Parameters of finite seismic source model were determined for a set of 36 selected events of the West Bohemia 2000 earthquakes swarm (Ml from 1.7 to 3.0) using stopping phases method. Two stopping phases are generated along the source border where the rupture process terminates and these phases form Hilbert transform pair, which is also the criterion for their identification. Circular and e liptical source models were considered and corresponding source parameters were calculated by inverting interpreted stopping phases delays. As generalization of circular to elliptical model was found to be statistically insignificant, only results related to the circular source including error estimates are presented. Our results are in a good agreement with previously published theoretical formula concerning source radius and magnitude and also fairly well confirm general theoretical assumption about constant stress drop. The determined stress drop ranges between 1 - 10 MPa with the typical value of 2.4 MPa., Petr Kolář and Bohuslav Růžek., and Obsahuje bibliografické odkazy
Velká přírodní katastrofa z 26. 12. 2004 v jihovýchodní Asii si vyžádala 300 tisíc obětí na životech. Při zemětřesení magnituda 9, které silnými pohyby půdy zdevastovalo severní část Sumatry, vzniklo tsunami, které pak během několika následujících hodin zkázu dovršilo na pobřeží několika států v Bengálském zálivu i jinde. Má-li se lidstvo chránit před účinkem podobných katastrof, musí znát jejich tektonické příčiny, fyzikální mechanismus i společenské důsledky. Významným způsobem k tomuto širokému okruhu otázek přispívá seismologie., Jiří Zahradník, Jan Burjánek, František Gallovič., and Obsahuje seznam literatury
Long-term geotechnical monitoring of crack and fissure movements in slope deformations, historical buildings, as well as underground objects in Slovakia, provided results that bear evidence of movement trends, as well as of present tectonic unrest. The results were subject to an analysis regarding anomalies in movements that would verify activity of a specific geodynamic process. Such a process was detected recently in the Bohemian Massif and evidenced even in other European countries, north as well as south of the Alps. The process began by a tectonic pressure pulse and followed by a phase of increased geotectonic activity. The search for signs identifying this process on the Slovak territory which belongs to a different geological unit than the Bohemian Massif was successful. This is further evidence that the process in question is of a very deep foundation. The investigations proved successful long-term outdoor operation of TM71 crack gauges working on the principal of mechanical interference between optical grids. A thirty year long record was even reached. A useful function of the gauge which allows for supplementary data about angular deviations in faults has been found useful in the analysis. The data indicate affinity of the process to a large global disturbance in the Earth crust., Ľubomír Petro, Blahoslav Košťák, Josef Stemberk and Ján Vlčko., and Obsahuje bibliografii
The western part of the Bohemian Massif (Vogtland/West-Bohemia region at the Czech-German border) is characterized by relatively frequent intraplate earthquake swarms and by other manifestations of current geodynamic activity, such as mofettes, mineral and thermal springs. In this study we analyze variations of groundwater level in four hydrological wells in the region during the years 2005-2010. Monitoring during the previous time interval of 2000-2004 is also mentioned and used for comparison. Two of the wells are located in the epicentral region of Nový Kostel, and the other wells are more distant. The time interval includes the 2008 earthquake swarm when all the wells displayed a noticeable drop in the water level. This effect was observed up to epicentral distances of nearly 30 km, which exceeds the distances of hydrological changes observed during previous earthquake swarms. Moreover, it seems that a small rise in the water level preceded the intervals of increased seismic activity, which could represent a certain precursory phenomenon. On the other hand, the hydrological changes in the Nový Kostel area were relatively small, indicating that this epicentral area is not hydrologically linked with the seismically active fault at depth. Consequently, more suitable localities for hydrological monitoring should be sought in a broader vicinity of Nový Kostel., Renata Gaždová, Oldřich Novotný, Jiří Málek, Jan Valenta, Milan Brož and Petr Kolínský., and Obsahuje bibliografii
In the West Bohemian region, Central Europe, the volcanic activity appeared in late Tertiary, the Miocene. The present intraplate magmatic activity makes itself felt by flows of gaseous and liquid fluids, enhanced geodynamic mobility of geological structures and generation of earthquake swarms. Position data of two permanent Global Navigation Satellite Systems (GNSS) stations located in the region were used to calculate the time variations of the horizontal strain field that were compared with the 3He/4He ratios and earthquake swarm occurrences. The strains and 3He/4He ratios displayed a positive relation supported by the earlier opinions on the dependence of the dynamics of the region on the fluid occurrence. Analysis of these quantities observed in 2006-2007 period indicated when the compressions calmed and the 3He/4He ratios grew then the earthquake events occurred. It presumes the detected variations relate to compressions and extensions in the region. The strain field changes monitored during the 2008 swarm proved the relation found above. The observed connections could be applied in future at selected regions in earthquake forecast procedures., Vladimír Schenk and Zdenka Schenková., and Obsahuje bibliografii