The Institute of the Rock Structure and Mechanics AS CR operates the GEONAS network that now consists of 17 perm anent GPS observatories. The outliers and in consistencies occur within the time series observed in the winter season 200 5/2006 for the position of the GNSS antennas of the observatories SNEC and BISK located high in the m ountains, at th e Sněžka Mt. (1602 m, the Giant Mts.) and the Biskupská kupa Mt. (890 m, the Jeseníky Mts.) respectively. Therefore web cameras and meteorological sensors were in stalled at GEONAS observatories located in the mountain regions. The snow coverage and other meteorological influences affecti ng the antennas monitoring GPS signals at these observatories were estimated. The individual photos were analyzed and compared to variations in the time series to obtain the time series for winter seasons reducing the snow coverage effects., Milada Grácová, František Mantlík, Vladimír Schenk and Zdeňka Schenková., and Obsahuje bibliografické odkazy
The essential point for seismological observation in the northern part of Moravia, Czech Republic, is a permanent seismic station Ostrava - Krásné Pole (OKC) that is a part of the Czech regional seismological network (hereafter CRSN). Institute o f Geonics AS CR, v.v.i., has also operated temporary seismic stations in this region since 1997. Current seismological stations are located in an abandoned mine working located in Zlaté Hory and in cellars in Klokočov and castle Raduň near Opava. The natural seismicity is after the swarm of microearthquakes in the vicinity of Opava in 1993 very low now. In region under discussion, seismic manifestations generated by mining induced seismicity in Upper Silesian Coal Basin (both Karviná an d Polish parts) and in Legnica-Głogów Copper District (LGOM) are also detected. Significant part of observations in this region is made by the Institute of Physics of the Earth (hereafter IPE), Masaryk University Brno, and about 1000 microearthquakes have been detected during the last ten years with maximum local magnitude up to 1.9., Zdeněk Kaláb, Jaromír Knejzlík and Karel Holub., and Obsahuje bibliografické odkazy
The article deals with estimating deformation between the African and the Eurasian Plate in the Eastern Mediterranean on the basis of GPS coordinate time series. Two sources of velocities were used for processing. The first was the freely available site velocities from the European Permanent Network (EPN). The second was the Egyptian GPS permanent network velocities. Their values were determined by the following technique. Firstly, the Egyptian site coordinates were computed from GPS daily observations, using the fiducial EPN stations. The daily site coordinates at a given time interval result in coordinate time series, which were analysed and used on velocity estimation of the Egyptian stations. Then the apparatus of the mechanics of continuum was applied to all resultant velocities. The regions of possible mutual interactions between the Eurasian and the African Plate in the Eastern Mediterranean were detected. The basic idea of this contribution is the common processing of GPS daily measurements from the Egyptian permanent network together with the EPN data. The available Egyptian GPS data cover almost the last three years, which represents a sufficient time interval for velocity estimation. Introducing the Egyptian permanent GPS measurements into processing enables a better estimate of deformations in the Eastern Mediterranean., Antonín Zeman, Khalil Hassan, Jan Holešovský, Abdel Monem S. Mohamed, Zbyněk Novotný, Mahmoud M. Salah, Jan Kostelecký and Radwan M. Ali., and Obsahuje bibliografii
Brown coal open pit mining in the basin under Krušné Hory Mts. came to contact with slopes of the mountains, and a problem of the stability in high and steep slopes in the crystalline rock became an important question. The question concerns Jezeří Castle built on the top of one of the hills in a most endangered section where even a supporting pillar in the sediments under the slope toe was left to support the slope. As a result, an extensive monitoring program regarding deformations was initiated in the region. The program involved several methods and some important results are discussed. The results that are displayed concern mainly measurements done in geophysical tiltmeter stations in two underground galleries driven into the two steep slope sections showing most dangerous situation, as well as extensometers located in the same locations. Long-term monitoring revealed a tectonic deformation process of a natural origin that is registered as slow and systematic tilts. Besides, it revealed several periods of anomalies that are of basic importance. During a long period of observation from 1982 till 2005 three important deformation anomalies were registered: the event of 1994, the event of 2002, and the event of 2003/2004. The first and the third event have been classified as of a large regional character that affected a wide mountainous area and could be interpreted as a tectonic impulse originating within the mountainous structure of the so called "Dome of Hora Svaté Kateřiny". The second event has been considered different, strictly connected with extreme precipitation of August 2002. The anomaly was evidenced even deep in the crystalline, so that it could not be seen as of a superficial character only. The movement which was registered at that time was oriented right into the pillar supporting the slope., It is concluded that it was a short manifestation of instability in the critical profile "Jezeří - pillar", which stresses the important stabilisation function of the supporting pillar without which the profile will be probably destabilised., Blahoslav Košťák, Bohumil Chán and Jan Rybář., and Obsahuje bibliografii
a2_The town of Litija was hit by four damaging earthquakes in the last 120 years which reached a maximum intensity of VII-VIII MSK. The town is located in a shallow sedimentary basin filled with relatively soft Quaternary sediments in which seismic site amplification is expected. On the other hand no borehole or geophysical data are available to support quantitative assessment of site effects. As a contribution to the first seismic microzonation of the area, we performed a free-field study based on the microtremor HVSR method in order to assess the resonance frequency of th e sediments. In ge neral clear spectral peaks were obtained for 57 measuring points which show distribution of frequencies in a broad range between 4.4 an d 22.7 Hz. The iso-frequency map was prepared by using natural neighbour interpolation algorithm. For soil-structure resonance assessment we considered large building stock from different Slovenian towns, because the building typology is similar in wider area. Low-rise masonry family houses with two or three floors prev ail. By microtremor measurements inside 45 such buildings their fundamental longitudinal and transver se frequencies were determined and statistically analysed in a complementary study. To assess the possible occurrence of soil-structure resonance in general, the average fundamental frequency +/- one standard devia tion interval is obtained for these two building heights, which give s the range 5.6-11.1 Hz. The free-field microtremor data shows that this frequency range occupies 37% of the urban area in the Litija basin. This study has shown that soil-structure resonance issue for low-rise buildings is frequently overlooked, but should be considere d seriously in shallow sedimentary basins, characterized by relatively high free-field frequencies, because many towns are located in such geological environment., a2_Second application of the derived iso-frequency map is to support soil classification, because recent investigations have shown that fundamental frequency of sediments can be used together with the average shear velocity in the upper 30 m to improve classi fications according to di fferent seismic codes., Andrej Gosar., and Obsahuje bibliografické odkazy