineshaft. The result of this study is a comparison of several different approaches used in gravity surveys such as methods of elevation measurements, residual drift approximation, regional-residual field separation, source depth estimation, and modelling.
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Verification, analysis and interpretation of gravity anomaly at locality Žírovice in the Cheb Basin
Vaško, Oskar ; Mrlina, Jan (advisor) ; Blecha, Vratislav (referee)
In the vicinity of the Žírovice village near Františkovy Lázně in West Bohemia there exists a striking gravimetric isometric negative anomaly. Similar gravimetric anomaly near Mýtina, about 17 km to the SE of Žírovice, was interpreted by Mrlina et al. (2009) as a Quaternary volcanic structure of a maar-diatreme type. It is possible that the Žírovice anomaly and some other similar anomalies in the Cheb Basin may also reflect Tertiary or Quaternary volcanic structures. For this reason we performed a detailed gravimetric and magnetometric survey, followed by geophysical modeling. The presence of a volcanic structure was not confirmed by this work, on the contrary, it was rather excluded. The anomaly was interpreted as a sunken tectonic 3D block/graben.
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