Colour schlieren representation of compressional-stress fields with respect to focal zone study     

Jan Kozák  Reviewer V. Červený 《Studia Geophysica et Geodaetica》1973,17(4):314-320

Summary A method of colour schlieren recording of the compressional-stress field gradients, suitable for focal zone study on models, is suggested. The study presents colour schlieren records of the compressional-stress fields in loaded square plates, containing inhomogeneities which give instant quantitative information on these fields. If the inhomogeneity is shaped like Griffith's diagonal slit, good agreement is demonstrated between the experiment and the theoretical calculation of the compressional-stress field in a model.  相似文献   

Evolutionary stages of the Banská Stiavnica caldera and its post-volcanic structures     

V. Konečný 《Bulletin of Volcanology》1971,35(1):95-116

The remains of an extensive volcanic apparatus of the Tertiary « subsequent » volcanism have been identified in the ?tiavnické pohoric Mts. in the inner belt of the Carpathians. The volcanic apparatus, of stratovolcanic type, was formed during several stages of andesitic and rhyolitic volcanism with two caldera stages. During the final stage of volcanic activity the central collapsed area was uplifted as a horst, accompanied by the formation of grabens along the periphery of the central updomed area. The fractured zones of the horst periphery, as well as zones bordering separate subsided blocks of the central area became the sites of economic ore mineralization, with the formation of lead, zinc, copper, gold, and silver bearing veins. In the uplifted central block intrusions of diorite and granodiorite in the pre-volcanic basement have been exposed by erosion. Geological, petrographical, and petrochemical criteria, as well as absolute dating indicate direct chronological and genetic relationships between the diorite-granodiorite intrusions and extrusive volcanism.  相似文献   

Graphic intergrowths of feldspars and quartz in some Czechoslovak pegmatites     

P. Černý 《Contributions to Mineralogy and Petrology》1971,30(4):343-355

Graphic intergrowths of alkali feldspar+quartz, and plagioclase+quartz, occur together in pegmatites in the eastern part of the Czechoslovak Moldanubicum. They form zones between the finer-grained wall zone and the central blocky feldspar+quartz core. The normative Or-Pig-Q compositions of the graphic intergrowths and the Or-Ab-An contents of their feldspars show broad variations generally, but have a restricted range within individual pegmatites. At two localities studied in more detail, coexisting feldspars show gradual changes in composition, from the margins up to the innermost graphic pegmatite, compatible with fractional crystallization along the feldspar solidus-solvus intersection in the Or-Ab-An-Q-H₂O system, at different vapour pressures in different pegmatites. Two models are demonstrated for low and high pressure cases. The feldspar compositions from central blocky zones deviate from the magmatic fractional crystallizations paths; this corresponds with the general assumption that they crystallized from supercritical gaseous fluids.In these and in similar pegmatites, coexisting alkali feldspar+quartz and plagioclase + quartz intergrowths are interpreted as the last products of cotectic crystallization from an ultimately fractionated granitic magma. Positive correlation of Ab solid solution and quartz content in the potassic intergrowths suggests that these characteristics may be indicative of the relative pressure and temperature effective during their crystallization, when compared in pegmatites of the same bulk composition.  相似文献   

Determination of azimuths of simple horizontal pendula     

Lumír Skalský 《Studia Geophysica et Geodaetica》1969,13(4):400-416

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Ray amplitudes in a three-dimensional inhomogeneous medium   总被引：1，自引：0，他引：1  

Vlastislav Červený  Reviewer J. Vaněk 《Studia Geophysica et Geodaetica》1976,20(4):401-404

Summary A system of five ordinary differential equations of the first order to compute the geometrical spreading of the wave front of seismic body waves in a three-dimensional medium is suggested.  相似文献   

Influence of geological factors on seismic ground-motions (seismic microzoning of Prague)     

Jiří Zahradník  Vlastislav Červený  Vladimír Barták  Reviewer V. Kárník 《Studia Geophysica et Geodaetica》1981,25(4):343-355

Summary Seismic microzoning of Prague was performed using geological data and seismic response (ground shaking) computations. The Prague territory was covered by a square grid, each square 250 m×250 m being characterized by a simplified geological cross-section from the Earth's surface to the bedrock boundary. The data were obtained from detailed engineering-geological maps 1:5000. The geological cross-sections were transformed into a set of layered models, specified by the thicknesses of individual layers and corresponding compressional and shear-wave velocities, densities and parameters of the causal absorption. The seismic responses were computed by the matrix method. The main amplitude and frequency characteristics of the responses are demonstrated in the form of microzoning maps. The maps do not depend on the specific type of seismic excitation. They make it possible to predict the relative amplification of P and S waves, with respect to the bedrock outcrop, all over the city.  相似文献   

Correction of the level of magnification of the SVK vertical seismograph at the seismic station of průhonice (PRU)     

Vladimír Tobyáš  Reviewer J. Janský 《Studia Geophysica et Geodaetica》1981,25(1):99-103

Summary Drawing on the results of new measurements of the mechanical parameters of the SVK seismometer No. 5055, the level of magnification of the vertical seismograph used in the past, has been corrected. The amplitudes of the seismic waves from earthquakes in the period 1963–1978 have to be increased by 88% and the station correction for determining the magnitudes of earthquakes decreased by 0.274.  相似文献   

Amplitude curves ofP waves for the region of central Asia     

Jiří Vaněk  Aleksander Tskhakaya  Reviewer J. Janský 《Studia Geophysica et Geodaetica》1977,21(3-4):259-267

Summary The amplitude-distance curves of P waves, valid for the region of Central Asia, were derived in the distance range between 13° and 36° using observations of a network of eight Caucasian seismic stations. The curves are characterized by an anomalous increase of amplitudes between 13° and 20° followed by a large decrease of amplitudes in the distance range between 20° and 35°. Both the increase and decrease of amplitudes are interrupted by several local maxima. A comparison of the present amplitude curves with those derived for the regions of South-Eastern Europe and Asia Minor enabled us to correlate the individual local maxima of amplitude curves and to investigate the variation of their position due to the lateral inhomogeneity of the upper mantle structure in Eurasia.A. Tskhakaya deceased in 1970.  相似文献   

Computation of ray amplitudes of seismic body waves in vertically inhomogeneous media     

Vlastislav Červený  Věnceslava Pretlová  Reviewer I. Pšenčik 《Studia Geophysica et Geodaetica》1977,21(3-4):248-255

Summary Standard methods of interpolating the velocity-depth distribution v=v(z) do not guarantee the continuity of the first and second derivatives of velocity and generate false interfaces of a higher order. These false interfaces cause anomalies in the amplitude-distance curves. It is suggested to apply the smoothed spline approximation to the depth-velocity distribution z=z(v). In this case, the ray integrals can be evaluated in a closed form. The amplitude-distance curves become quite smooth and stable. All necessary formulae and numerical examples are presented.  相似文献   

Model of medium with cracks and its parameters obtained by observing longitudinal waves     

Jiří Jech  Reviewer V. Červený 《Studia Geophysica et Geodaetica》1983,27(4):366-371

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