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  • 1
    Unknown
    Basel, Boston, Berlin : Birkhäuser
    Keywords: seismic waves ; geophysics ; seismology
    Description / Table of Contents: The special issue contains contributions presented at the international workshop Seismic waves in laterally inhomo- geneous media IV, which was held at the Castle of Trest, Czech Republic, May 22-27, 1995. The workshop, which was attended by about 100 seismologists from more than 10 countries, was devoted mainly to the current state of theoretical and computational means of study of seismic wave propagation in complex structures. The special issue can be of interest for theoretical, global and explorational seismologists. The first part contains papers dealing with the study and the use of various methods of solving forward and inverse problems in complicated structures. Among other methods, discrete-wave number method, the finite-difference method, the edge-wave supperposition method and the ray method are studied and used. Most papers contained in the second part are related to the ray method. The most important topics are two-point ray tracing, grid calculations of travel times and amplitudes and seismic wave propagation in anisotropic media.
    Pages: Online-Ressource (342 Seiten) , Illustrationen, Diagramme, Karten
    ISBN: 9783764356484
    Language: English
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  • 2
    Unknown
    Basel, Boston, Berlin : Birkhäuser
    Keywords: seismic waves ; geophysics ; seismology
    Description / Table of Contents: The special issue contains contributions presented at the international workshop Seismic waves in laterally inhomogeneous media IV, which was held at the Castle of Trest, Czech Republic, May 22-27, 1995. The workshop, which was attended by about 100 seismologists from more than 10 countries, was devoted mainly to the current state of theoretical and computational means of study of seismic wave propagation in complex structures. The special issue can be of interest for theoretical, global and explorational seismologists. The first part contains papers dealing with the study and the use of various methods of solving forward and inverse problems in complicated structures. Among other methods, discrete-wave number method, the finite-difference method, the edge-wave supperposition method and the ray method are studied and used. Most papers contained in the second part are related to the ray method. The most important topics are two-point ray tracing, grid calculations of travel times and amplitudes and seismic wave propagation in anisotropic media.
    Pages: Online-Ressource (372 Seiten)
    ISBN: 9783034890496
    Language: English
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 148 (1996), S. 343-343 
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 148 (1996), S. 1-1 
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 148 (1996), S. 39-76 
    ISSN: 1420-9136
    Keywords: Seismic waves ; finite differences of the 2nd and 4th order ; 2-D and 3-D seismic modeling ; accuracy ; elasticity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The accuracy of finite-difference schemes of the 2nd and 4th order in 2-D and 3-D regular rectangular grids is studied. The method of designing the schemes and estimating their accuracy is proposed. The paper is devoted to the point schemes, expressed in terms of the discretized (point) values of the wave field and material parameters. Only the common schemes applicable in smooth parts of seismic models, outside structural interfaces, are taken into account. Finite differences at structural interfaces are studied elsewhere. The inaccuracy of finite-difference schemes is governed, above all, by the error in the phase velocity, caused by discretization. This error is estimated for several finite-difference schemes. It is explicitly dependent on the direction of propagation and on wave polarization. The maximum phase-velocity error over all directions of propagation enables the accuracy of the individual schemes to be appreciated in order to select the best one. The proposed approach is general and applicable to other finite-difference schemes, for example, of the 6th and higher orders.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 148 (1996), S. 337-342 
    ISSN: 1420-9136
    Keywords: Hypocentre determination ; seismic model ; accuracy ; arrival-time residuals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract It is shown that the arrival-time residuals and hypocentre mislocation are two mutually independent consequences of the inaccurate seismic model and inaccurately measured arrival times. The minimum residuals resulting from the kinematic hypocentre determination contain no information on the accuracy in determining the hypocentre position.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 148 (1996), S. 539-563 
    ISSN: 1420-9136
    Keywords: Seismic waves ; first-arrival travel times ; slowness vectors ; ray tracing ; accuracy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A new computational scheme for calculating the first-arrival travel times on a rectangular grid of points is proposed. The new proposed method is of second-order accuracy. This means that the error of the calculated travel time is proportional to the second power of the grid spacing. The method should be sufficiently accurate for all applications in smooth seismic models. On the other hand, the method is not, in its present form, proposed for models with structural interfaces which make the method unstable and generate travel-time errors of the first order. Equations are also presented for the appropriate evaluation of the errors of calculated travel times to check their accuracy, and the proposed method is compared with other numerical methods. The method is developed, described and demonstrated in 2-D, but may also be extended to 3-D models and to general models with structural interfaces.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 116 (1994), S. 0 
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: An efficient algorithm of the network shortest path calculation of rays and traveltimes of the first arrivals is described. The traveltime error of such computations is estimated. The rough estimate of the relative traveltime error is evaluated locally at all network nodes prior to network ray tracing, and is minimized by means of a proper choice of the sizes of forward stars. In this way, the structure of the network is adjusted for a particular model and for a particular computer memory. After network ray tracing, the error estimate is refined and the absolute error bounds of the calculated traveltimes are evaluated. The method and its accuracy are demonstrated on numerical examples.
    Type of Medium: Electronic Resource
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  • 9
    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 method of computing synthetic seismograms by means of the three-parametric summation of Gaussian packets over space is proposed. The expansion of the wavefield specified in terms of a complex-valued amplitude and a phase function into Gaussian packets is very similar to the expansion into Gaussian beams, with the additional summation over points along the rays. Initial conditions for the wavefield, for which the initial directions of the rays are time independent (e.g. the point source), are assumed. The summation is performed in the frequency domain. The synthetic seismograms are then evaluated by the Fast Fourier transform for any source time function. The method should not require a substantial increase of the computational time with respect to the ray and Gaussian beam methods.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Studia geophysica et geodaetica 28 (1984), S. 237-247 
    ISSN: 1573-1626
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Description / Table of Contents: Summary The application of Maslov asymptotic theory in a general 3-D mixed subspace of 6-D complex phase space is proposed to obtain the integral superpositions of Gaussian packets and beams. The ray method and the superposition of plane waves (Maslov method of Chapman and Drummond [7]) are special limiting cases of the above mentioned approach. The same high-frequency asymptotic expansion formulae for seismic body waves were derived previously in [8] using the Gaussian beam method.
    Notes: Резюме Прuложенuе aсuмnmоmuческоŭ mеорuu Мaсловa к общему mрехмерному смещaнному nо¶rt;nросmрaнсmву щесmuмерного фaзового nросmрaнсmвa nре¶rt;ложено ¶rt;ля nолученuя uнmегрaльных суnерnозuцuŭ Гaуссовых naкеmов u nучков. Суnерnозuцuя nлоскuх волн u лучевоŭ меmо¶rt; являюmся сnецuaльнымu nре¶rt;ельнымu случaямu nре¶rt;ложенного nо¶rt;хо¶rt;a. Те же сaмые высокочaсmоmные aсuмnmоmuческuе формулы былu рaньще nолучены меmо¶rt;ом Гaуссовых nучков [8].
    Type of Medium: Electronic Resource
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