Vector-scattering of elastic waves by directional structural space gradients |
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| Authors: | Ari Ben-Menahem |
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| Institution: | (1) Department of Applied Mathematics, The Weizmann Institute of Science, 76100 Rehovot, Israel |
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| Abstract: | A nonstochastic and noniterative theory of vector scattering in inhomogeneous media is presented. The elastodynamic vector wave-equation for 3D inhomogeneous media is solved for a weak heterogeneity at the high-frequency region. It is shown that there exists a forward scattered field which decays slowly along the source-receiver path. Its rate of attenuation depends on the azimuth of the path relative to the direction of the inhomogeneity, but is independent of frequency. The Green's tensor for the above regime is derived in closed form and leads to the quantification of fields of dipolar sources in weak inhomogeneous media. The inhomogeneity at the source creates a source-induced scattering (in addition to path-scattering) having a radiation-pattern that bears the signature of the source. The availability of the analytic Green's tensor, in conjunction with the Huygens-Kirchhoff-Helmholtz formalism, opens new ways to calculate the scattered fields due to various structural inhomogeneities applicable to exploration and earthquake seismology. The theoretical results of this study point to the conclusion that the scalar wave approximation may not always be valid for the propagation of seismic waves in the earth's lithosphere. |
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| Keywords: | Scattering elastic waves Green's tensor inhomogeneous media attenuation |
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