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Study of the inhomogeneous structure of the earth from the analysis of scattering phenomena of broad band seismic waves

从宽带地震波散射现象分析研究地球的不均匀结构

基本信息

批准号：
15540399
负责人：
SATO Haruo
金额：
$ 2.05万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2004
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15540399/
关键词：
Interior of solid earth seismic waves inhomogeneity scattering lithosphere random media 地球内部構造

项目摘要

Study of inhomogeneous structure of the earth medium is important for understanding the evolution process of the earth. We performed three seismological studies as follows : 1.Small-scale inhomogeneity of the lithosphere based on the analysis of high-frequency seismic waves : Combining the radiative transfer theory and the Markov approximation, we constructed a hybrid model for the synthesis of the whole scalar-wave envelope in 2-D random media. Extending the Markov approximation for vector wave propagation in 2-D elastic random media, we proposed a new synthesis model, which quantitatively explains envelopes synthesized by the finite difference simulation. Scattering due to random inhomogeneity well explains the peak amplitude decay and the envelope broadening observed. Strong scattering beneath Quaternary volcanoes was revealed from the envelope broadening analysis in Tohoku district. We made the depth profile of the Moho and the subducting Philippine-sea plate in Chugoku-Shikoku dis … More trict by using the receiver function method. 2.Scattering characteristics in the mantle from the analysis of ScS phase in intermediate periods : Analyzing wave envelopes around the ScS phase of regional earthquakes by using the isotropic scattering model based on PREM, we first estimated quantitatively the scattering coefficient in the mantle for periods from 4 to 10 s. 3.Envelope analysis of long period Rayleigh waves : We analyzed vertical-component seismograms of large earthquakes in long periods recorded by IRIS and F-net. The array analysis revealed that the fundamental mode Rayleigh waves dominate early lapse times but higher modes dominate as lapse time increases because of small attenuation in the lower mantle. We find that the coda attenuation factor directly represents the attenuation factor in the lower mantle. Clarifying the scattering characteristics between Rayleigh waves and body waves in random elastic half media, we established the solid base for the envelope synthesis in long periods. Less

研究地球介质的非均质结构对于理解地球的演化过程具有重要意义。我们进行了以下三项地震学研究： 1.基于高频地震波分析的岩石圈小尺度不均匀性：结合辐射传输理论和马尔可夫近似，构建了二维随机介质中全标量波包络合成的混合模型。扩展二维弹性随机介质中矢量波传播的马尔可夫近似，我们提出了一种新的合成模型，该模型定量地解释了通过有限差分模拟合成的包络。由于随机不均匀性引起的散射很好地解释了观察到的峰值振幅衰减和包络变宽。东北地区的包络线展宽分析揭示了第四纪火山下方的强烈散射。利用接收函数法，对中国-四国地区莫霍面和俯冲菲律宾海板块的深度剖面进行了精确的绘制。 2.中期ScS相分析地幔中的散射特征：利用基于PREM的各向同性散射模型对区域地震ScS相周围的波包络进行分析，首先定量估计了4~10s周期地幔中的散射系数。 3.长周期瑞利波包络分析：我们分析了IRIS和F-net记录的长周期大地震的垂直分量地震图。阵列分析表明，基本模式瑞利波在早期的流逝时间中占主导地位，但随着流逝时间的增加，由于下地幔中的衰减较小，更高的模式占主导地位。我们发现尾波衰减因子直接代表下地幔的衰减因子。阐明了随机弹性半介质中瑞利波和体波的散射特性，为长周期包络合成奠定了坚实的基础。较少的