Polarization and amplitude attributes of reflected plane and spherical waves |
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Authors: | Jinjun Jiang,Graham Baird,& Dane Blair |
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Affiliation: | ICI Explosives, PO Box 497, Kalgoorlie, WA 6430, Australia,;W A School of Mines, PMB 22, Kalgoorlie WA 6430, Australia,;ICI Explosives, PO Box 196, Kurri Kurri, NSW 2327, Australia |
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Abstract: | The characteristics of a reflected spherical wave at a free surface are investigated by numerical methods; in particular, the polarization angles and amplitude coefficients of a reflected spherical wave are studied. The classical case of the reflection of a plane P wave from a free surface is revisited in order to establish our terminology, and the classical results are recast in a way which is more suited for the study undertaken. The polarization angle of a plane P wave, for a given angle of incidence, is shown to be 90° minus twice the angle of reflection of the reflected S wave. For a Poisson's ratio less than 1/3, there is a non-normal incident angle for which both amplification coefficients are 2 precisely; for this incident angle the direction of the particle motion at the free surface is also the direction of the incident wave. For a wave emanating from a spherical source, the polarization angle, for all angles of incidence, is always less than, or equal to, the polarization angle of a plane P wave. The vector amplification coefficient of a spherical wave, for all angles of incidence, is always greater than the vector amplification coefficient of a plane P wave. As expected, the results for a spherical wave approach the results for a plane P wave in the far field. Furthermore, there was a good agreement between the theoretical modelling and the numerical modelling using the dynamic finite element method (DFEM). |
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Keywords: | amplitude coefficients polarization angles P waves reflection spherical waves |
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