caa a22 4500 477047939 CHVBK 20180405111335.0 cr unu---uuuuu 170330e19961001xx s 000 0 eng 10.1007/BF01089697 doi (NATIONALLICENCE)springer-10.1007/BF01089697 Scattering of P and S waves by a spherically symmetric inclusion [Elektronische Daten] [Valeri Korneev, Lane Johnson] Scattering of an arbitrary elastic wave incident upon a spherically symmetric inclusion is considered and solutions are developed in terms of the spherical vector system of Petrashen, which produces results in terms of displacements rather than displacement potentials and in a form suitable for accurate numerical computations. Analytical expressions for canonical scattering coefficients are obtained for both the cases of incidentP waves and incidentS waves. Calculations of energy flux in the scattered waves lead to elastic optical theorems for bothP andS waves, which relate the scattering cross sections to the amplitude of the scattered fields in the forward direction. The properties of the solutions for a homogeneous elastic sphere, a sphere filled by fluid, and a spherical cavity are illustrated with scattering cross sections that demonstrate important differences between these types of obstacles. A general result is that the frequency dependence of the scattering is defined by the wavelength of the scattered wave rather than the wavelength of the incident wave. This is consistent with the finding that the intensity of theP→S scattering is generally much stronger than theS→P scattering. When averaged over all scattering angles, the mean intensity of theP→S converted waves is2V p 2 /V s 4 times the mean intensity of theS→P converted waves, and this ratio is independent of frequency. The exact solutions reduce to simple and easily used expressions in the case of the low frequency (Rayleigh) approximation and the low contrast (Rayleigh-Born) approximation. The case of energy absorbing inclusions can also be obtained by assigning complex values to the elastic parameters, which leads to the result that an increase in attenuation within the inclusion causes an increased scattering cross section with a marked preference for scatteredS waves. The complete generality of the results is demonstrated by showing waves scattered by the earth's core in the time domain, an example of high-frequency scattering that reveals a very complex relationship between geometrical arrivals and diffracted waves. Birkhäuser Verlag, 1996 Elastic waves nationallicence sphere nationallicence scattering nationallicence diffraction nationallicence Korneev Valeri Department of Geology and Geophysics, and Center for Computational Seismology, Lawrence Berkeley Laboratory, University of California, 94720, Berkeley, California, U.S.A. aut Johnson Lane aut pure and applied geophysics Birkhäuser-Verlag 147/4(1996-10-01), 675-718 0033-4553 147:4<675 1996 147 24 https://doi.org/10.1007/BF01089697 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF01089697 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Korneev Valeri Department of Geology and Geophysics, and Center for Computational Seismology, Lawrence Berkeley Laboratory, University of California, 94720, Berkeley, California, U.S.A aut NATIONALLICENCE 700 1- Johnson Lane aut NATIONALLICENCE 773 0- pure and applied geophysics Birkhäuser-Verlag 147/4(1996-10-01), 675-718 0033-4553 147:4<675 1996 147 24 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer