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National Repository of Grey Literature 2 records found  Search took 0.00 seconds. 
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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Polarization analysis of strong ground motions recorded during the aftershock sequence of the 2009 L'Aquila earthquake
 Čejka, František ; Gallovič, František (advisor) ; Zahradník, Jiří (referee)
During broadband modelling of selected events from the aftershock sequence of the l'Aquila earthquake using 1-D model of media, we observe interesting difference between model and real particle polarization on high frequencies. There are two basic types of these polarization disorders. Polarization of particle motion keeps its linear form, but changes its direction or linear polarization changes its linear form to circle polarization. It offers the explanation that these disorders of polarization occur due to the 3D heterogeneities in the crust. In this work, we analyze polarization of published synthetic seismograms modeled with random 3D heterogenitites. It has been shown that the biggest disorders occur in directions in which parcticle movement heads toward the source, and that we can find examples, which qualitatively explain observed polarization disorders.
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