Ray-theoretical relations between intrinsic and apparent dissipation factors in the Earth期刊界 All Journals 搜尽天下杂志传播学术成果专业期刊搜索期刊信息化学术搜索

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Ray-theoretical relations between intrinsic and apparent dissipation factors in the Earth

Authors:	Toshikazu Odaka

Institution:	Earthquake Research Institute. University of Tokyo, Bunkyo-ku, Tokyo 113, Japan

Abstract:	Summary. A ray-theoretical approach is successfully employed for obtaining the relations between the intrinsic dissipation factors of P - and S -waves, Q _α and Q _β, and the apparent dissipation factors of toroidal and spheroidal oscillations, Q _Tor and Q _SphThese are given in quite simple forms and are expressed, to zero-order approximatiom which neglects the effect of reflection of waves at an interface and/or at a free surface), as where α and β are the P - and S -wave velocities and the integrals are evaluated long the surface to surface P - and S -rays. Some numerical comparisons support the validity of these formulae for higher modes of toroidal and radial oscillations of a realistic earth model. A first-order approximation reveals that the existence of a discontinuity in an earth induces a systematic fluctuation in normal-mode Q values for any given phase velocity as a function of frequency (or radial mode number).

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