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  • 1
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    Three-dimensional sensitivity kernels for finite-frequency traveltimes: the banana-doughnut paradox (1999)
    In:  Geophys. J. Int., Zagreb, 3-4, vol. 137, no. 3, pp. 805-815, pp. 1431, (ISSN: 1340-4202)
    Details
    Publication Date: 1999
    Keywords: Three dimensional ; Wave propagation ; Waves ; Inhomogeneity ; Seismology ; Travel time ; Shear waves ; Tomography ; Frechet ; derivatives ; GJI
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    BIBLIOGRAPHY SEISMOLOGY
  • 2
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    Theoretical Global Seismology (1998)
    Princeton Univ. Press
    In:  Princeton, N.J., XIV+1025 pp., Princeton Univ. Press, vol. 231, no. 3, pp. 2-203, (ISBN 0-470-02298-1)
    Details
    Publication Date: 1998
    Keywords: Seismology ; Elasticity ; NOModelling ; Surface waves ; Waves ; Textbook of geophysics ; Handbook of geophysics ; Wave propagation
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    BIBLIOGRAPHY SEISMOLOGY
  • 3
    Electronic Resource
    Electronic Resource
    Geophysics Latest spin on the core (1999)
    [s.l.] : Macmillan Magazines Ltd.
    Nature 402 (1999), S. 26-27 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Is the Earth's inner core rotating slightly faster than the mantle and crust? This is a question that has perplexed geophysicists since it was first raised five years ago. The latest study comes from Laske and Masters (page 66 of this issue), who have taken a new approach to the problem and ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/46918
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Validity of surface-wave ray theory on a laterally heterogeneous earth (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 123 (1995), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: A necessary and sufficient condition for the validity of surface-wave ray theory is 〈inlineGraphic alt="inline image" href="urn:x-wiley:0956540X:GJI757:GJI_757_mu1" location="equation/GJI_757_mu1.gif"/〉≪ 1, where 〈inlineGraphic alt="inline image" href="urn:x-wiley:0956540X:GJI757:GJI_757_mu2" location="equation/GJI_757_mu2.gif"/〉 is the root-mean-square degree of the phase-velocity perturbation δc, and l is the degree of the equivalent mode nSl or nTl. This condition, which is independent of the number of orbits, is obtained by consideration of the Fresnel area along the surface-wave ray path between the source and receiver. We assess the accuracy of surface-wave ray theory by comparing the phase, arrival angle and amplitude anomalies obtained using the JWKB approximation with the corresponding quantities measured using ‘ground-truth’ synthetic coupled-mode seismograms on models of varying roughness. The JWKB results agree well with the coupled-mode results for model S12_WM13; on a contrived model with slightly rougher variations, however, the agreement deteriorates as the condition 〈inlineGraphic alt="inline image" href="urn:x-wiley:0956540X:GJI757:GJI_757_mu3" location="equation/GJI_757_mu3.gif"/〉≪ 1 is less well satisfied. The misfit of the ray approximation, which is dependent upon the quantity 〈inlineGraphic alt="inline image" href="urn:x-wiley:0956540X:GJI757:GJI_757_mu4" location="equation/GJI_757_mu4.gif"/〉, can be attributed to diffraction and other finite-frequency effects within the Fresnel area along the ray path; these effects are ignored by the JWKB theory but are fully accounted for by the coupled-mode summation. The wavefront smoothing produced by this Fresnel-area averaging limits the resolution of surface-wave inversion studies based upon the JWKB approximation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1995.tb06888.x
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  • 5
    Electronic Resource
    Electronic Resource
    Mode-sum to ray-sum transformation in a spherical and an aspherical earth (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 126 (1996), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: We complete our series of studies on the duality between relatively high-frequency normal modes and seismic body waves by explicitly converting the normal-mode summation expressing the elastic response of a spherically symmetric earth model into a body-wave summation. The procedures in this conversion are discussed in detail for a crust-stripped version of model 1066A with a solid mantle, a fluid outer core and a solid inner core. The resulting body-wave responses, the Green tensors representing the various body waves, are in agreement with the well-documented results obtained using geometrical ray theory.The results derived for the spherically symmetric earth model are then used to obtain the first-order body-wave Green tensors in a laterally heterogeneous earth model based upon the Born approximation. The first-order effect of the coupling between normal-mode multiplets is shown to be equivalent to the single scattering of seismic body waves by the lateral heterogeneity, as expected from numerous previous studies. We present compact expressions for the scattering matrix and the body-wave Frechet kernels. A few numerical examples of the Frechet kernels for monochromatic body waves are also provided.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1996.tb05299.x
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  • 6
    Electronic Resource
    Electronic Resource
    Asymptotic normal modes of the Earth—III. Fréchet kernel and group velocity (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 122 (1995), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: A comprehensive study of the Fréchet kernels and group velocities of the Earth's normal modes is conducted based upon the asymptotic eigenfrequency and eigenfunction analyses that we developed previously. Two different approaches, which employ the eigenfunctions or eigenfrequency equations, yield asymptotically equivalent results for the Fréchet kernels and group velocities. The latter approach is considerably simpler, since the need to specify the normal-mode eigenfunctions as well as their radial derivatives is removed, so that the Fréchet kernels and group velocities can be obtained from knowledge of the asymptotic eigenfrequencies only.The asymptotic analyses are discussed for all possible ray parameter regimes and ray-path combinations within a crustless version of the earth model 1066A with two discontinuities: a core-mantle boundary and an inner core boundary. The exact and asymptotic numerical results for the Fréchet kernels and group velocities are compared for such a model. The comparison shows that the asymptotic Fréchet kernels and group velocities are very accurate. The accuracy is better for toroidal modes and relatively high-frequency spheroidal modes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1995.tb03555.x
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  • 7
    Electronic Resource
    Electronic Resource
    Asymptotic normal modes of the Earth—II. Eigenfunctions (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 121 (1995), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: We derive asymptotic expressions for the toroidal- and spheroidal-mode eigenfunctions of a SNREI earth model with two discontinuities. The ray-theoretical wavefunctions of high-frequency SH and P-SV waves are expressed in terms of scalar potentials for which WKBJ solutions are readily available. The normal-mode eigenfunctions are then derived from the wavefunctions using the correspondence between the toroidal modes and SH waves, and the spheroidal modes and P-SV waves. Both oscillatory and evanescent solutions are included to enhance the accuracy of the asymptotic eigenfunctions in the vicinity of the inner-core and core-mantle boundaries. The analytic expressions of the asymptotic eigenfunctions only involve simple sine, cosine and exponential functions which can be easily manipulated and evaluated, making the asymptotic eigenfunctions very useful for further normal-mode studies. Numerical comparison of the asymptotic and exact eigenfunctions shows that there is an excellent agreement for a crustless version of earth model 1066A. A mistake in our previous asymptotic eigenfrequency analysis, which ignored the geometrical spreading effect, has been corrected. The consistency between the asymptotic eigenfrequency and eigenfunction analyses is also addressed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1995.tb05736.x
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  • 8
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    Mode-sum to ray-sum transformation in a spherical and an aspherical earth (1996)
    Oxford University Press
    Details
    Publication Date: 1996-08-01
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Royal Astronomical Society.
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    PAPER CURRENT
  • 9
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    Theoretical Global Seismology (1999)
    American Institute of Physics
    Details
    Publication Date: 1999-08-01
    Print ISSN: 0031-9228
    Electronic ISSN: 1945-0699
    Topics: Physics
    Published by American Institute of Physics
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  • 10
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    Latest spin on the core (1999)
    Springer Nature
    Details
    Publication Date: 1999-11-01
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Springer Nature
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    PAPER CURRENT
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