On the possibilities of horizontal propagation ofPc1 pulsations in the ionosphere     

Karel Prikner  Vladimír Vagner  Reviewer M. Hvoždara 《Studia Geophysica et Geodaetica》1985,29(3):269-279

Summary The vertical distribution of the contribution of the energy flux density due to the Alfvén(ordinary) wave, guided by the geomagnetic field(and propagating through the ionosphere to the Earth's surface) in the horizontal direction is demonstrated in the mechanism of the horizontal propagation of the Pc1 signal. The distribution with height is shown of the variations of the polarization characteristics of the propagating wave(e.g. the rotation of the polarization plane, changes in ellipticity, attenuation, etc.), which are the result of coupling in the denser layers of the low ionosphere in which also suitable isotropic(extraordinary) modes are generated. The results obtained using the method described in[4, 13] are demonstrated on a model of the daytime ionosphere under incidence of ordinaryL-modes, frequency f=0.3 Hz, and various meridional angles at the ionosphere.

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auauma anmau uaa Pc1 naa m an¶rt;u ¶rt;u nmmu ma uu uma anauu maum n n¶rt; , anma u nmu. naa m an¶rt;u uu aamumu nuauu anma (nauau nmu nuauu, uu unmumu, amau u m.¶rt;.), m m ¶rt;mu au¶rt;mu na uu u . ¶rt; mum n¶rt;¶rt;u umn() ¶rt;. mam num m¶rt; [4, 13] ¶rt;mua ¶rt;u ¶rt; u nu na¶rt;uu a u L-¶rt; amm f=0,3 n¶rt; au u¶rt;uau au.

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Geochemical Investigations of Stratabound Gunga Barite Deposits of Khuzdar (Balochistan), Pakistan     

Viqar HUSAIN  Hameedullah KHAN  Klaus GERMANN  Karel ZAK 《Resource Geology》2002,52(1):49-58

Abstract: The Gunga barite deposits occur in carbonate clastic marine sequence of Jurassic age. These rocks are widely spread in Khuzdar-Lasbela belt which host important stratabound barite and zinc-lead deposits of Pakistan. These rocks are intricately folded and extensively faulted. The Gunga are low temperature hydrothermal deposits occurring as a series of disconnected lenses a few meters thick. Two mineralized horizons are recognized: barite in the upper zone, sphalerite and galena in the lower zone. Four types of barite mineralization occurs in Gunga stratabound replacement associated with 1) fracture filling, 2) open space fillings in solution collapsed breccia, 3) replacement in fault, and 4) veinlets associated with all these three types. The wall rocks of the Gunga deposits have also been altered by silicification, leaching and ferruginization.
The sulfur isotope values of most of the Gunga barite samples range from 23.8 to 27.8 per mil with an average of 26.4 per mil, which is very close to the average of isotopic values of epigenetic carbonate hosted Late Paleozoic Missouri barite deposits. The Gunga like other barite and sulfide deposits of Khuzdar-Lasbela belt are Mississippi Valley type, stratabound and of replacement origin precipitated from connate brines expelled during the incipient rifting of India from Gondwana land in the Late Jurassic and Early Cretaceous periods. The low content of copper, lead and zinc in the Gunga barite deposits suggests that these deposits were not formed in proximity to an igneous source of the ore solution.
The Gunga deposits are epigenetic and stratabound as their mineralization is structure controlled. There is an evidence of transgressive nature of host rock and wall rock alteration which are absent in stratiform or bedded deposits.  相似文献   

Triple oxygen isotope composition of Australasian tektites     

Karel k  Roman Skla  Andreas Pack  Luk&#x; Ackerman  &#x;rka K&#x;íov 《Meteoritics & planetary science》2019,54(5):1167-1181

Major and trace element analyses and triple oxygen isotope measurements were performed on 11 individual specimens of Australasian tektites (AAT) with exactly known field positions from Laos. The sample set was dominated by Muong Nong‐type tektites (MNAAT), including separated layers of glass of different appearance and chemistry from four samples. This first larger set of oxygen isotope data of MNAAT revealed the δ¹⁸O range 8.7 ≤ δ¹⁸O ≤ 11.6‰ on VSMOW2 scale (12 analyses), only slightly wider than the previously reported range for splash‐form AAT. The Δ’¹⁷O values of MNAAT (?0.098 ≤ Δ’¹⁷O ≤ ?0.069‰; 12 analyses) and splash‐form AAT (?0.080 ≤ Δ’¹⁷O ≤ ?0.068‰; three analyses) are all in the range of data typical for terrestrial crustal rocks, with no mass‐independent oxygen isotope fractionation (from impactor or from exchange with atmospheric O₂) being observed.  相似文献   

The Phobos gravitational field modeled on the basis of its topography     

Zdeněk Martinec  Karel Pěč  Milan Burša 《Earth, Moon, and Planets》1989,45(3):219-235

The parameters of the best-fitting ellipsoid have been derived using the latest spherical harmonics of the Phobos topography (Duxbury, 1989) by solution of non-linear overdetermined inverse problem. The lengths of the equatorial axes of the ellipsoid have been determined (a = 12.9 km, b = 11.4 km). They are nearly the same as established by Duxbury (ibid.) on the basis of the linearized relationship between the squared lengths of ellipsoidal axes and the topography coefficients C ₂₀ and C _22. The length of the polar axis (c = 9.1 km) differs of about 20% from Duxbury's value. Supposing mass homogeneity of Phobos, the Stokes parameters of the external gravitational field have been derived up to those of the sixth degree and order. The large irregularities in the Phobos figure cause the values of the Duxbury's potential coefficients be fairly inaccurate except the harmonics C ₂₀, C ₃₂, S ₄₃ and S ₅₁, i.e. linearized relationship between gravity and topography cannot be applied for Phobos. Finally, positions of the centre of figure and the directions of the principal axes of inertia have been established.  相似文献   

Lever constants and gravity meter sensitivity     

Vladimír Tobyáš  Karel Diviš  Reviewer Z. Šimon 《Studia Geophysica et Geodaetica》1982,26(3):231-237

Summary For the Worden, Sharpe and Scintrex gravity meters, the lever constants were derived from the amplitude response to the vertical motion and their relation to the sensitivity of the gravity meter was verified. It is then possible to calculate the lever constants for the actual sensitivity of the gravity meter without further measurements and to apply them to estimating the dynamic behaviour of the reading beam.  相似文献   

Attenuation ofSH waves before cut-off frequency     

Karel Pêê 《Studia Geophysica et Geodaetica》1964,8(2):140-147

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Theorie der im elastischen halbraum durch eine flächenförmige quelle erregten wellen. (1. teil)     

Pěč  Karel 《Studia Geophysica et Geodaetica》1959,3(2):135-153

Studia Geophysica et Geodaetica - В работе рассматривается...  相似文献   

Geophysical Field Pattern in The West Bohemian Geodynamic Active Area     

Švancara  Jan  Gnojek  Ivan  Hubatka  František  Dědáček  Karel 《Studia Geophysica et Geodaetica》2000,44(2):307-326

Regional geophysical data from detailed gravity survey, airborne magnetometry and gamma-ray spectrometry were analysed in order to determine the subsurface extent of contrasting geological bodies and to highlight subtle anomalies which can be related to the occurrence of earthquake swarms. Potential field data were compiled into contour and colour-shaded relief maps suitable for detecting structural tectonic elements. A shaded relief map of the horizontal gradient of gravity was used to detect considerable structural and tectonic features. The results of airborne gamma-ray spectrometry, showing the regional total gamma-ray activity, abundance of uranium, thorium and potassium, were included in this study. Only the two most instructive maps – the total gamma-ray activity and the abundance of potassium are shown. The main line of epicentres Nový Kostel – Poátky coincides well with the N-S configuration of abundances of these natural radioactive elements. The epicentres of micro-earthquakes detected by the local seismological network KRASLICE for the 1991 to 1998 period were plotted in the geophysical maps. The hypocentres of earthquakes in the main epicentral zone at Nový Kostel were projected onto the crustal density model based on the interpretation of seismic reflection profile 9HR and gravity data. The average distance between the Nový Kostel epicentral zone and the seismic profile was 4-5 km. Based on the interpretation of gravity data the hypocentres of the main epicentral zone seem to be associated with the western margin of the Eibenstock - Nejdek (Karlovy Vary) Pluton and, beside that, they follow the depth level where the allochthonnous part of the Saxothuringian Zone is thrust over the European parautochton. A drawing of the geodynamic model of the area is also shown.  相似文献   

Types of soft-sediment deformation structures in a lacustrine Ploužnice member (Stephanian,Gzhelian, Pennsylvanian,Bohemian Massif), their timing,and possible trigger mechanism     

Marcela Stárková  Karel Martínek  Radek Mikuláš  Nicholas Rosenau 《International Journal of Earth Sciences》2015,104(5):1277-1298

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Evaluation of meteorological controls of reconstructed rockfall activity in the Czech Flysch Carpathians     

Karel Šilhán  Rudolf Brázdil  Tomáš Pánek  Petr Dobrovolný  Lucie Kašičková  Radim Tolasz  Ondřej Turský  Marek Václavek 《地球表面变化过程与地形》2011,36(14):1898-1909

Rockfall is an important process in the final sculpturing of escarpments and scree slopes that originate in bedrock landslides in the Flysch Carpathians. The spatio‐temporal characteristics of rockfall activity were studied at four localities representative of old landslides in the highest part of the Czech Flysch Carpathians (Moravskoslezské Beskydy Mountains). Historical activity, chronology, and spatial context of rockfall activity were reconstructed using dendrogeomorphic techniques and rockfall rate index (RR). A total of 1132 increment cores from 283 trees growing in the rockfall transport and accumulation zones enabled the dating of 989 rockfall events. Reconstruction of a 78‐year‐long RR chronology suggests similar rockfall histories and trends at all study sites, indicating the existence of major common factors driving rockfall dynamics in the region. Temporal analysis and correlation of the RR series obtained with monthly mean temperatures, numbers of days with temperature transitions through 0 °C and monthly precipitation totals show that meteorological characteristics have evident but variable influence on rockfall activity. The most important factor is the effect of freeze–thaw cycles throughout the year, supplemented by low temperatures, especially during autumn. The influence of precipitation totals is of lesser importance. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献