Best-fitting tri-axial earth ellipsoid parameters derived from satellite observations

Résumé De l'ensemble des coefficients harmoniques du développement du géopotentiel [3, 6, 7], calculé à partir des variations des éléments orbitaux des satellites, on a calculé les paramètres de l'ellipso?de terrestre triaxial, représentant la surface du géo?de. La solution fut effectuée par méthode analytique sous la condition du minimum de l'intégrale du carré de l'écart du rayon vecteur du géo?de et de l'ellipso?de, de même que par calcul numérique à partir des valeurs discrètes 10°×10°.

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Address: Politickych vězňů 12, Praha 1-Nové Město.     

Groundwater management by riverbank filtration and an infiltration channel: the case of Obrenovac, Serbia

The Vi? Bare groundwater source is used to supply water to the population and industry of Obrenovac, one of the municipalities of Belgrade (the capital of Serbia). It is a typical riverbank filtration site; exploitation is performed through 30 drilled wells and two radial wells located in the meander of the Sava River. The established hydraulic connection between the river and tapped aquifer is so great that the river regime has a dominant influence on the aquifer. As a consequence of this, water-delivery reduction occurs in the dry months (summer–autumn), when the population needs water the most. Based on the data associated with the river’s gauges, precipitation, quantity of pumped water and groundwater-level fluctuation, a simulation of the groundwater regime for non-steady-state flow conditions has been undertaken through a numerical model. To overcome problems of water shortage during the dry season, the possibility of artificial recharge using an infiltration channel, made up of two connected parts, was analyzed. During the dry months, 80 % of the wells receive water partly from the infiltration channel. In this way, possibilities for extracting additional water are created. The application of this concept is discussed.     

Determination of ecological significance based on geostatistical assessment: a case study from the Slovak Natura 2000 protected area

The Sitno Natura 2000 Site covers an area of 935,56 hectares. The Sitno region is significant due to the number of rare and endangered species of plants, and as a result is considered a location of great importance to the maintenance of floral gene pools. The study area suffers human impacts in the form of tourism. The main purpose of this study is to the measure landscape elements, determine the ecological significance of habitats within the Sitno area, and from this data, organize the study area into conservation zones. The results of this landscape quantification are numerical values that can be used to interpret the quality of ongoing ecological processes within individual landscape types. Interpretation of this quantified data can be used to determine the ecological significance of landscapes in other study areas. This research examines the habitats of Natura 2000 Sites by a set of landscape metrics for habitat area, size, density, and shape, such as Number of patches (NP), Patch density (PD), Mean patch size (MPS), Patch size standard deviation (PSSD) and Mean shape index (MSI). The classification of land cover patches is based on the Annex Code system.     

Chemical and structural relations of epitaxial xenotime and zircon substratum in sedimentary and hydrothermal environments: a TEM study

Xenotime overgrowths on detrital zircon in siliciclastic sediments have been reported in numerous studies. However, in natural samples, solid solution of zircon and xenotime is limited to near-end-member compositions. In order to characterize the interface region between both minerals and to draw inferences on the growth mechanisms of authigenic xenotime, we studied xenotime overgrowths on detrital zircon grains from two Phanerozoic sandstone samples with contrasting post-depositional histories. In one sample, the small (≤10 μm), pyramidal xenotime overgrowths are of diagenetic origin and grew without major discontinuity on the detrital zircon grain. The second sample shows up to >50-μm-wide, porous and inclusion-rich, hydrothermal xenotime overgrowths on detrital zircon, whereas the transition zone between both minerals is accompanied by large pore volume. Chemical compositions of the xenotime precipitates from the two samples differ particularly in Y, REE, Th and Sc concentrations, whereas high MREE availability in the diagenetic sample and the presence of Sc in the hydrothermal sample, respectively, appear to have promoted xenotime growth. Transmission electron microscopy on electron-transparent foils cut from the interface region shows that both the diagenetic xenotime and the hydrothermal xenotime are crystalline and grew in optical and crystallographic continuity to their detrital zircon substrata. Only a narrow transition zone (≤90 nm—diagenetic sample, 200–300 nm—hydrothermal sample) between zircon and xenotime is in part made up of nanometre-scale crystalline domains that are slightly distorted and may have formed from dissolution–re-precipitation processes at the zircon rim along with precipitation from the respective fluid.     

Equivalent-linear site response analysis on the site of the historical Trakošćan Castle,Croatia, using HVSR method

This paper presents a major extension of seismic vulnerability research project on the site of Trako??an Castle based on the initial horizontal-to-vertical-spectral-ratio (HVSR) results from Stanko et al. (2016). The estimated HVSR site frequencies and HV amplification at Trako??an Castle can only be used as an indication of the initial soil site frequency and amplification, so-called natural soil model, corresponding to the subsoil profile without the influence of an earthquake. The equivalent-linear (EQL) site response analysis has been carried out for different earthquake scenarios for a maximum input rock peak ground acceleration (PGA_ROCK) that corresponds to return periods of 95 (0.08 g), 475 (0.18 g) and 1000 years (0.31 g). The aim of the research is to evaluate structural seismic design responses and to determine type and degree of damage caused by local site effect, which is the result of an alluvial basin and topographic influences. The main objective of this research is the formation of local microseismic zones based on an EQL analysis: surface spectral acceleration and amplification maps at the predominant frequency. Based on the HVSR frequency response of the core structure of Trako??an Castle and the Tower itself (fundamental and higher frequency modes), maps of surface spectral acceleration and soil amplification at different frequencies (3, 5 and 10 Hz) are developed for different input PGA_ROCK levels (0.08, 0.18 and 0.31 g) to evaluate seismic response of the Castle. Observed amplifications are correlated with ground motion polarization and directionality of the ground motion from the alluvial basin to the hilltop. Shortening of predominant frequencies (lengthening of the period), particularly in the alluvial basin, has been observed with higher input PGA_ROCK in the EQL analysis. This effect is not manifested in the Trako??an hill, and predominant frequencies match HVSR frequencies. The use of certain geophysical survey methods at historical sites is a big problem, because terrain features (e.g. steep hills, mountains, ridges, slopes, cliffs) create lack of space and make it impossible to carry out geophysical investigation. Microtremor measurements at historical sites can overcome this limitation and provide local seismic response and vulnerability behaviour of historical monuments without destroying their authenticity. Also, computational modelling can greatly improve the results. The EQL site response analysis on the site of Trako??an Castle has confirmed and improved the results of seismic response and vulnerability based on HVSR method.