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Study on medium heterogeneity beneath island arcs based on the analysis of seismic wave scattering

基于地震波散射分析的岛弧下介质非均质性研究

基本信息

批准号：
17540389
负责人：
SATO Haruo
金额：
$ 2.3万
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：
2005
资助国家：
日本
起止时间：
2005 至 2006
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-17540389/
关键词：
Seismic wave solid earth crust mantle heterogeneous structure scattering coda waves island arc 島弧

项目摘要

Source duration times of microearthquakes are short; however, apparent duration times of S wave envelopes increase with travel distance increasing caused by scattering due to medium inhomogeneities. We clarified that the medium inhomogeneity is stronger in the back-arc side of the volcanic front compared with that in the fore-arc side in Japan arc. In this research, extending this idea, we carefully measured the relation between the S-wave peak delay from the onset and the ray path. We also developed the envelope synthesis in random elastic media as the mathematical foundation for these analyses. We find that the peak delays are larger for ray paths traveling beneath Quaternary volcanoes than those for ray paths traveling between Quaternary volcanoes in northern Japan. That is, the medium inhomogeneity is stronger beneath Quaternary volcanoes, but the medium is homogeneous between them. Interpreting the partition of energy of teleseismic P and P coda waves into the transverse component as a measure of medium heterogeneity, we classified the lithospheric heterogeneity in the world : the medium heterogeneity is large at plate collision, zones and subduction zones; however, it is small in continents. On the basis of the Markov approximation we have developed the direct envelope synthesis of vector waves in random elastic media. We have successfully formulated the envelope syntheses for both the incidence of a plane wavelet and the radiation from a point source in 2-D and 3-D cases. Especially in 2-D, we have confirmed the validity by using the finite difference simulations.

微震震源持续时间短；然而，S波包络线的表观持续时间随着介质不均匀性散射引起的行进距离增加而增加。我们阐明，与日本弧的弧前侧相比，火山前缘弧后侧的介质不均匀性更强。在这项研究中，扩展了这个想法，我们仔细测量了横波峰值延迟与射线路径之间的关系。我们还开发了随机弹性介质中的包络合成作为这些分析的数学基础。我们发现，在第四纪火山下方传播的射线路径的峰值延迟比在日本北部第四纪火山之间传播的射线路径的峰值延迟更大。即第四纪火山下方的介质不均匀性较强，但火山之间的介质是均匀的。将远震P波和P尾波能量分配到横向分量作为介质非均质性的度量，对世界岩石圈非均质性进行了分类：板块碰撞带、俯冲带介质非均质性较大；板块碰撞带、俯冲带介质非均质性较大；然而，在大陆上它很小。在马尔可夫近似的基础上，我们开发了随机弹性介质中矢量波的直接包络合成。我们已经成功地制定了 2D 和 3D 情况下平面小波的入射和点源辐射的包络合成。特别是在二维方面，我们通过有限差分模拟证实了其有效性。

项目成果

期刊论文数量（41）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Temporal changes in seismic velocity of the crust around Iwate volcano, Japan, as inferred from analyses of repeated active seismic experiment data from 1998 to 2003

1998—2003年重复主动地震实验数据分析日本岩手火山周边地壳地震速度随时间变化

DOI：
发表时间：
2005
期刊：
Earth Planets Space 57
影响因子：
0
作者：
Nishimura;T.;S.Tanaka;T.Yamawakil;H.Yamamoto;T.Sano;M.Sato;H.Nakahara;N.Uchidal.;S.Hori;H.Sato
通讯作者：
H.Sato

Synthesis of vector wave envelopes in three-dimensional random elastic media characterized by a Gaussian autocorrelation function based on the Markov approximation : Spherical wave case

基于马尔可夫近似的高斯自相关函数表征的三维随机弹性介质中矢量波包络的合成：球面波情况