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  • Articles  (31)
  • 1985-1989  (16)
  • 1970-1974  (15)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 92 (1971), S. 115-132 
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary An irregular wave group (here called pseudospherical), the existence of which is connected with the velocity boundary at which the velocity decreases discontinuously, is investigated. A schlieren modelling device was chosen for a model investigation of this wave since it permits the investigation of wave fields inside the measured models. The model consisted of two layers of transparent gels, the source lay in the layer of higher velocity. The measurements have shown that an irregular wave in the layer of lower velocity exists only in a certain region along the boundary; its wave front has a spherical form and its intensity decreases rapidly with increasing distance of the source from the boundary. The wave always comes only after the regular refracted wave which conforms with the ray theory. These properties correspond to the properties of a wave first described byOtt [1]3) andBrekhovskikh [2]. In the conclusion of the present paper the possibilities of recording pseudospherical waves in seismology are outlined.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 99 (1989), S. 0 
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: An approximate hybrid approach to computing high-frequency body wave synthetic seismograms in 2-D and 3-D laterally varying layered structures containing thin transition layers is suggested. It combines the ray method with the matrix (reflectivity) method. The ray method is applied to thick layers with smooth variations of velocity and the reflectivity method is applied to thin transition layers. Alternatively, the method of summation of Gaussian beams is used instead of the ray method in the hybrid code. An algorithm and the relevant program package BEAM87, designed for such hybrid computations in 2-D laterally varying layered structures containing one laterally varying thin transition layer, are briefly described. The thin transition layer may represent a region of a high velocity gradient, a laminated region, a region of a low Q, etc. It is simulated by a stack of very thin layers. The accuracy of the hybrid computations is tested on 1-D models by the comparison with reflectivity-method computations. The hybrid method yields sufficiently accurate results for transition layers, the thickness of which is smaller than one half of the prevailing wavelength of the wavefield under consideration, particularly for small angles of incidence. For reflected waves, the best accuracy is obtained for subcritical reflections, but the accuracy is lower for critical and overcritical reflections. The accuracy in the critical region is improved, if the Gaussian beam summation method is used instead of the ray method in the hybrid scheme. Numerical examples of synthetic body wave seismograms for a laterally varying model containing thin transition layers of various types are presented.
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 99 (1989), S. 0 
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: A concept of a factorized anisotropic inhomogeneous (FAI) medium is introduced. In the FAI medium, the position dependent density normalized elastic parameters aijkl(Xi) can be factorized in the following sense: aijkl(Xi) =f2(xi)Aijkl, where Aijkl are constants, independent of Cartesian coordinates xi, and f(xi) is an arbitrary continuous function of xi. Thus, all the density normalized elastic parameters aijkl(xi) in the FAI medium depend on the coordinates xi in the same way, but the generality of anisotropy and of inhomogeneity is not restricted. The factorization of aijkl(xi) leads to a factorization of certain important ray theory expressions and equations (eikonal equation, etc.), and to particularly simple ray tracing and dynamic ray tracing. For certain types of FAI media, these equations may even be solved analytically or semianalytically.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Studia geophysica et geodaetica 15 (1971), S. 421-423 
    ISSN: 1573-1626
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Zusammenfassung Bei Verfolgung der Entstehung und Formierung der durch eine explosive Kugelquelle erregten Druckwellen steht die Frage ihres Frequenzgehalts im Vordergrund. Der Frequenzgehalt dieser Wellen wurde durch die Abhängigkeit ausgedrückt (2), die die Änderungen der relativen Breite des Amplitudenspektrums (1) vom Gewicht und von der Entfernung der Quelle angibt. Aus(2) erfolgt, dass der Frequenzgehalt der Druckwellen mit wachsender Entfernung und Grösse der Ladung exponential sinkt, wobei die Steilheit dieses Abfalls für höhere Grössen der Ladung kleiner ist. Das Herabsetzen des Frequenzgehalts dieser Wellen verursacht, dass die maximate spektral Dichte in grösseren Entfernungen von der Quelle markanter wird.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Studia geophysica et geodaetica 17 (1973), S. 115-122 
    ISSN: 1573-1626
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Резюме Иссле¶rt;уеmся оnре¶rt;еленuе уnру uх nосmоянных nо скоросmям объемных волн. Меmо¶rt;ом nосле¶rt;овamельных nрuблuженuŭ решaеmся сuсmемa урaвненuŭ muna (6) u (10). Для мamерuaлов с высокоŭ aнuзоmроnuеŭ вмесmо скоросmеŭ nоnеречных волн можно uсnользовamь uх оценкu, коmорые nовmоренuем рaсчеma уmочняюmся (фu . 2). Для вычuсленuя уnру uх nосmоянных необхо¶rt;uмо знamь скоросmu nро¶rt;ольных волн мuнuмaльно в 15mu нanрaвленuях u скоросmu обеuх nоnеречных волн мuнuмaльно в шесmu нanрaвленuях. Прu uсnользовaнuu оценок скоросmеŭ nоnеречных волн необхо¶rt;uмо знamь скоросmu nро¶rt;ольных волн мuнuмaльно ¶rt;ля 21 о нanрaвленuя.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Studia geophysica et geodaetica 17 (1973), S. 255-260 
    ISSN: 1573-1626
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Резюме Меmо¶rt; вычuсленuя уnру uх nосmоянных uз скоросmеŭ nро¶rt;олЩных волн, оnuсaнныŭ в[4], был uсnолЩовaн ¶rt;ля обрaзцa uзвесmнякa с небольщuм коэффцuенmом aнuзоmроnuu. Для maко о мamерuaлa возможно нaŭmu ря¶rt; совокуnносmеŭ уnру uх nосmоянных, коmорые хорощо annроксuмuруюm кuнемamuческuе u ¶rt;uнaмuческuе своŭсmвa nро¶rt;олъных волн. Девяmъ uз эmuх nосmоянных uмеюm о¶rt;нознaчные, nрaвuльные знaченuя. Для осmaльных ¶rt;венa¶rt;цamu nосmоянных мозно uз скоросmеŭ nро¶rt;ольных волн оnре¶rt;елumь mолько щесmъ условных урaвненuŭ.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Studia geophysica et geodaetica 16 (1972), S. 126-152 
    ISSN: 1573-1626
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Zusammenfassung Es werden die Grundbeziehungen für die Berechnung von Strahlen seismischer Wellen in inhomogenen Milieus abgeleitet, in denen die Geschwindigkeit allgemein von drei krummlinigen Koordinaten abhängt. Die angeführten Beziehungen stellen ein System von gewöhnlichen Differentialgleichungen erster Ordnung dar. Die numerische Lösung dieses Systems bietet eine Möglichkeit, die Strahlendiagramme, Laufzeitkurven und Isochronen für die gegebenen Geschwindigkeitsmodelle zu konstruieren. Aufmerksamkeit wird ebenfalls dem Einfall der Strahlen auf eine unebene Grenzschicht gewidmet. Die Beziehungen für die Berechnung reflektierter und refraktierter Strahlen werden abgeleitet. Anhand der abgeleiteten Beziehungen werden Strahlendiagramme und Laufzeitkurven für eine Geschwindigkeitsverteilung berechnet, die durch die vorläufige Interpretation der Ergebnisse von seismischen Tiefensondierungen am tschechoslowakischen Teil des Profils VI gewonnen wurden.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Studia geophysica et geodaetica 32 (1988), S. 287-299 
    ISSN: 1573-1626
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Description / Table of Contents: Summary The dependence between Pn-wave velocities and the surface heat flow, temperature at the core-mantl boundary and thickness of the Earth's crust for continents (Europe, Asia, North America and Australia) was investigated statistically in connection with the problem of lateral inhomogeneities in the upper mantle. The relations obtained were compared with those determined under laboratory conditions. The conclusion is that temperature and pressure effects may provide additional explanations of the regional variations of Pn-wave velocities observed in most continents.
    Notes: Резюме Зaвuсuмосmь меж¶rt;угрaнuчнымu скоросmямu nро¶rt;ольных волн нa nоверхносmu Мохоровuчuчa(Pn ), nоверхносmным mеnловым nоmоком, mемnерamуроŭ нa Мохо u мощносmью земноŭ коры конmuненmов былa uссле¶rt;овaнa в связu с воnросом о нрuчuнегорuзонmaльных нео¶rt;норо¶rt;носmеŭ скоросmu Pn. Оnублuковaнные ¶rt;aнные о резульmamaх лaборamорных uссле¶rt;овaнuŭ уnругuх своŭсmв nоро¶rt; верхнеŭ мaнmuu в условuях высокuх ¶rt;aвленuŭ u mемnерamур нaхо¶rt;umся в сооmвеmсmвuu с резульmamaмu nре¶rt;лaгaемоŭ рaбоmы. Делaеmся выво¶rt;, чmо регuонaльные uзмененuя скоросmеŭ Pn-волн ¶rt;ля больщеŭ чaсmu конmuненmaльноŭ коры оnре¶rt;еляюmся рaзлuчuем mермо¶rt;uнaмuческuх условuŭ нa nоверхносmu Мохоmовuчuчa.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Studia geophysica et geodaetica 15 (1971), S. 147-160 
    ISSN: 1573-1626
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Summary Following the recommendation of the European Seismological Commission (Copenhagen 1966) to carry out comparative measurements on simple seismic models with a prescribed velocity-depth distribution (test models), an attempt was made to compare results obtained with different model techniques. In the present paper, model investigations with the first two proposed test models carried out by 2- and 3-dimensional model techniques are described. Seismogrammes, travel-time curves and amplitude-distance curves of the models investigated are given. A quantitative comparison of the results shows a satisfactory agreement.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Studia geophysica et geodaetica 17 (1973), S. 314-320 
    ISSN: 1573-1626
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: 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.
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