Celestial pole offsets are the displacements between the observed position of the Earth’s spin axis in space and its position predicted by the adopted models of precession and nutation. At present, the models are IAU2006 and IAU 2000, respectively. The celestial pole offsets are regularly measured by Very Long-Baseline Interferometry (VLBI), the observations being coordinated and published by the International VLBI Service for Geodesy and Astrometry (IVS). These offsets contain a mixture of several effects: the unpredictable free term, Free Core Nutation (FCN) that is due to the presence of the outer fluid core of the Earth, forced motions excited by the motions in the atmosphere and oceans, and also imperfections of the adopted precession-nutation models. The geophysical excitations are also available, as determined by several atmospheric and oceanographic services. The aim of this paper is to compare the time series of these integrated excitations with the observed celestial pole offsets and estimate the level of coherence between them., Cyril Ron and Jan Vondrák., and Obsahuje bibliografii
The combination method of results of different space geodetic techniques gives two kinds of products. On the one hand, the Earth orientation parameters (EOP) that define the orientation of the Earth in space and, on the other, the coordinates of collocation stations by them the ITRF is realized. Obtained results are based on the method developed by authors, so called “non-rigorous” combination of the data. Approximately eight-year data was successively processed in order to obtain solutions of both products, which were then compared with the results given in ITRF 2005 solution., Vojtěch Štefka, Jan Kostelecký, and Ivan Pešek., and Obsahuje bibliografii
P-wave velocity anisotropy of rocks is often investigated by laboratory methods. The extrapolation of the laboratory results to larger rock units requires comparison with direct field measurements. Physical properties of deep-originated rocks were performed on mantle-derived peridotite from the Ivrea zone (N orthwestern Italy). These rock s were exhumed by tectonic processes during collision orogeny up to the Earth’s surface. The direct surface seismic measurements of elastic waves velocity were realized by means of shallow seismic refraction method on the outcrop of peridotite. The measuring base was about 10 m long. Laboratory seismic anisotropy measurement was realized on rock samples from the same outcrop. The geographically oriented spherical samples with diameter 50 mm were radiated by elastic waves in 132 directions under confining stress from atmospheric level up to 200 MPa. Laboratory and field values of the anisotropy of seismic wave ve locities were compared and different scales of measurements were evaluated. The field measuremen ts used frequency about 1 kHz whereas the laboratory measur ement used 700 kHz radiation. Field measurements proved relatively high value of anisotropy P-wave propagation - 25%, while laboratory experiments only 1.5%. This difference is caused by different reason of anisotropy. Laboratory samples contain only microcraks, which represents nearly continuum with rega rd to ultrasound wave length (11 mm). Rock massif, however, contains beside mickrocraks also cracks with comparable size of applied seismic wave length (10 m)., Jan Vilhelm, Vladimír Rudajev, Roman Živor, Tomáš Lokajíček and Zdeněk Pros., and Obsahuje bibliografické odkazy
This paper discusses the quality of slant wet delays (SWD) computed from GPS measurements. The SWDs are generally used as input data for GPS tomography, which allows the three-dimensional reconstruction of water vapour distribution in the atmosphere. The research presented is based on a comparison of slant wet delays acquired by different strategies based on double-differenced Global Positioning System (GPS) data. The GPS-derived SWDs were compared with those directly measured by a water vapour radiometer (W VR). The best results from the applied G PS strategies were achieved by a simple mapping of GPS-derived zenith total delays into SWD without adding horizontal gradients or post-fit residuals., Michal Kačmařík, Jan Douša and Jan Zapletal., and Obsahuje bibliografické odkazy
Sandstones have been widely used as a building material since the medieval time all around the Europe. Porosity is one of the main factors affecting the resistance to weathering processes and consequently to the changes of mechanical and physical properties of these stones. Rock material is generally negatively influenced especially during the winter period when frost action takes place. Effect of salt crystals and ice formation depends on the character of pore space, including the pore size distribution. Mercury porosimetry is well known method which provides information about porosity and pore size distribution of samples, but as any other method, it has its own limitations. X-ray microtomography can be used as a complementary method enabling another "view" into the pore space. Main aim of this paper has been to provide the information about the use of these two mentioned methods and comparison of obtained results, within the study of sandstone weathering. The research was focused on two commonly used Czech Cretaceous sandstones - Hořice and Božanov. The stones were exposed to the accelerated durability test which is based on the meteorological data measured in Prague winters from 1998 to 2008. There were described the changes in the area of pores diameters > 5 μm. Use of mercury porosimetry together with X-ray microtomgraphy enabled more detailed understanding of the processes inside the stone structure., Kateřina Kovářová, Robert Ševčík and Zuzana Weishauptová., and Obsahuje bibliografické odkazy
This paper reports an investigation into the composition of gypsum from Kobeřice locality (Czech Republic). The X-ray diffraction along with FTIR spectroscopy and thermal analysis show that almost pure gypsum occurs mainly in autochthonous horizons. While allochthonous clastic deposition is represented by gypsum containing also calcite, quartz, clay minerals and organic matter., Pavel Konečný, Eva Plevová, Lenka Vaculíková, Alena Kožušníková, Janka Peterková and Marianna Hundáková., and Obsahuje bibliografii
Since October 2011, the Russian GLObal NAvigation Satellite System (GLONASS) has been revitalized and is now fully operational with 24 satellites in orbit. It is critical to assess the benefits and problems of using GLONASS observations (i.e. GLONASS-only or combined Global Positioning System (GPS) and GLONASS) for precise positioning and zenith total delay (ZTD) retrieval on a global scale using precise point positioning (PPP) technique. In this contribution, extensive evaluations are conducted with Global Navigation Satellite System (GNSS) data sets collected from 251 globally distributed stations of the International GNSS Service (IGS) network in July 2016. The stations are divided into 30 groups by antenna/radome types to investigate whether there are ante nna/radome-dependent biases in position and ZTD derived from GLONASS-only PPP. The positioning results do not show obvious antenna/radome-dependent biases except the stations with JAV_RINGANT_G3T/NONE. For these stations, the averaged biases in horizontal component, especially in the north component, can achieve as high as -9.0 mm. The standard de viation (STD) and root mean square (RMS) are used as indicators of positioning repeatability and accuracy, respectively. The averaged horizontal STD and RMS of GLONASS-only PPP are comparable to GPS-only PPP, while in vertical component, those for GLONASS-only P PP are larger. Furthermore, the STD and RMS of GPS+GLONASS combined PPP solutions are the smallest in horizontal and vertical components, indicating that adding GLONASS observations can achieve better positioning performance than GPS-only PPP. With the IGS final ZTD as reference, we find that ZTD biases and accuracy of GLONASS-only are latitude - and antenna/radome-independent. The ZTD accuracy of GLONASS-only PPP is slightly worse than that of GPS-only PPP. Compared with GPS-only PPP, the ZTD accuracy is only improved by 1.3% from 7.8 to 7.7 mm by adding GLONASS observations., Feng Zhou, Shengfeng Gu, Wen Chen and Danan Dong., and Obsahuje bibliografické odkazy
Clays (2005) and the Handbook of Clay Science (2006) are new textbooks. Clays, written by Alain Meunier, is for those studying earth sciences. The Handbook of Clay Science, edited by Faїza Bergaya, Benny Theng and Gerhard Lagaly, is concerned particularly with the industrial application of clay mineral science. Both books ar e timely and could fill important gaps in the library of mineral science. Their quality as textbooks is discussed. Critical an alysis of editorial accuracy, indexes and user-friendliness indic ate that both books fall short of the high standards that should be the hallmark of academic publication. Their shortcomings seem to be related to widespread problems that may beset commercial publica tion of scientific books., Christopher V. Jeans., and Obsahuje bibliografické odkazy
The paper presents selected results of seismological observations in Silesia and northern Moravia between 01/2004 - 08/2008, which are based on interpretation of three-component digital recordings at solitary seismic stations operated by the Institute of Geonics of the ASCR Ostrava (IGN) distributed in the region under investigation. Five seismic stations had recorded local tectonic seismic events in a continuous regime until 12/2005, when the grant project GA CR No. 205/03/0999 terminated. Meanwhile, the Ostrava - Krásné Pole (OKC) seismic station have continued in operation as a part of the Czech regional seismological network since 1983 up to present. Other three stations have been operating in a so-called triggered regime. At the mid-January 2007, seismic station in Klokočov village was re-opened in continuous regime. During 55 months of observation, 90 tectonic events have been detected at one or more seismic stations mentioned above. However, database of the Institute of Physics of the Earth of the MU contains more than 640 microearthquakes during the same time. This discrepancy is caused mainly due to a higher concentration of microearthquake foci distributed all over the western part of the region under investigation where the IPE seismic stations are situated. On the other hand, the IGN seismic stations are spread predominantly within the eastern part of the territory, i.e. relatively far from the recent foci, and moreover, some stations are operated using the triggered regime., Karel Holub, Zdeněk Kaláb, Jaromír Knejzlík and Jana Rušajová., and Obsahuje bibliografii
Experimental geomechanical and seismological measurements are performed in the medieval Jeroným Mine near Čistá (Sokolov district). The main aim of this activity is geomech anical stability evaluation of this monument. Periodical monitoring was started in 2001 whereas quarterly period was applied (measurement of crack development in the mine working, development in changes in convergence cross-sections of linear and spatial workings and fluctuations of water levels in underground spaces). Seismological monitoring was started during reconstruction of partly impassable drainage adit. At present, selected parts of described geomechanical system are newly instrumented to obtain continuous information. Data obtained from periodical and continuous monitoring are presented in this contribution. Interpretation of seismological data on both natural and technical seismicity and fluctuations of water levels is presented in details., Zdeněk Kaláb, Jaromír Knejzlík, Robert Kořínek, Radovan Kukutsch, Markéta Lednická and Petr Žůrek., and Obsahuje bibliografické odkazy