This paper presents results of the research on tectonic activity of the marginal sudetic fault (MSF). Velocities of points obtained from processing GPS observations in the GEOSUD network and results of national precise leveling networks have been analysed. Results of 1996-2005 GPS measurements and results of measurements of selected points for the 2006-2007 period were taken considered. The velocities calculated by means of the Bernese GPS Software 5.0 were used to test hypothesis on present-day strike-slip movement activity of the marginal sudetic fault. The relationship between the calculated velocities and the length of projection onto the fault’s line was studied. The second part contains analysis of relative vertical velocities of benchmarks, making up the 1st and the 2nd class national precise leveling lines crossing the fault line, to study its vertical activity. Velocities of horizontal and vertical changes of points on both sides of the fault were compared with models described in literature., Jan Kapłon and Stefan Cacoń., and Obsahuje bibliografii
The motion of Earth’s spin axis in space is monitored by Very Long-Baseline Interferometry (VLBI), and since 1994 also its rate is measured by Global Positioning System (GPS). From the direct analysis of the combined VLBI/GPS solution in the interval 1994.3-2004.6 we recently found that the apparent period of the Retrograde Free Core Nutation (RFCN) grew from original 435 days to 460 days during the past ten years, but the resonance effects yielded a stable period of about 430 days. Now we repeat the same study with VLBI-only data, covering much longer interval (1982.4 - 2005.6). Direct analysis shows again a substantial increase of the apparent period during the last decade or so. The resonant period is given by internal structure of the Earth (mainly by the flattening of the core), so it is highly improbable that it is so much variable. From the same observations we derive corrections of certain nutation terms. A subsequent study of indirect determination of resonance RFCN period from the observed forced nutation terms through the resonance effects proves that the natural resonance period remains stable and is equal to 430.32±0.07 solar days. From this follows that an excitation by outer layers of the Earth (atmospheric, oceanic) should exist, with a terrestrial frequency close to that of RFCN (of about -1.0050 cycles per solar day, i.e. with period of -23h53m mean solar time), invoking the apparent changes of the directly observed RFCN period. Thanks to a close proximity of the resonance, any excitation with this period is extremely amplified so that the excitation necessary to explain the difference can be very small. The atmosphere alone contains enough power to excite the observed changes., Jan Vondrák and Cyril Ron., and Obsahuje bibliografii
The results of geodetic GNSS measurements on the EYPA station (bult by INSU CNRS from France) in Corinth Gulf in Greece are analyzed. Data is analyzed in the time interval before and after the earthquakes, which occured in January 2010. Results confirm vertical and horizontal co-seismic shifts of EYPA station of the order of 4 cm and 1 cm., Jan Kostelecký and Jan Douša., and Obsahuje bibliografické odkazy
We present first results of the study of possible relations between the seismic activity and crustal fluids (groundwater an d carbon dioxide) in the area of the Hronov-Poříčí Fault Zone (HPFZ), situated on the NE margin of the Bohemian Massif. Local seismic monitoring and observations of groundwater levels in deep wells and concentrations of carbon-dioxide in the mineral spring at Třtice was started in 2005. Since then, more than 30 local seismic events were observed in the area of the HPFZ. The two strongest earthquakes with macroseismic effects were recorded on August 10, 2005 (M = 2.4) and October 25, 2005 (M = 3.3). Most of the epicentres were situated along the central part of the HPFZ. Only some weak events from February and March 2006 were concentrated along the SE termination of the HPFZ. Results of the hydrological monitoring show that water level fluctuations are affected mainly by the precipitation, snow-melt, air pressure changes, and tidal deformations of the Earth’s crust. The effects of seismo-tectonic activity were detected only in one out of five water wells, where we observed several step-like water level anomalies with amplitudes of 4 to 15 cm. Two of them preceded the August 10, 2005 and October 25, 2005 earthquakes. Three other anomalies seemed to originate independently of the seismic activity. We therefore suppose that they were induced by aseismic movements along the HPFZ. Contrary to the water level fluctuations, CO2 concentrations in the mineral spring seem to be dependent on water temperature; no evident seismic-induced changes have been observed yet., Vladimír Stejskal, Lumír Skalský and Ladislav Kašpárek., and Obsahuje bibliografické odkazy
The influence of mineralogical composition, electrical conductivity and pH on the rheological properties of Latvian illite clays has been investigated. Samples from two deposits have been studied. The average plasticity index of samples from both Laza deposits is 23-25, but from Apriki - around 20. Based on these results, 2 sample s with different plasticity indices from each borehole were chosen for further research. All suspensions exhibityield-pseudoplastic behavior. Samples with the highest amount of clay minerals have the highest plasticity index and apparent viscosity. From 3 samples with similar amount of clay minerals and plasticity index one sample has higher pH and electrical conductivity and therefore exhibits lower viscosity., Inga Dusenkova, Valentina Stepanova, Jana Vecstaudza, Vitalijs Lakevics, Juris Malers and Liga Berzina-Cimdina., and Obsahuje bibliografické odkazy
Ultrasonic velocity anisotropy in the rock provides information of variability of the dynamic elastic moduli. Young’s modulus and Poisson’s ratio calculated from waves velocities can be used to determine brittleness index, which is usually used to predict rock susceptibility for hydraulic fracturing. This paper describes laboratory ultrasonic measurements carried out in order to improve hydraulic fracturing designing. The research was conducted over two types of rock: shale and limestone. The samples were cut out perpendicularly and parallel to the bedding planes. Next they were tested for effective porosity and mineral composition using XRD method. Directionally depended seismic velocities revealed noticeable anisotropy of laminated shale, caused by orientation of the bedding planes and weak anisotropy of limestone. Based on the velocities, dynamic elastic moduli and its anisotropy coefficients were determined. Calculations of brittleness index based on Young’s modulus to Poisson’s ratio relation and three types of mineral composition brittleness indexes, revealed strong variability in brittleness for both kind of tested formations. These results show, that different types of brittleness indexes should be used complementary, to better describe fracability of the rock. and Moska Rafal, Kasza Piotr, Maslowski Mateusz.
Rock landforms in the Sokolský hřbet (ridge) and the adjacent Žulovská pahorkatina (hilly land) have been analysed through detailed field mapping at a scale of 1:10,000; subsequently the spatial distribution of these features was analysed using a DEM within a GIS framework. Particular attention was focused upon the shape of the rock landforms, their arrangement, the aspect of their walls, and their topographic position within the two adjacent geomorphological units. Rock landforms in the Sokolský hřbet include frost-riven cliffs, isolated residual rockforms, and blockfields in metamorphic rocks. In contrast, rock landforms in the Žulovská pahorkatina include rock steps and numerous tors exposed from the basal weathering surface. The Sokolský hřbet has been interpreted as a neotectonically uplifted mountainous region; the rock landforms described here are thought to have formed under periglacial conditions during cold periods in the Pleistocene, whilst the extensive granitoid block accumulations developed on marginal fault scarps are thought to result from the exposure of intensively disintegrated rocks due to uplift. Žulovská pahorkatina has been interpreted as a remodelled stripped etch surface, which has been twice glaciated during the Middle Pleistocene. The rock landforms in both units appear to be structurally and lithologically controlled; moreover, various shapes of granite rock landforms are controlled by various types of jointing and parting. The clear differences recognised in both the rock landforms and overall morphology reflects the considerable disparity associated with relief development between two adjacent morphostructural units; such variability provides evidence for a long polygenetic history within the entire study area., Petra Štěpančíková and Matt Rowberry., and Obsahuje bibliografii
Compact conical strain gauge probe for borehole over-coring rock massif stress measurement (CCBO), based on experiences of K. Sugavara and Y. Obara, has been developed in Institute of Geonics ASCR, v.v.i. from 2004. First generation of CCBO is equipped by simple electronic circuit which requires continuous communication with control computer in the course of measurement. Prototypes of this type probes are used for long term stress changes monitoring induced by longwall advancement in mine. Solving of continuous data communication through rotating drilling tool filled by wash water in course of over-coring is very difficult technical task, which is not possible to solve in terms of grant project. To avoid this problem a development of second generation of CCBO equipped by microprocessor and internal data logger was initialised. Simplified modification of CCBO is developed as a probe for long-term monitoring of rock massif stress changes (Compact Conical Ended Borehole Monitoring - CCBM). Design of both models probes, discussion of measurement errors and technique of sensitivity self-calibration is described., Jaromír Knejzlík, Zdeněk Rambouský, Kamil Souček and Lubomír Staš., and Obsahuje bibliografii
This article is concerned with seismicity in the region of West Bohemia - Vogtland after the Nový Kostel swarm of 2000. Seismicity during the period 2001 - 2006 is weak, though with several clusters of earthquakes; although these do not meet the criteria for a seismic swarm, their groupi ng in time and spacing along a line give an impression of tectonic disturbances and their behaviour in a period between swarms., Vladimír Nehybka and Radka Tilšarová., and Obsahuje bibliografické odkazy
An earthquake of magnitude M = 4.4, macroseismic intensity Io = 7 in the EMS scale, followed by a long series of aftershocks occurred on November 30, 2004 in southern margin of the Orawa-Nowy Targ Basin, Western Carpathians. Macroseismic epicentral data were determined for the main earthquake and the strongest aftershocks. The foci were shallow, less than 5 km i.e., originated in the Podhale Flysch. An array of seismic stations located in this seismically active area is necessary for better recognizing of the ongoing tectonic process., Barbara Guterch., and Obsahuje bibliografii