Study of Attenuation Mechanism of Seismic Waves in the Crust

地震波在地壳中的衰减机制研究

• 批准号: 05680355
• 负责人: SATO Haruo
• 金额: $ 1.28万
• 依托单位: Tohoku University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1993
• 资助国家: 日本
• 起止时间: 1993 至 1994
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-05680355/
• 关键词: Scattering; Attenuation; Crust; Seismic waves; 地殻波; エンベロープ

There are three major contributions for the quantitative prediction of seismic ground motion : source ; path, and site. Here we focused on the second and the third subjects : scattering and attenuation as a path effect ; site amplification study of hard rocks as a site effect. Based on the filed observation at Ashio, Tochigi prefecture, we have clarified the frequency dependent amplification factors of both P and S waves at hard rocks as granite (Yoshimoto et al., 1993b). Developing the conventional coda normalization method, we first measured the frequency dependence of both P and S wave attenuation in the Kanto area (Yoshimoto et al., 1993a). We have newly developed a mathematical formulation of the energy propagation through scattering and attenuation media based on the energy transport theory (Sato, 1994a, 1994b, 1995b). This formalism adopt any type of no-isotropic scattering, and is useful for the study of high frequency seismogram envelopes. The numerical synthesis based on this formulation well explains the spatially uniform distribution of energy density (1995b). This method is applied to seismograms obtained at Onagawa, Miyagi prefecture. The estimated S wave attenuation factor is proportional to frequency, and the contribution ratio of scattering loss to the total attenuation, the seismic albedo, is small as about 0.25. If we increase the forward scattering, the seismic albedo becomes twice. Based on the analysis of seismogram envelopes, we found that the randomness of the lithosphere is much larger under the west of the volcanic front compared with that under the east in Kanto-Tokai area, Japan (Obara and Sato, 1995a)

对地震地面运动的定量预测有三个主要贡献：来源；路径和站点。在这里，我们专注于第二个和第三个主题：散射和衰减作为路径效应；硬岩作为现场效应的现场扩增研究。基于在tochigi县的Ashio上的观察结果，我们阐明了硬岩为花岗岩的P和S波的频率依赖性扩增因子（Yoshimoto等，1993b）。开发常规的尾巴归一化方法，我们首先测量了关东地区P和S波衰减的频率依赖性（Yoshimoto等，1993a）。我们通过基于能量运输理论的散射和衰减介质，新开发了能量传播的数学表述（Sato，1994a，1994b，1995b）。这种形式主义采用任何类型的无偏射散射，对于研究高频地震图包络的研究很有用。基于此公式的数值合成很好地解释了能量密度的空间均匀分布（1995b）。该方法应用于在宫川县Onagawa获得的地震图。估计的S波衰减因子与频率成正比，并且散射损失与总衰减的贡献比，地震反照率大约为0.25。如果我们增加向前的散射，地震反照率将变为两次。基于对地震图信封的分析，我们发现岩石圈的随机性在火山沿西部的西部与日本的关东 - 托基地区的东部相比要大得多（Obara and Sato，1995a）

项目成果

Sato,H.: "Formulation of multiple non-isotropic scatering process in two dimensional space on the basis of energy transport theory" Geophysical Journal International. (印刷中). (1994)

Sato, H.：“基于能量传输理论的二维空间中多个非各向同性过程的公式”，国际地球物理杂志（1994 年）。

Obara, K., and H.Sato: "Regional differences of random inhomogeneities around the volcanic front in the Kanto-Tokai area, Japan, revealed from the broadening of S wave seismogram envelopes" J.Geophys.Res.100. 2103-2121 (1995)

Obara, K. 和 H.Sato：“日本关东-东海地区火山前缘周围随机不均匀性的区域差异，从 S 波地震图包络的扩大中揭示”J.Geophys.Res.100。

Sato,H.: "Multiple isotropic scattering model including P-S conversions for the seismogram envelope formation" Geoghysical Journal International. 117. 487-494 (1994)

Sato,H.：“多重各向同性散射模型，包括用于地震图包络形成的 P-S 转换”《国际地球物理学杂志》。

Obara,H. and H.Sato: "Regional differences of random inhomogeneities around the volcanic front in the Kanto-Tokai area,Japan,revealed from the broadening of S wave seismogram envelopes" Journal of Geophysical Research. 100. 2103-2121 (1995)

小原，H.

Sato, H.: "Formulation of the multiple non-isotropic scattering process in 2-D space on the basis of energy transport theory" Geophys.J.Int.117. 722-732 (1994)

Sato, H.：“基于能量传输理论的二维空间中多重非各向同性散射过程的公式化”Geophys.J.Int.117。