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GPR data interpretation with use of a combined geoelectrical survey
Široký, Jakub ; Tábořík, Petr (advisor) ; Valenta, Jan (referee)
GPR data interpretation is often difficult due to complex geological environments, reflections ambiguity and time-depth conversion uncertainty. Thanks to the geophysical fields interoperability it is possible to compare results of related survey methods. Radargrams from three model sites were processed and interpreted in an usual way to uniformly amplify all recorded reflections. Results were compared with ERT and EM (DEMP) data within integrated interpretation. GPR data interpretation was extended and new geological and geomorphological interpretations were uncovered. The GPR processing sequence was modified and simplified following outcomes from the integrated interpretation to ease different methods results comparison. Adapting a velocity model to precise time- depth conversion hasn't showed improvements. Key words: ground penetrating radar, electrical resistivity tomography, dipole electromagnetic profiling, integrated interpretation, integrated inversion, GPR processing optimization, sedimentary environment, velocity model
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Using ERT and GPR in polygonal patterned ground analysis
Široký, Jakub ; Křížek, Marek (advisor) ; Hartvich, Filip (referee)
Polygonal cryogenic structures cannot be investigated with conventional methods as they could be harmed during measurement. A real3D GPR and ERT non-destructive surveys were used to examine and prove applicability for topsoil covered ice-wedge pseudomorphs and coarse-grained sorted polygons (patterned ground). A list of processing tools and algorithm suitable for such environments was created and tested. The benefits of 3D measurements are illustrated on horizontal slices and pseudo3D visualisation of 3D Cube. Basic morphometry characteristics of both forms were collected. Abilities of geophysical imaging for advanced shape characterisations are discussed, too. The low-frequency measurements gave better results at both sites. Pseudomorphs, 2 wide and up to 6,5 long, were found penetrating depth bigger than 3,5 . Sorted polygons, 2,5 wide in diameter, were depicted locked by stony ring of width around 1 . Sorting depth extends up to 0,54 depth for sure, perhaps more.
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Time-lapse monitoring of active slope deformations using electrical resistivity tomography
Belov, Tomáš ; Tábořík, Petr (advisor) ; Kněz, Jaroslav (referee)
The diploma thesis deals with time-lapse electrical resistivity tomography (TL-ERT) of active slope deformations. Slope deformations represent one of the important land-forming processes. Frequently, they can cause considerable property damages and can endanger health and lives of inhabitants. Therefore, we can consider them as potentially dangerous so complete understanding of their dynamics, and their mechanisms of origin, is essential. Electrical resistivity tomography (ERT) then represents an effective geophysical tool for slope deformation investigation. Within diploma thesis, the evaluation of the several different time-series of the ERT measurements was performed. Based on findings of the one- year (August 1013 to July 2014) monitoring of resistivity changes by ERT, and also, based on daily and hourly recurrences of measured resistivity data, the optimum measuring interval has been determined, namely 12 hours. The most applicable electrode arrays and their combinations were suggested based on a testing of different electrode configurations. The results of detailed measurement with 1 m electrode spacing offered the idea of shortening of the total length of the present permanent TL-ERT profile as well as shortening the electrode spacing. These conclusions and proposed adjustments then resulted in...
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Geophysical survey of subsurface voids at locality Letonice
Bartášková, Lucie ; Blecha, Vratislav (advisor) ; Skácelová, Zuzana (referee)
The Větrníky national nature reserve, located in the South Moravian region north of the village of Letonice, is one of the largest steppe reserves in Southern Moravia. This whole area is characterized by the presence of both stable and active landslides, and the occurrence of suffosion sinkholes has been monitored there in the long-term. The aim of the thesis was to investigate whether it was possible to observe subsurface phenomena, caused by the washing out of fine rock particles by ground water, by means of geophysical methods. This phenomenon is known as suffosion. The measurements took place in the areas where the suffosion manifestation was very distinctive, that is around two sinkholes that were visible on the surface. In order to identify the suffosion structural-geological causes and their manifestations at a given location, the gravimetric and electrical resistivity tomography (ERT) methods were used in the first stage of the research. Measured data was further processed and geologically interpreted. The gravimetric method has proved suitable when identifying rocks affected by suffosion, in which case we assume that their density is lower than the density of the surrounding rocks. Using the ERT method, it was possible, in the vertical profile, to distinguish the sandy-gravelly sediments...
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Analysis of the subsurface struckutes location in representative transections of the research catchments
DUBEC, Štěpán
This theses is focused on the description of subsurface in the area of interest - Kopaninský and Jenínský stream catchment - and consequently thy most accurate interpretation depth of impermeable bedrock. Geophysical multicable metod (ERT - electrical resistivity tomography") was selected for field measurements. This method of geophysical survey provides the information on subsurface structures, verifies hypotheses and brings new information on the lithological and structural conditions below the surface. ERT measurements were performed automatically by geoelektrical ARES device in combination with inteligent electrodes. The data obtained by field measurements were plotter in the form of resistive sections (using ReS2DInv software) which were used for the later interpretation. The given results determine the depth and process of impermeable bedrock which are important for more accurate data inputs like for modeling rainfall-runoff processes especially in the field of calibration and validation of each adjustment of models as well as for the next other hydrogical analyzes and studies carried out in the research projects. The purpose of this work is to determine the depth of impermeable bedrock and could serve as a data input for MIKE SHE hydrological modeling.
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Methods for determining the depth of impermeable bedrock as a basis for hydrological reserch.
DUBEC, Štěpán
This thesis is focused on the description of subsurface structures in the area of interest - Kopaninský stream catchment - and consequently the most accurate interpretation depth of bedrocks. Geophysical multicable metod (ERT ?electric resistivity tomography?) was selected for field measurements. This method of geophysical survey provides the information on subsurface structures, verifies hypotheses and brings new information on the lithological and structural conditions below the surface. ERT measurements were performed automatically by geoelectrical ARES device in combination with intelligent electrodes. The data obtained by field measurements were plotted in the form of resistive sections (using RES2DINV software) which were used for interpretation. The result of this work is to determine the depth of bedrocks and should serve as a data input for MIKE SHE hydrological modeling.
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