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Injection-induced seismicity: statistic and energetic analysis
Vlček, Josef ; Fischer, Tomáš (advisor) ; Horálek, Josef (referee)
Fluid injection into the rock formations represents a valuable analog to study the role of high-pressurized fluids in the seismogenic process. It is carried out in depths up to first thousands of meters in order to increase the permeability of rock formation for better exploitation of hydrocarbons and geothermal energy. The increased fluid pressure results in decrease of the strength of fractures and faults which causes their brittle failure that is observed in the form of microearthquakes and enables imaging of the stimulated rock volume. Besides this positive role, seismicity sometimes increases to the level that can be felt by the population, which can cause concerns about the seismic risk of these industrial operations. Thus, one of the main interests focused by recent studies deals with the maximum earthquake that can be triggered by hydraulic stimulations. I introduce the ratio between the hydraulic energy and released seismic energy, the seismic efficiency of injection, to assess the effect of fluid injection to the seismicity. This parameter is applied to data from two geothermal reservoirs (Gross Schönebeck and Soultz-sous-Forets) and one gas reservoirs (East Texas). We find that for different data sets, the seismic efficiency encompasses a broad range of magnitudes; from about 10-6 to...
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Earthquake swarms in diverse tectonic environments: West Bohemia and Southwest Iceland
Jakoubková, Hana ; Horálek, Josef (advisor) ; Cesca, Simone (referee) ; Málek, Jiří (referee)
In my doctoral thesis I have investigated earthquake swarms from two com- pletely different tectonic areas, West Bohemia/Vogtland and Southwest Iceland, with the aim of gaining a deeper insight into the nature of earthquake swarms in diverse tectonic environments. I analysed swarm-like activities from West Bo- hemia and Southwest Iceland from the perspective of statistical characteristics (magnitude-frequency distribution, interevent time distribution), seismic moment release, and space-time distribution of events. I found that the ratio of small to large events and the event rates are similar for all the activities in both areas, while the rate of the seismic moment release is significantly higher for the South- west Icelandic swarms. Seismic moment released step by step is characterised for the West Bohemia swarms, whereas seismic moment released in one dominant short-term phase is typical of Southwest Icelandic earthquake swarms. All the West Bohemian swarms took place in a bounded focal zone Nový Kostel that is fairly complex, consisting of several fault segments. The Southwest Icelandic swarms are distributed at much larger area along the Mid Atlantic Ridge up to its branching in the Hengill triple junction, the individual swarms clearly reflect a tectonic structure of respective focal areas. I have...
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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.
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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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Relation of earthquakes and volcanism in West Bohemia and Iceland
Labuta, Martin ; Horálek, Josef (advisor) ; Hrubcová, Pavla (referee)
English abstract Most earthquakes occur as accompanying activity of large tectonic earth- quakes at the edges of lithospheric plates. Another type of seismic activity are earthquake swarms, which are characterized by series of earthquakes with several dominant shocks of similar strength. The origin of earthquake swarms is mostly combination of tectonic stress and movement of hydrothermal flu- ids along the fault plane. Mainly, swarms are observed within volcanic areas but even in areas without recent volcanic activity, like in West Bohemia. This region lies above an intra-continental rift zone the Eger Rift and it has been seismologically active in past years, including swarms in 2008, 2011, 2013 and 2014 monitored by the local seismic network WEBNET with dominant shocks of magnitudes below ML 4.5. All these events are located in depths between 7 and 11 km and they create 8 km long focal zone with N-S orientation. However, the latter swarm changed its character from a continuous occurrence with a dominant shock to a main shock and aftershock activity. Contrary, the region of Reykjanes peninsula in Iceland is located above the Mid-Atlantic Ridge, which results in shallower depths between 2 to 9 km. Additionally, the seismic energy in this area is released as a typical swarm-like activity and migrates along...
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Injection-induced seismicity: statistic and energetic analysis
Vlček, Josef ; Fischer, Tomáš (advisor) ; Horálek, Josef (referee)
Fluid injection into the rock formations represents a valuable analog to study the role of high-pressurized fluids in the seismogenic process. It is carried out in depths up to first thousands of meters in order to increase the permeability of rock formation for better exploitation of hydrocarbons and geothermal energy. The increased fluid pressure results in decrease of the strength of fractures and faults which causes their brittle failure that is observed in the form of microearthquakes and enables imaging of the stimulated rock volume. Besides this positive role, seismicity sometimes increases to the level that can be felt by the population, which can cause concerns about the seismic risk of these industrial operations. Thus, one of the main interests focused by recent studies deals with the maximum earthquake that can be triggered by hydraulic stimulations. I introduce the ratio between the hydraulic energy and released seismic energy, the seismic efficiency of injection, to assess the effect of fluid injection to the seismicity. This parameter is applied to data from two geothermal reservoirs (Gross Schönebeck and Soultz-sous-Forets) and one gas reservoirs (East Texas). We find that for different data sets, the seismic efficiency encompasses a broad range of magnitudes; from about 10-6 to...
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Historical seismicity and geophysical survey of tectonics in the Cheb area
Hrdličková, Markéta ; Fischer, Tomáš (advisor) ; Horálek, Josef (referee)
This work deals with the documentation of the space-time distribution of seismic activity in the years 1897-1908 in the western Bohemia, using original sources. The region of Vogtland / northwest Bohemia is known as one of the most interesting European regions with the occurrence of earthquake swarms. Seismic catalogs are available for this area only for the last few decades when the seismic stations were in operation. For the earlier period only macroseismic observations are available. The aim of this work is to compile the catalog of earthquakes for the years 1897-1908 with the use of the macroseismic data. This requires estimating the origin time of earthquakes using the distribution of the macroseismic observations in time. First, the original historical materials Mittheilungen der Erdbeben-Commission der kaiserlichen Akademie der Wissenschaften in Wien were compared with geophysical catalog of Vít Kárník Erdbebenkatalog der Tschechoslowakei bis zum 1956, which is a summary of selected data from the original materials. Macroseismic observations from the catalog were digitized in the form spreadsheet tables. It turned out that in most cases the data in the Kárník's catalog represent observations of earthqukes and in isolated cases these are the seismic events themselves. Cluster analysis was...
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New interactive software for seismic data processing
Doubravová, Jana ; Horálek, Josef
Seismon is an open source software package under GNU General Public Li- cense developed by Stefan Mertl (TU Wien). It is designed as a modular pro- gram with de ned interface for speci c types of modules. This gives program- mer rules how to add new tools easily without disturbing the program integrity. Seismon is written in MATLAB and all input and output data are stored in MySQL database which can be accessed by more Seismon users simultaneously. Seismon is initially equipped with tools for communication with the database, various waveform le conversions, and basic tools for data analysis and visual- ization. To use this software for routine processing of data from local seismic network in West Bohemia (WEBNET), some adaptations had to be done, and the modi ed program was called Seismon_WB. There had to be put a great emphasis on user friendliness which required to de ne keyboard shortcuts, add status bars directly displaying current possibilities and properties, or extract the most important functions out of structured menus to main window as GUI components.
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