The first satellite laser ranging at ondřejov observatory     

Petr Lála  Miroslav Prokeš  Reviewer M. Burša 《Studia Geophysica et Geodaetica》1976,20(4):391-395

Summary The first laser ranging of the satellites Geos A and B performed at Station 1148 Ondejov in 1972–1975 are evaluated. The least-squares method was used to estimate their internal accuracy. Polynomials of the 6th to 8th degree were found to be necessary for the best fit of a typical satellite pass. The root mean square error is always smaller than 20 ns (3 m), which is consistent with the expected accuracy of the laser ranging system.Dedicated to Prof. RNDr. Emil Buchar, DrSc., Corresponding Member of the Czechoslovak Academy of Sciences, on the Occasion of His 75^th Birthday  相似文献   

On the problem of determining the vertical gradients of gravity anomalies     

Petr Velkoborský  Reviewer M. Burša 《Studia Geophysica et Geodaetica》1974,18(3):232-237

Summary Green's theorem on harmonic functions makes it possible to determine the integral relationship between the harmonic function and its derivative with respect to the normal on a closed Lyapunov surface. The conditions of solvability are given by Fredholm's theory of integral equations. The solution for a sphere was presented by Molodenskii[3] and the general solution with the help of Molodenskii's parameter k by Ostach[4]. The present paper indicates a possibility of solving this problem with the help of a system of linear algebraic equations, a simplified modification of the Ostach-Molodenskii solution and, finally, a method, based on Eremeev's solution of the fundamental integral equation[5].  相似文献   

Active hydrate destabilization in Lake Baikal,Siberia?   总被引：1，自引：0，他引：1  

Marc De Batist  Jan Klerkx  Pieter Van Rensbergen  Maarten Vanneste  Jeffrey Poort  Alexander Y. Golmshtok  rei A. Kremlev  Oleg M. Khlystov  Petr Krinitsky 《地学学报》2002,14(6):436-442

ABSTRACT In this paper, we present new seismic and heat-flow data that show the base of the hydrate stability zone (BHSZ) in Lake Baikal to be locally characterized by abnormal variations in depth, with distinct regions of deeper-than-normal and regions of shallower-than-normal BHSZ. These variations are related to strong lateral variations in heat flow, and occur in close association with important rift-basin faults. Areas of shallow BHSZ are also characterized by the presence of several methane seeps and mud volcanoes at the lake floor. We infer that the seeps are the surface expression of escape pathways for overpressured fluids generated by the dissociation of pre-existing hydrates, in response to a thermal pulse caused by an upward flow of hydrothermal fluids towards the BHSZ. It thus seems that present-day hydrate dissociation in Lake Baikal is modulated by the tectonic activity in the rift rather than by – climatically controlled – changes in lake level or water temperature.  相似文献   

Regional development and the disintegration of Czechoslovakia     

Petr Pavlínek  Asssistant Professor 《Geoforum》1995,26(4):351-372

The breakup of Czechoslovakia on 31 December 1992 resulted in the emergence of a newly independent Slovakia and Czech Republic. The split is often interpreted as the result of ethnic nationalism. In contrast, this paper attempts to assess the influence of regional inequalities and uneven economic development on the split. Pre-World War Two Czechoslovakia was unable to address large regional differences between the Czech lands and Slovakia. The economic policies pursued by the state socialist governments following 1948 were directed toward the elimination of these differences through rapid industrialization of Slovakia. The economic transformation in Czechoslovakia after the collapse of state socialism resulted in reemergence of uneven development between Slovakia and the Czech lands, which contributed to the disintegration of the country. The links between economic issues and politics are discussed, and the paper shows how the regional inequalities and economic issues were used to justify the necessity of Slovak and Czech independence.  相似文献   

Book review     

Richard Barakat  Petr Vanicek  Randall L. Mackie  Jacek A. Majorowicz  Ley Truskinovsky  Andrea Borgia  Steven Carey  Ursula B. Marvin 《Pure and Applied Geophysics》1990,134(3):485-507

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Origin of the Zálesí U–Ni–Co–As–Ag/Bi deposit,Bohemian Massif,Czech Republic: fluid inclusion and stable isotope constraints     

Zdeněk Dolníček  Bohuslav Fojt  Walter Prochaska  Jan Kučera  Petr Sulovský 《Mineralium Deposita》2009,44(1):81-97

The Zálesí vein-type deposit is hosted by Early Paleozoic high-grade metamorphic rocks on the northern margin of the Bohemian Massif. The mineralization is composed of three main stages: uraninite, arsenide, and sulfide. The mineral assemblages formed at low temperatures (~80 to 130°C, locally even lower) and low pressures (<100 bars). The salinity of the aqueous hydrothermal fluids (0 to 27 wt.% salts) and their chemical composition vary significantly. Early fluids of the oldest uraninite stage contain a small admixture of a clathrate-forming gas, possibly CO₂. Salinity correlates with oxygen isotope signature of the fluid and suggests mixing of brines [δ ¹⁸O around +2‰ relative to standard mean ocean water (SMOW)] with meteoric waters (δ ¹⁸O around −4‰ SMOW). The fluid is characterized by highly variable halogen ratios (molar Br/Cl = 0.8 × 10⁻³ to 5.3 × 10⁻³; molar I/Cl = 5.7 × 10⁻⁶ to 891 × 10⁻⁶) indicating a dominantly external origin for the brines, i.e., from evaporated seawater, which mixed with iodine-enriched halite dissolution brine. The cationic composition of these fluids indicates extensive interaction of the initial brines with their country rocks, likely associated with leaching of sulfur, carbon, and metals. The brines possibly originated from Permian–Triassic evaporites in the neighboring Polish Basin, infiltrated into the basement during post-Variscan extension and were finally expelled along faults giving rise to the vein-type mineralization. Cenozoic reactivation by low-salinity, low-δ ¹⁸O (around −10‰ SMOW) fluids of mainly meteoric origin resulted in partial replacement of primary uraninite by coffinite-like mineral aggregates.  相似文献   

The Western Bohemia/Vogtland Region in the Light of the Webnet Network     

Horálek  Josef  Fischer  Tomáš  Boušková  Alena  Jedlička  Petr 《Studia Geophysica et Geodaetica》2000,44(2):107-125

The local network of digital seismic stations WEBNET monitors the seismic activitv of practically the whole region of Western Bohemia/Vogtland swarms. The network consists of ten short-period stations and one very broadband station. The paper describes the configuration of the network, instrumental equipment and the basic parameters of the stations. The method of and formula for computing the local magnitudes from the WEBNET and KRASLICE seismograms are also given. Based on continuous WEBNET observations in the period 1995-1999, we were able to improve the model of temporal and spatial energy release in the region, the principal characteristics of which are summarised in the paper. Apart from direct P and S waves, the WEBNET seismograms also contain other significant P- and S-type waves, provisionally interpreted as reflected PxP, SxS and SxP waves. The fundamental characteristics of these waves are given in the paper, and tentative mechanisms of their origination are discussed. The large residua in the travel times of the P and S waves, and the discrepancies in the seismograms recorded at stations located east of the principal focal zone are pointed out.  相似文献   

Dynamics of Stream Water Quality during Snowmelt and Rainfall – Runoff Events in a Small Agricultural Catchment     

Petr Fučík  Markéta Kaplická  Tomáš Kvítek  Jana Peterková 《洁净——土壤、空气、水》2012,40(2):154-163

Surface water quality can vary a lot with fluctuating discharge during a Rainfall – runoff event. This paper uses a set of hydrological and hydrochemical variables to explain concentration–discharge loops and hysteresis of ${\rm NO}_{3}^{- } $ , ${\rm NH}_{4}^{ + } $ and total suspended solids in a brook dewatering a small upland agricultural catchment in the Czech Republic. Our study is based on data collected by a continuous monitoring approach provided by an automatic ISCO sampler both from snow thawing and rainfall – runoff events. Methods of correlation, regression and principal component analysis (PCA) were employed to reveal possible relationships among the variables. For ${\rm NO}_{3}^{- } $ and ${\rm NH}_{4}^{ + } $ , we found several types of concentration–discharge loops due to the loop rotation direction and also the loop curvature shape, in mutual combinations, no matter which type of a hydrological event it was related to. PCA indicated that ${\rm NO}_{3}^{- } $ loops correlated mostly with the length of a rising hydrograph limb and with the slope of the initial phase of a falling hydrograph limb, 5‐day amount of precipitation and runoff coefficient. In case of ${\rm NH}_{4}^{ + } $ , the concentrations usually increased with elevated discharge, whereas PCA did not detect any closer linkages. For suspended solids, an unambiguous positive monotonic relationship was discovered. Although no definite pattern was found, this study showed the necessity of a continuous water quality monitoring system as an approach for capturing and understanding relationships between solute concentrations and runoff formation for tracing and modelling catchment pollution sources and describing transport processes.  相似文献   

A radar survey of M- and X-class asteroids     

Michael K. Shepard  Beth Ellen Clark  Ellen S. Howell  Jon D. Giorgini  Steven J. Ostro  Brian Warner  Petr Pravec  Thomas Bennett  Raoul Behrend  Josep Coloma  Andrew Rivkin 《Icarus》2008,195(1):184-205

We observed ten M- and X-class main-belt asteroids with the Arecibo Observatory's S-band (12.6 cm) radar. The X-class asteroids were targeted based on their albedos or other properties which suggested they might be M-class. This work brings the total number of main-belt M-class asteroids observed with radar to 14. We find that three of these asteroids have rotation rates significantly different from what was previously reported. Based on their high radar albedo, we find that only four of the fourteen—16 Psyche, 216 Kleopatra, 758 Mancunia, and 785 Zwetana—are almost certainly metallic. 129 Antigone has a moderately high radar albedo and we suggest it may be a CH/CB/Bencubbinite parent body. Three other asteroids, 97 Klotho, 224 Oceana, and 796 Sarita have radar albedos significantly higher than the average main belt asteroid and we cannot rule out a significant metal content for them. Five of our target asteroids, 16 Psyche, 129 Antigone, 135 Hertha, 758 Mancunia, and 785 Zwetana, show variations in their radar albedo with rotation. We can rule out shape and composition in most cases, leaving variations in thickness, porosity, or surface roughness of the regolith to be the most likely causes. With the exception of 129 Antigone, we find no hydrated M-class asteroids (W-class; Rivkin, A.S., Howell, E.S., Lebofsky, L.A., Clark, B.E., Britt, D.T., 2000. Icarus 145, 351-368) to have high radar albedos.  相似文献   

Estimation of finite seismic source parameters for selected events of the West Bohemia year 2008 seismic swarm     

Petr Kolář  Bohuslav Růžek 《Journal of Seismology》2015,19(2):403-421

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