An analytical migration method for crustal wide angle reflections     

K. L. Kaila  K. Roy Chowdhury  V. G. Krishna  Reviewer V. Červený 《Studia Geophysica et Geodaetica》1982,26(3):254-271

Summary An analytical migration method is developed for inverting wide angle seismic reflection travel time data with proper migration. In this method the concept of effective velocity (V _eff ) in the vertically inhomogeneous earth has been used, which takes into account the refraction effect. It is shown that the migration process in this case becomes extremely rapid as curved ray paths are replaced by equivalent straight paths. A post migration sliding correction is found to be necessary, which arises due to the non-collinearity of the recording point, reflection point and the image point in the equivalent straight path geometry for dipping reflectors. Calculations for some representative dips show that, for the depths and recording ranges of interest in DSS, the vertical component of the sliding correction is negligible compared to the horizontal component. However, even the horizontal component is not significant for reflectors with gentle dips. The effect of certain simplifying assumptions in the estimation of V _eff is shown to be within the error limits of velocity determination. A computer programme package has been written for carrying out the migration. The method yields more accurate results in various theoretical and field cases than the conventional graphical wave front methods which are at present widely used for crustal reflection work.  相似文献   

Perturbations in satellite orbits due to variations in the Earth's rotation     

Milan Burša  Reviewer J. Kostelecký 《Studia Geophysica et Geodaetica》1983,27(4):324-331

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Laboratory investigations on fault plane induced tensile cracks     

Jan Kozák  Jan Šílený  Ludvík Waniek  Reviewer V. Červený 《Studia Geophysica et Geodaetica》1981,25(4):332-342

Summary Tensile cracks induced by stress concentration around a fault plane in physical models under uniaxial load were analyzed. The results characterizing the decisive role of the fault plane inclination to the the stress direction are presented. Two stages of tensile crack life were determined, i.e. the first, seismoactive stage, accompanied by seismic energy release and the second aseismic one characterized by low velocity of crack propagation. Results obtained seem to be relevant to a better understanding of the character and regime of actual seismoactive faults.  相似文献   

Anomalous behaviour of seismic waves at an interface between anisotropic media     

Jan Šílený  Reviewer V. Červený 《Studia Geophysica et Geodaetica》1981,25(2):152-159

Summary An account of possible anomalous effects in reflection and refraction of elastic waves at an interface between anisotropic media is presented. These effects are due to anisotropy and they cannot occur at an interface between isotropic media. The shape of the slowness surface (its local deviations from spherical symmetry) is the decisive factor for appearance of these effects. A numerical example of such anomalous behaviour of elastic waves at a free boundary of the crystal of spinel is presented.  相似文献   

On the disappearance of the imf sector structure effect in the lower atmosphere in 1974–1977     

Jan Laštovička  Reviewer L. Křivský 《Studia Geophysica et Geodaetica》1981,25(2):208-210

1974–1977. aum n mun ma nu mau nam aum n, a¶rt;a anu aum amumu, m, m a¶rt;am u u am, nmu uam. ¶rt;am uuu nuu m uu.  相似文献   

Reliability of focal mechanism determination     

Karel Klíma  Libuše Ruprechtová  Reviewer V. Červený 《Studia Geophysica et Geodaetica》1981,25(3):224-230

Summary The fault plane solution determined by means of a computer algorithm, correlating the radiation pattern with the distribution of observations, was investigated from the point of view of its reliability. The maximum of the correlation function R corresponds to the optimum solution found by the computer. If the families of nodal lines fitting the decreased correlation function R —dR retain the character of the optimum solution even whendR increases, we assume that the solution has been determined with a sufficient accuracy.  相似文献   

Verification of the Litho-spheric Structure along Profile Uppsala-Prague Using Surface Wave Dispersion     

Novotný  O.  Grad  M.  Lund  C.-E.  Urban  L. 《Studia Geophysica et Geodaetica》1997,41(1):15-28

Experimental dispersion curves of Rayleigh and Love waves along the Uppsala-Prague profile have been determined using records of several Italian earthquakes. To interpret the dispersion data, results of previous geophysical investigations in this region were first analyzed. Seven blocks of the crust and upper mantle were distinguished along the profile on the basis of deep seismic sounding and other seismic data. Layered models were proposed for these blocks. Computation of Rayleigh and Love waves shows a large differentiation of theoretical dispersion curves for the northern (Precambrian) and southern (Palaeozoic) part of the profile. A laterally inhomogeneous model for theUppsala - Prague profile, composed of the seven blocks, satisfies the surface wave data for the profile. Moreover, a mean layered model for the whole profile has also been proposed.  相似文献   

Croatia and Central Europe — the geopolitical relationship     

Duško Topalović  Miroslav Krleža 《GeoJournal》1996,38(4):399-405

The position of Croatia on the border of larger geographic wholes (Central Europe, the Mediterranean, the Balkans) makes it a transitional region for these larger areas. However, the Pannonian region of Croatia, as the largest part of its national territory, places it in the ranks of the Central European states. The long historical ties of the Croatian lands with the Austrian and Hungarian centers of Central European power also confirm Croatia's affiliation with Central Europe. The cultural, civilization, religious and other characteristics, which today ease Croatia's communications with Central European countries, are unavoidable. With state independence, Croatia acquired the political sovereignty vital for its Central European orientation and was liberated from the problems of the Balkans, although it is still struggling for its territorial integrity. Croatian statehood was realized soon after the reunification of Germany, which in fact renewed the concept and content of Central Europe. This fact opened many questions tied to the rivalry and political balance of the European powers, which is also connected to the geopolitical position of Croatia.  相似文献   

Protosolar nebula and composition of comets     

Vladimir Vanýsek  Zdeněk Moravec 《Earth, Moon, and Planets》1995,68(1-3):95-106

Comets seem to be composed of matter, which is supposed to have the same molecular composition as protosolar nebula. Although there are no unbiased evidence that cometary nuclei retain the molecular composition inherited from the protosolar cloud, the observed properties of comets indicate that there is at least a resemblance between cometary composition and the material properties of dense interstellar clouds. Therefore the origin of comets could be searched in the cold stages of the protosolar nebula and molecular abundances of grain mantles in this nebula may be similar to those in the cometary dust. It is suggested that comets may contain pristine, virtually unaltered protosolar material and their study might be very relevant way to more information about processes in early stages of the solar nebula. Our knowledge about composition of the cometary nucleus is still relatively scarce, but we can partly deduce it from data obtained either by ground-based spectroscopy or by in situ mass spectrometry from space experiments. Most important were the discovery of fluffy CHON particles composed partly or even completely from compounds containing light elements. No consensus concerning the presence of interstellar pristine matter in comet has been reached from various approaches to determine the relationship between comets and interstellar grains. Most of these studies are based on infrared spectroscopy. Another method is the comparison on the chemical models of the protosolar nebula with the volatile compounds of the cometary nuclei. Both gas-phase and grain-surface chemistry are considered and initial gas-phase atomic abundances are assumed to be protosolar. The cometary matter is certainly not identical with the typical material of dense interstellar cool dense clouds, but it is closer to it than any other type of matter in solar system so far accessible to us. The data from comets combined with models of chemical evolution of matter in environment similar as prevailed the early stage of presolar nebula may at least impose constrains on the condition for comet formation. Here presented study is a preliminary contribution to such studies.  相似文献   

On the position of the maximum of the amplitude curves of reflected waves     

Vlastislav Červený 《Studia Geophysica et Geodaetica》1962,6(3):215-234

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