a1_In cooperation with AIUB (Astronomical Institute University of Berne), GOP (Geodetic Observatory Pecný) and IGN (Institut Géographique National), DORIS data analysis capabilities were implemented into the development version 5.0 of the Bernese GPS Software. The DORIS observables are reformulated that they are similar to GNSS carrier phase observations as much as possible allowing the use of the same observation models and algorithms as for GNSS carrier phase data analysis with only minor modifications. Evolution of DORIS data analysis using Bernese GPS Software is presented from the pilot campaign (September 2004) to the automatic processing of multi-year data time-series. The station and pole coordinates were estimated within the free-network approach and the long time-series of weekly estimated parameters are presented (1993.0- 2009.0) and analyzed. The RMS of the estimated polar coordinates significantly decreased after 2002, when the second generation of DORIS satellites was launched. A significant improvement has been achieved by processing the data from the new satellites (SPOT-5 and Envisat) launched in 2002. The RMS in 2003-2009.0 shows the decreasing trend and reached values close to 0.4 mas in both coordinates (2007-2008). Behavior of the terrestrial reference frame scale was quite stable with a few exceptions. Analysis of the major scale shift at the end of 2004 revealed the SPOT-5 and Envisat satellites as the source of the problem. On the other hand, the termination of the TOPEX/Poseidon DORIS data processing at the end of 2004 did not influence significantly the overall scale level. Another goal of the paper is a detail analysis of relations between the value of the observation residuals and the length of the observation time-interval. A simple empirical model considering the observation noise as a sum of the constant and time-dependent terms is applied and discussed., a2_A significant DORIS-GNSS ZTD bias as well as station height bias have been detected in the case of the SPOT-5 data for South America stations Santiago, Cachoiera Paulista, and Arequipa. These stations are located in the area of the South Atlantic Anomaly (SAA)., Petr Štěpánek, Vratislav Filler, Urs Hugentobler and Jan Douša., and Obsahuje bibliografii
Microseismic monitoring has become a standard technique to map the development of hydraulic fracturing. This study is a case study of a downhole monitoring of the hydraulic fracturing in a lateral well in Northern Poland. The downhole monitoring array detected a large number of microseismic events indicating successful development of a hydraulic fracture. We show evidence that some stages interacted with the pre-existing natural fault system also mapped from surface active seismic imaging. The mapped hydraulic fracture shows a slight asymme try of the developed hydraulic fractures. We show that the observed microseismicity is cons istent with microseismicity usually observed in the North American shale gas stimulations., Eryk Święch, Paweł Wandycz, Leo Eisner, Andrzej Pasternacki and Tomasz Maćkowski., and Obsahuje bibliografické odkazy
In this study the compressive strength and durability of soft clay soil stabilized with halloysite nanotubes are investigated. Halloysite nanotubes are novel 1D natural nanomaterials which are widely used in reinforcing polymer, pollution remediation, and as nanoreactors for biocatalyst. The wide use of halloysite nanotubes is due to their high aspect ratio, appropriate mechanical strength, high thermal stability, nature-friendly and cost-effectiveness. However, the use of halloysite nanotubes as a stabilizing agent for improving the durability of soil is not clear. In this research, halloysite nanotubes was used in the amounts of 2%, 5% and 10% by the weight of dried soil. Unconfined compressive strength, wet/dry cycles and freeze/thaw cycles tests were performed to evaluate the strength and durability of stabilized soft clay soil. Experimental results showed that halloysite nanotubes considerably improves the compressive strength and durability of soft clay soil. The optimum amount of halloysite nanotubes for soil stabilizing in terms of compressive strength and durability was 5%. The compressive strength of soft clay increased as much as 129% by applying 5% halloysite nanotubes. Also, the specimen containing 5% halloysite nanotubes showed the least strength loss after wet/dry and freeze/thaw cycles. The soil sample containing 5% halloysite nanotubes lost 20% of its initial compressive strength after 8 cycles of freezing and thawing, while the soil sample without any halloysite content lost 100% of its compressive strength after the same number of freezing and thawing. Based on the obtained results, the use of halloysite nanotubes in order to enhance the strength and durability of soft clay is strongly recommended., Tavakolipour Masoud, Salemi Niloofar., and Obsahuje bibliografické odkazy
The long water-tube tiltmeter observations of the plumb line variations were begun about four years ago. Since 2001, twice, the instrument registered strong plumb line variations associated with earthquake. Earthquake in September 2003 made opportunity for verification of hydrodynamic system of tiltmeter. We obtained in observations large number of cycle-slip effects, which made impossible correct interpretation of data during main phase of phenomenon. Results of tests of dumping system of water waving helped us to introduce some improvements in hydrodynamic system of instrument. Catastrophic earthquake with magnitude 9.1 which took place in the area of Indian Ocean on 26th December 2004 generated phenomenon of the Earth free oscillations associated with anomalous plumb line variations of the order of single milliseconds of arc (mas). The effects of surface waves passing associated with Earth free oscillations were registered by the tiltmeter as series of anomalous plumb line variations. Surface waves produced several milliseconds of arc amplitude of plumb line variations. Results of observations showed that low-pass filters considerably reduce contribution of short-period effects and effectively protect hydrodynamic system of instrument against resonance. Nevertheless during first two hours of phenomenon cycle-slip effects occurred several times. Plot of plumb line variations in space from 26th December 2004 showed us large complication of tilt signals as well as dominated role of tidal signal. Spectral analysis of the time series of the plumb line variations obtained with help of the long water-tube tiltmeter on 26 December 2004 appeared existing fundamental modes (n = 0) in the Earth free oscillations didn’t exceed 0.2 mas., Marek Kaczorowski., and Obsahuje bibliografii
The orientation of the Earth in space is measured by space geodetic techniques. Each technique has its weaknesses so the best way how to get a representative solution of Earth orientation parameters is to combine all of them together using some appropriate method. There are basically two approaches, the rigorous and non-rigorous one. The method used in this paper belongs to the second category. Since 1999, when the authors Kostelecký and Pešek put basis of the combination method, the method has been modified and improved. The particular improvements are described hereafter and recent results are presented. These results of collocation station velocities are compared with the velocities published by ITRF 2005 and NUVEL-1A. The mean values of differences are 2.7 mm/y and 5.9 mm/y, respectively., Vojtěch Štefka, Ivan Pešek, Jan Vondrák and Jan Kostelecký., and Obsahuje bibliografii
Recently we derived a new star catalog EOC-4 that contains not only the mean positions and linear proper motions, but also periodic changes, due to orbital motions, for double and multiple star systems. The catalog contains 4418 stars that were observed in programs monitoring Earth orientation by optical astrometry during the 20th century. 599 stars of the catalog have significant periodic components. This catalog is now used, as a basic celestial frame, to obtain the Earth orientation parameters from optical astrometric observations of latitude/universal time/altitude in the interval 1899.7-1992.0. Polar motion is determined in 5-day steps for the whole interval studied, Universal time covers the interval 1956.0-1992.0 (i.e., after the invention of atomic clocks) also in 5-day steps, and celestial pole offsets (with respect to recent IAU2000 and IAU2006 models of nutation and precession) are modeled by second-order polynomials of time. In addition to these, a combination of Love and Shida numbers for each observing site is computed., Jan Vondrák, Cyril Ron and Vojtěch Štefka., and Obsahuje bibliografii
The use of rock physics modeling and petrophysical analysis has become an integral part of quantitative seismic interpretation. In the present study, the above-mentioned techniques are applied to the reservoir interval of Basal Sand of Cretaceous age widely distributed in the Lower Indus Basin of Pakistan. The data used for this purpose consists of complete suits of wireline logs from four well A, B, C and D. The primary goal of this work is to understand the trends of seismic parameters such as P-wave velocity (VP), S-wave velocity (VS), bulk modulus, bulk density as a function of fluid saturation and porosity in this sand interval. Petrophysical analysis based on well logs is used to obtain petrophysical properties such as porosity, the volume of shale, fluid saturation, P-wave velocity (VP), S-wave velocity (VS) and density at reservoir conditions. The results show that seismic parameters are very sensitive to fluid saturation, fluid types and rock-forming sediments. Reservoir porosity and fluid saturation control the elastic response of Basal Sand due to which seismic velocities decrease with an increase in porosity and fluid saturation., Perveiz Khalid, Muhammad Arshad, Muhammad Irfan Ehsan, Aziz Ahmad and Shehzad Khurrum., and Obsahuje bibliografii
A good knowledge of hydraulic characteristics, particularly the retention curves, of the applied materials is necessary when studying the efficiency of a capillary barrier or numerically simulating flow of water in its layers. The main difficulties of their measurements originate in the fact that the coarse-grained soils of capillary barriers come from the state of residual moisture to the state of saturation within relatively small interval of pressure head. Hence, it is necessary to carry out the measurements in very fine steps of pressure head. Four materials of two capillary barriers are investigated in this paper. The tension apparatus according to Havlíček and Myslivec was used to measure their retention curves. Both branches of retention curves were measured in order to obtain data suitable for taking hysteresis into account. The method is described and the results are presented. Subsequently, the hydraulic characteristics of the materials are determined and their impact to the capillary barriers efficiency is investigated. The barriers were compared from the viewpoint of their efficiency using the measured data and tipping trough measurements made elsewhere. Explanation of the found differences was suggested and the effect of hysteresis was discussed., Dagmar Trpkošová and Jiří Mls., and Obsahuje bibliografii
We study the efficiency of individual stations of the CRL seismic network in recording the seismic activity in the western Gulf of Corinth, Greece. The stations are located on both the northern and southern coast of the Gulf. The study is based on 5027 earthquakes recorded in 2001, separated into three groups, the southern, central and the northern one. The events were located using the HYPO71PC algorithm. It is shown that the stations significantly differ in their monitoring ability., Jaromír Janský, Jiří Zahradník and Vladimír Plicka., and Obsahuje bibliografii