|
| |
|
|
Inversion and Depth Range of Dipole Electromagnetic Induction Measurements in Geophysics
Moura de Andrade, Fernando César ; Fischer, Tomáš (advisor) ; Godio, Alberto (referee) ; Velímský, Jakub (referee)
Inversion and Depth Range of Dipole Electromagnetic Induction Measurements in Geophysics Fernando César Moura de Andrade Institute of Hydrogeology, Engineering Geology and Applied Geophysics Faculty of Science, Charles University Electromagnetic induction geophysical methods are, basically, composed by a transmitter which produces a magnetic field and a set of receivers which measure the primary magnetic field, from the transmitter, superimposed by secondary magnetic fields inducted in the subsurface. Equipment operating at, relatively, low frequencies and with short distances between the transmitter and the receivers are usually called conductivity meters and operate at low inductions numbers. The depth of investigation, in such kind of equipment, depends mainly on the transmitter-receiver distance, on the orientations of the magnetic dipoles and the height of the instrument from the ground, in order that a depth sounding can be done changing these parameters in a single measurement location. Making a series of these multi-configuration measurements, two-dimensional, or even three-dimensional surveys, can be performed and, subsequently, inverted in order to produce an image of the subsurface of the earth. Forward modelling and inversion of multi-configuration electromagnetic induction data can be made...
|
|
|
Relocation of the 1962 earthquake swarm in West Bohemia
Konrádová, Diana ; Fischer, Tomáš (advisor) ; Doubravová, Jana (referee)
Since the swarm at the turn of 1985/86 the current activity of seismic swarms in western Bohemia takes place mainly in the area of Nový Kostel at the eastern edge of the Cheb basin. However, the location of previous activities, where only more remote seismic stations were in operation, is not exactly known. This also applies to the swarm of 1962, which this bachelor thesis is focused on. Seismic bulletin data are available from eight seismic stations at a suitable distance for sufficient localization quality for this swarm. The theoretical part of the thesis presents research results of fundamental existing localization methods and their properties. In the practical part, the location of the earthquake epicenter of swarm 1962 is presented.
|
|
|
Automated determination of earthquake source parameters
Vackář, Jiří ; Zahradník, Jiří (advisor) ; Evangelidis, Christos (referee) ; Fischer, Tomáš (referee)
Title: Automated determination of earthquake source parameters Author: Jiří Vackář Department: Department of Geophysics Supervisor: prof. RNDr. Jiří Zahradník, DrSc., Department of Geophysics Abstract: The thesis deals with methods for automated inversion of seismic source parameters. We studied the influence of structure model used and show an ex- ample how the existing model can be improved. We have developed a new, fully automated tool for the centroid moment tensor (CMT) inversion in a Bayesian framework. It includes automated data retrieval from ArcLink server or local data storage. Step-like disturbances are detected using modeling of the distur- bance according to instrument parameters and such components are automati- cally excluded from further processing. Frequency ranges for the filtration and time windows for the inversion are determined automatically due to epicentral distance. Full-waveform inversion is performed in a space-time grid around a provided hypocenter. A data covariance matrix calculated from pre-event noise yields an automated weighting of the station recordings according to their noise levels and also serves as an automated frequency filter suppressing noisy frequency ranges. The method is tested on synthetic and observed data. It is applied on a dataset from the Swiss seismic...
|
|
|
Earthquake influence on groundwater levels in West Bohemia/Vogtland
Krajinová, Markéta ; Fischer, Tomáš (advisor) ; Horálek, Josef (referee)
This Batchelors thesis focuses onto possible earthquake influence on groundwater levels in West Bohemia/Vogtland area. The thesis describes geology, hydrogeology and seismic activity of the area. Further describes possible earthquake influence on ground water level and mentions world and local sightings. The area is known for its earthquake swarms up to ML=4, therefore the thesis also deals with an influence of three local earthquakes. They occurred in 2014 with hypocentre near Nový Kostel in West Bohemia and their magnitudes were ML =3,5; 4,4 and 3,6. The thesis further analyses ground water level records of 38 wells at localities: Františkovy Lázně, Lázně Kynžvart, Karlovy Vary, Německo and sokolovská pánev. A polarity of ground water level change after the earthquakes is compared to volumetric strain caused by the earthquakes. Overall agreement is found at few sites, which indicates possible effect of earthquake generated static stress change to the ground water level.
|
|
| |
|
| |
|
|
Recent movements on the Cordillera Blanca fault (Peru)
Sánchez Valdiviezo, Lisseth del Pilar ; Fischer, Tomáš (advisor) ; Burjánek, Jan (referee)
The studied area is located the Cordillera Blanca range (central Peru). This mountain range is, at its western foot, bordered by a 210 km long fault system bearing the same name. It is on this fault system where 3D monitoring of recent movements with the use of dilatometer TM-71 takes place. Displacements along this fault are analyzed with regard to the static stress changes caused by earthquakes. Moreover, processing and interpretation of data from ERT measurement performed across the investigated fault at Pitec locality (10 km from Huaraz) are presented. The resulting geoelectrical models of the measurement carried out in July 2016 at the mentioned locality indicate that this area is formed by rocks with very high resistivity values. It is a consequence of the presence of the moraine material (7 to 12 m thick) and of the base of the colluvial deposits composed of granites and granodiorites. At this site the fault has a dip angle of 70ř. The 3D displacement monitoring results of the studied fault at the Pitec locality indicate that the selected site is generally very stable. The dilatometer TM-71 has been in operation since 1997 and has been measuring movements on the Cordillera Blanca fault in all the three dimensions (perpendicular to the fault - opening, along the fault in horizontal plane,...
|
|
| |
|
|
Possibilities of hydraulic fracturing in geothermal energy exploitation
Pokorný, Jakub ; Fischer, Tomáš (advisor) ; Horálek, Josef (referee)
Hydraulic stimulation is a technique used to increase the permeability of reservoir formation by creation of new and connection of existing cracks. The aim of this bachelor thesis is to collect and explain the basic principles of continuum mechanics and fundamentals of fluid hydraulics that are an integral part of the overall understanding of the issue of stimulation and its later more detailed study. After a general introduction, these findings are put into context in terms of mechanism of rock fracturing and fluid flow in the emerging stimulated geothermal systems. This thesis is completed by placing the example of geothermal project Groß Schönebeck from the start of stimulation to the final hydraulic tests, which were carried out with the aim of assessing the efficiency of fracture permeability enhancement. Powered by TCPDF (www.tcpdf.org)
|
guest ::
