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Simulation of the 2016 Tottori (Mw 6.1) earthquake using a dynamic source model
Hronek, Martin ; Gallovič, František (advisor) ; Premus, Jan (referee)
We perform a parametric study for simple elliptical dynamic models of rupture propa- gation. We simulate the earthquake from the central part of Japanese prefecture Tottori in 2016 using a code for a simulation of the rupture propagation developed at the Depart- ment of Geophysics assuming the classic linear slip-weakening friction law. We evaluate the match of synthetic seismograms with the observed data. From different models we choose the one best fitting the data. The values of seismic moment, slip distribution, stress drop, radiated energy and radiation efficiency are close to the ones from published articles. In conclusion we point out some possible sources of inaccuracies in modelling and suggest improvements for the future. 1
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Joint inverse modeling of coseismic and postseismic slip of the 2014 South Napa, California, earthquake
Premus, Jan ; Gallovič, František (advisor) ; Burjánek, Jan (referee) ; Tinti, Elisa (referee)
Title: Joint inverse modeling of coseismic and postseismic slip of the 2014 South Napa, California, earthquake Author: Jan Premus Department: Department of Geophysics Supervisor: prof. František Gallovič, Department of Geophysics Abstract: Slip at tectonic faults spans a wide range of time scales, from tens of seconds of earthquake coseismic rupture to months of aseismic afterslip, recorded in seismograms and geodetic data. The two slip phenomena are often studied separately, focusing on kinematic aspects. We introduce a Bayesian method for physics-based joint inverse modeling of an earthquake slip and afterslip, employ- ing a unifying rate-and-state friction law. To simulate the rupture propagation, we develop an efficient finite-difference open-source code FD3D TSN. GPU ac- celeration of the code yields speed-up by a factor of 10 with respect to a CPU, enabling hundreds of thousands of earthquake simulations in a reasonable time. We also implement a quasi-dynamic afterslip simulation using a boundary inte- gral element method. We apply the Bayesian dynamic inversion to the 2014 Mw 6.0 Napa earthquake. We reveal the dynamics of coseismic and postseismic slip in terms of stress and friction in a unified model, reconciling previous disjunctive analyses of the event. We show that the two types of slip are mostly...
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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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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 tensors of the largest events of the 2016 Central Italy earthquake sequence
Labuta, Martin ; Gallovič, František (advisor) ; Adamová, Petra (referee)
Title: Moment tensors of the largest events of the 2016 Central Italy earthquake sequence Author: Martin Labuta Department: Institute of Hydrogeology, Engineering Geology and Applied Geophysics Supervisor: doc. RNDr. František Gallovič, Ph.D., Department of Geophysics, Faculty of Mathematics and Physics, Charles University Abstract: Central Italy was stuck by an earthquake sequence in 2016, with the largest earthquake of moment magnitude Mw 6.5. 300 people have died after the first earthquake on August 24th, Mw 6.1 and the city Amatrice was heavily damaged. Utilizing the software ISOLA, the low-frequency centroids are found of selected earthquakes with Mw above 4.5. Using these results, the multiple point finite seismic sources are obtained in order to determine fault irregularities. Afterwards, there is a comparison of these results with other academic papers and earthquake catalogs. Keywords: earthquake, ISOLA, moment tensor, centroid
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Three-dimensional ambient noise tomography of the Bohemian Massif
Valentová, Ľubica ; Gallovič, František (advisor) ; Burjánek, Jan (referee) ; Kristek, Jozef (referee)
We have performed 3D ambient noise tomography of the Bohemian Massif. We invert adopted inter-station dispersion curves of both Love and Rayleigh waves in periods 4-20 s, which were extracted from ambient noise cross-correlations, using a two-step approach. In the first step, the inter-station dispersion curves are localized for each period into the so-called dispersion maps. To account for finite-frequency effects, gradient method employing Fréchet kernels is used. Assuming membrane wave approximation of the surface wave propagation at each period, the kernels were calculated using the adjoint method. To reduce the effect of data noise, the kernels were regularized by Gaussian smoothing. The proper level of regularization is assessed on synthetic tests. In the second step, the phase-velocity dispersion maps are inverted into a 3D S-wave velocity model using the Bayesian approach. The posterior probability density function describing the solution is sampled by more than one million models obtained by Monte-Carlo approach (parallel tempering). The calculated variance of the model shows that the well resolved part corresponds to the upper crust (i.e., upper 20 km). The mean velocity model contains mainly large scale structures that show good correlation with the main geologic domains of the Bohemian...
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Dynamic models of the earthquake source
Kostka, Filip ; Gallovič, František (advisor) ; Burjánek, Jan (referee) ; Kaneko, Yoshihiro (referee)
Dynamic models of the earthquake source allow simulating the evolution of stress and slip at tectonic faults by coupling the equations of motion in a volume surrounding the fault with a constitutive law that represents the surface forces acting on the fault. In the first part of the thesis, we review important properties of shear rupture for brittle, linear slip-weakening, and rate-and-state constitutive laws. In the second part of the thesis, we present two studies utilizing 3-D dynamic modeling at both long (hundreds of years) and short (seconds) time scales. In the first study, we model seismic cycles using the rate- and-state laws of friction and perform a parametric exploration of the effects of sudden intra-cycle shear stress perturbations on the clock advance or delay of the subsequent large event. We find that when the perturbation is applied during specific time intervals, the earthquakes following the perturbation are only small ruptures that do not completely release stress on the whole fault. The time interval between large earthquakes may thus be prolonged up to 80% when compared to the unperturbed cycles. We reproduce this behavior on a numerical heterogeneous model of the Parkfield segment of the San Andreas fault and demonstrate that the mechanism could have been responsible for the observed large...
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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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