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  • Articles  (74)
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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.
    Type of Medium: Electronic Resource
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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.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Physics of the Earth and Planetary Interiors 51 (1988), S. 25-35 
    ISSN: 0031-9201
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Physics of the Earth and Planetary Interiors 51 (1988), S. vii 
    ISSN: 0031-9201
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 6
    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.
    Type of Medium: Electronic Resource
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  • 7
    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.
    Type of Medium: Electronic Resource
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  • 8
    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.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Studia geophysica et geodaetica 21 (1977), S. 137-142 
    ISSN: 1573-1626
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Summary The space (time) delay of transmitted waves in the vicinity of the interface beyond the critical point is investigated on two-dimensional seismic models of a low velocity channel; results of laboratory experiments are compared with the conclusions of the theory. The effect of the time delay in field measurements is demonstrated by means of two typical geological formations.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Studia geophysica et geodaetica 22 (1978), S. 248-258 
    ISSN: 1573-1626
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Summary This paper is a continuation of[1]. It is mainly devoted to problems connected with the application of the method of determination of geometrical spreading in laterally inhomogeneous media with curved interfaces based on the solution of eight (in a three-dimensional medium) or two (in a two-dimensional medium) linear ordinary differential equations of the first order. The method of determination of the partial derivatives of velocity with respect to the special coordinates, connected with the ray under investigation, and the methods of determination of the initial values for the system of differential equations at the source and at the interfaces are proposed.
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