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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,...
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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)
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Source Parameters of Microearthquakes and their Uncertainties
Michálek, Jan ; Fischer, Tomáš (advisor) ; Gallovič, František (referee) ; Kwiatek, Grzegorz (referee)
Title: Source Parameters of Microearthquakes and their Uncertainty Author: Jan Michálek Department: Department of Geophysics Supervisor: Doc. RNDr. Tomáš Fischer, PhD., Institute of Hydrogeology, Engineering Geology and Applied Geophysics, Charles University in Prague Abstract: The aim of this thesis is to analyze the spectral methods used for the determination of the earth- quake source parameters like the seismic moment M0 and the corner frequency fc and to apply these meth- ods to seismic data from the West Bohemian region. Considering some assumptions about the source the other important parameters like the source radius r or the stress drop in the source ∆σ can be evaluated. Determination of the parameters is performed in the spectral domain by comparing a simple Brune's source model (non-causal slip on a circular rupture; spectral slope ω−2) with the displacement of the P or S wave. The methods were applied to 56 selected earthquakes of the West Bohemian swarms from 2000 and 2008 by the absolute and relative approach in several modifications. The absolute method allows to determine not only the source parameters but also the quality factor Q (attenuation), which significantly affects the deter- mination of fc. Therefore, the absolute method was applied also as the joint inversion when Q is stabilized....
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Laboratory study of 3D elastic anisotropy of rocks
Svitek, Tomáš ; Lokajíček, Tomáš (advisor) ; Fischer, Tomáš (referee) ; Pšenčík, Ivan (referee)
12 Abstract The presented work evaluates the significance of measuring acoustic S-wave velocities for determination of elastic anisotropy of rocks. The S waves are more sensitive to anisotropic properties of a medium than the P waves. Analyzing the S-wave splitting, it is possible to determine strength of anisotropy as well as the orientation of structures responsible for the anisotropic behavior of the medium. The S waves are necessary for determining the complete tensor of elastic parameters. In order to record the S waves, the measuring head of the present apparatus has been significantly adapted. Implemented innovations provided measurements of the P waves together with two orthogonally polarized S waves. The calibration performed on homogeneous isotropic materials proved that the recorded data are accurate and of high quality. The ultrasonic measurements on spherical samples under confining pressure and recording of the S waveforms significantly improved the accuracy of the retrieved elastic parameters compared to the measurements in standard use. The analysis of the S-wave records also required modifications of the processing software and a development of new algorithms. The proposed methods were tested on synthetic data. The tests evaluated the robustness of the inversion for anisotropy as a function...
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Seismic activity in Peru
Sánchez Valdiviezo, Lisseth del Pilar ; Fischer, Tomáš (advisor) ; Jakoubková, Hana (referee)
This bachelor thesis approaches seismicity in Peru. It describes the origin of tectonic earthquakes and provides a general description of the basic concepts of seismology. This thesis work is mainly focused on a detailed characterization of seismic activity in Peru. It includes a complete description of the geodynamics of the Peruvian territory, the evolution and distribution of seismicity in this South American country and its geomorphological units.
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Seismograph installation and complex analysis of recorded data
Vaško, Oskar ; Fischer, Tomáš (advisor) ; Hrubcová, Pavla (referee)
This thesis deals with assembly of a school seismograph and a common analysis of recorded data. A garden-gate type seismometer was assembled within the first part of my thesis. The pendulum construction of the seismometer enables recording of a horizontal component of seismic signal. The data analysis involves mainly processing of seismic noise in the buiding of Geologic Section of Faculty of Science in Prague - Albertov. Several eigenfrequencies of the building, which indicate the liability of the construction to be affected by ground motions, were found. As a supplement few recorded earthquakes were identified. The seismic noise analysis led to a finding of a relation between eigenfrequency variation and outdoor temperature in the form of a positive correlation between daily temperature average and eigenfrequency.
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Magnitude calibration of seismic network WEBNET
Kolář, Dominik ; Fischer, Tomáš (advisor) ; Jakoubková, Hana (referee)
This thesis deals with determination of seismic magnitudes of West-Bohemian earthquakes. The first part summarizes basic information from the field of seismology and also about the earthquake swarms in the area of interest. The second part deals with calibration of magnitudes, i.e. determination of coefficient that corrects for attenuation and station corrections. Seismic data from the WEBNET network from 2012 were used to this purpose. In order to suppress tradeoff among the studied parameters the data were filtered and also usage of a fixed hypocenter depth was tested. The results show that the optimum attenuation correction is smaller than that used so far magnitude determination. It turns out that a deeper analysis is needed in order to find an optimum formula for magnitude determination at the West-Bohemia WEBNET network.
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Analysis of coda waves of the West-Bohemian earthquakes
Bachura, Martin ; Fischer, Tomáš (advisor) ; Vavryčuk, Václav (referee)
Coda of high frequency earthquakes contains information about attenuation propetries of the environment between earthquake hypocentre and seismic station. By application of different methods of coda anlysis one can derive these properties. I applied three methods to seismograms from autumn 2011 from WEBNET network monitoring seismic activity in West Bohemia/Vogtland area: basic method to derive Qc parameter of the environment, and two methods that allow for separation of intrinsic attenuation (Qi) and attenuation due the scattering (Qsc): method MLTWA (Multiple Lapse Time Window Analysis) and method based on energy flux model. Values of Qc are relatively small (from 22 to 600, which depends on the length of the window in which the analysis is carried out and on the frequency and station used), which is in good agrement with the high seismic activity in the area. Qc shows frequency, depth and lateral dependances. It increases with frequency and depth and in the southwest direction. The applicability of methods for separation of Qi and Qsc are limited. With short hypocentral distancies as we have coda is not affected by scattering. Because of this, I was unable to use MLTWA method and the method of energy flux model was usable to derive only the values of Qi. These values are from 120 (1,5 Hz at...
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Earthquake source models
Adamová, Petra ; Šílený, Jan (advisor) ; Fischer, Tomáš (referee) ; Gallovič, František (referee)
The earthquake source is routinely modeled by moment tensor description. In many cases we need more information about the source process and for that reason we occupy with higher degree moments. This approach allows us to esti- mate non-point characteristics (including some dynamic parameters): geometry of the source, duration of the source process, average slip on the fault, spatial and temporal centroid and rupture velocity vector within the point source ap- proach. This description includes 20 parameters - 6 parameters for standard moment tensor (MT) and 14 parameters for second degree moments (SDM). First, we studied synthetic tests. Large amount of significant earthquakes con- tains false non-DC component which can be caused by approximation finite source by point source. This hypothesis was proved on the case of unilateral rupture. Standard MT contains more than 20 % non-DC components which was reduced to 6 %. In the second part we applied this procedure to real data. We chose large earthquakes (Mw>6) with large non-DC component. We estimated second degree moments for them and compared them with previous studies. Moreover we restitute higher degree moments from data and proved that false non-DC component were caused by source finiteness. In the last part we applied this method to mining data and...
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