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タイトル: The Orbit of Surface Waves in Weakly Anisotropic Media
その他のタイトル: 弱い異方性媒質における表面波の軌道
著者: Momoi, Takao
著者(別言語): 桃井, 高夫
発行日: 1991年12月27日
出版者: 東京大学地震研究所
掲載誌情報: 東京大学地震研究所彙報. 第66冊第3号, 1991.12.27, pp. 475-495
抄録: Surface waves in the weakly anisotropic media are discussed focusing attention on the relation between the Rayleigh wave orbit and its velocity and stability. The wave number in weakly anisotropic media involves imaginary terms. Rayleigh waves in an anisotropic medium always face a stability problem due to the imaginary term. In weakly anisotropic media, the longitudinal and vertical components (u, w) compose quasi-Rayleigh waves which resemble Rayleigh waves in an isotropic medium. The horizontally transverse components (v) behave as quasi-Love waves which are independent of the former quasi-Rayleigh waves with respect to the elastic coefficients. The quasi-Love waves then decrease in amplitude with depth in the material. The increase (or decrease) of Rayleigh wave velocity due to anisotropy of the media leads to shrinkage (or expansion) of quasi-Rayleigh wave orbit. In this case, the vertical component of the Rayleigh wave is more sensitive than the horizontal one to anisotropy. The Rayleigh wave orbit is quite sensitive to the velocity change due to anisotropy. For instance, a one percent velocity increase causes about 10 percent increase in the Rayleigh wave orbit size (major and/or minor axis). When the quasi-Rayleigh waves are stable (or unstable), the Rayleigh wave orbit axis tilts backward (or forward). When a Rayleigh wave increases (decreases) in amplitude by 10 or 20 percent after traveling the distance of the wavelength, the inclination angle of the orbit at the surface is in the range 5~30 degrees.
URI: http://hdl.handle.net/2261/13089
ISSN: 00408972


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