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Dynamic models of earthquake source and modeling of seismicity
Kostka, Filip ; Gallovič, František (advisor) ; Matyska, Ctirad (referee)
In the present thesis we perform modeling of earthquake source using laboratory derive rate-and-state laws of friction. We have developed a code in Fortran 90 for modeling a planar, two-dimensional fault with general dip and heterogeneous distribution of frictional parameters. We use a quasi-dynamic approximation and assume that the fault is submnerged in an infinite elastic half-space. We performed an extensive number of numerical experiments to study the effect of fricitonal parameters distribution on the spatio-temporal complexity of slip on fault. We also study the effect of the so called Coulomb stress changed on clock advance and clock delay of events. For this purpose we use both a homogeneous model and a model of random frictional parameteres which exhibits the Gutenberg-Richter frequency- size dependence in the range of two magnitudes. We find that the effect of Couloumb stress change is nontrivial and depends on factors such as the domain of stress load and the slip velocity on it. Powered by TCPDF (www.tcpdf.org)
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Moment-tensor inversion of earthquakes in Greece, method ISOLA
Křížová, Dana
3 Title: Moment-tensor inversion of earthquakes in Greece, method ISOLA Author: Dana Červinková Department: Department of Geophysics Supervisor: Prof. RNDr. Jiří Zahradník, DrSc. Supervisor's e-mail address: jz@karel.troja.mff.cuni.cz Abstract: The possibility of obtaining a reliable moment tensor using a low-frequency waveform inversion from a single seismic station is studied. Deviatoric part of the moment tensor is described in usual way, using its orientation (angles strike, dip, rake), scalar seismic moment M0 and the double-couple percentage (DC%), and also by means of the coefficients of linear combination of elementary mechanisms. We estimate the formal error of the coefficients and study conditionality of the inverse problem. Data from earthquakes Trichonis (Mw = 5.2, April 2007) and Leonidio (Mw = 6.2, January 2008), Greece, are processed using software ISOLA (Sokos and Zahradník). The moment tensor is calculated from many stations and its stability is tested. This reference solution is compared to those independently obtained from single stations. Synthetic tests are performed to understand why the single-station estimates are sufficient for Trichonis, but not for Leonidio, paying attention to the focal depth, station azimuth and epicentral distance. It is found that the depth is crucial at...
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Seismic analysis of structure with residual modes
Včelný, Michal ; Martinásek, Josef (referee) ; Vlk, Zbyněk (advisor)
This thesis deals with the possibility of using the residual shape with help of the structural analysis software SCIA Engineer in the calculation of seismic load. Residual shape will be used in combination with CQC and SRSS calculation method, including different numbers of own shapes and the oscillated mass. In the last step, the results will be compared with each other.
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Využití kapacit klastrů při řešení humanitární krize - případová studie Haiti
Jungová, Marie
Devastating earthquake on Haiti with an epicenter only 15 kilometers from the capital city, which has damaged west coast part of country, has seen decline in living standards by about 28 % of residents of Haiti. Submitted thesis which solves theoretical approach to cluster distribution proved on the main shortages and reasons arise humanitarian crisis which were given by decrease of akcesibility, decrease of distribution ability, inability to receive the help sent and delayed response by the government. Incapacity was exacerbated by the fact that some members of the managing authority were killed. Since, in view of the fact that level of readiness was low and limited to a low number of state administration employees, they were not able to react and secure the reception of help and services. During the humanitarian crisis 230 000 people died.
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Development of effective code for earthquake dynamic source simulations
Premus, Jan ; Gallovič, František (advisor) ; Zahradník, Jiří (referee)
Title: Development of effective code for earthquake dynamic source simulations Author: Bc. Jan Premus Department: Department of Geophysics Supervisor: doc. RNDr. František Gallovič, Ph.D, Department of Geophysics Abstract: Dynamic rupture modeling coupled with strong motion data fitting offers an insight into physical mechanisms behind earthquake sources [Gallovic et al., 2019]. Running a large number of dynamic model simulations is required due to the nonlinearity of the inverse problem. The goal of this Thesis is a development of an efficient forward solver for the dynamic inversions. The fi- nite difference staggered grid code FD3D by Madariaga and Olsen [1998] served as a basis for the development, offering sufficient speed, but rather low accu- racy. Traction at split node implementation of the fault boundary condition and perfectly matched layers as the absorbing boundary condition were required to obtain desirable accuracy. In addition to the slip weakening friction law, fast ve- locity weakening friction law has been implemented, increasing the applicability of the code. We test the new code FD3D TSN using USGS/SCEC benchmarks TPV5 (slip-weakening friction) and TPV104 (fast rate weakening friction) [Harris et al., 2018], showing very good agreement with results calculated by advanced numerical...
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Analysis of rupture velocity for selected earthquakes utilizing regional recordings of surface waves
Čejka, František ; Gallovič, František (advisor) ; Zahradník, Jiří (referee)
Supershear earthquake is an interesting phenomena that is still without a robust method for its proving. In 2012 Vallée and Dunham (2012) published a method that studied far-field waveforms from supershear earthquakes. They conclude that unilateral supershear ruptures have similar shape of surface waves on the border of Mach cone as surface waves of smaller earthquake with the similar mechanism and location. In this work we use their method and we developed a script in Python with use of ObsPy library. Our script is capable of downloading and processing data from worldwide seismic databases like IRIS. We tested our program on a supershear earthquake in 2001, Kokoxili, China, which was studied in the original paper. Our results were the same as the original one. Then we use our script to other potential supershear earthquakes: Denali 2002, Yushu 2010 and Aegean sea 2014 to test the method and its results. We conclude that this method is relatively stable for large earthquakes like Kokoxili where we have a big difference between the main shock and the small one. For smaller events there could be a problem with seismic noise and proper setting of frequention.
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Relative earthquake locations
Jeschkeová, Zuzana ; Bachura, Martin (advisor) ; Doubravová, Jana (referee)
This bachelor thesis concerns the issues related to techniques of earthquake locations. The methods can be divided into a two groups: absolute (Geiger method, grid search) and relative (master-event, hypoDD) ones. A greater emphasis is put on the latter ones - the relative methods. In these methods make use of so-called differential times - absolute time differences between phase arrivals of two earthquakes. The differential times can be estimated by the means of waveform cross-correlations. Our main objective was to compare cross-correlated differential times with the real ones and determine their accuracy. The analysis revealed that the difference - bias in differential time is present and for tho earthquakes with different magnitude it can reach 0.06 s. Keywords: locations, earthquakes, cross-correlation, seismograms
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Seismic activity measurement using fiber optic sensors
Vaněk, Stanislav ; Horváth, Tomáš (referee) ; Vojtěch, Josef (advisor)
The aim of master's thesis is to get familiarized with the problems of measurement and analysis of seismic waves. Theoretical part deals with the description of seismic waves, especially their types, sources and properties. Attention was afterwards focused on the measurement systems of these waves, emphasis was placed on their principles and advantages. The practical part discusses methods of noise reduction and highlighting of significant events in measured data. At the end, individual methods are implemented into user-friendly graphical interface.
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The source process of Greek earthquakes
Křížová, Dana ; Zahradník, Jiří (advisor) ; Málek, Jiří (referee) ; Šílený, Jan (referee)
Title: The source process of Greek earthquakes Author: Dana K ížová Department: Department of Geophysics Supervisor of the doctoral thesis: Prof. RNDr. Ji í Zahradník DrSc., Department of Geophysics Abstract: Investigations of moment tensor (MT) and its uncertainty are topical. This thesis is focused on isotropic component of three shallow earthquakes: Event A in Cretan Sea (Mw 5.3) and two events near Santorini island, B (Mw 4.9) and C (Mw 4.7). MT is inverted from full waveforms in an assumed 1D velocity model. The inverse problem is non-linear in centroid depth and time, and linear in six MT parameters, one is the MT-trace. Uncertainty of isotropic component is studied by a new approach (K ížová et al., 2013). The trace is systematically varied, and remaining parameters are optimized. The method reveals tradeoffs between the isotropic component, depth, time, and focal mechanism. From two existing velocity models, we prefer the one with lower condition number, in which a (positive) isotropic component is indicated for event B. To rapidly assess a likely existence of isotropic component, an empirical method is proposed (K ížová et al., 2016). It is based on comparison between depth- dependences of waveform correlation in full and deviatoric modes. Based on extensive synthetic tests, the method confirms a...
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