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エネルギー輸送理論に基づく高周波数地震波形エンベロープの研究

基于能量传输理论的高频地震波形包络研究

基本信息

批准号：
09640502
负责人：
SATO Haruo
金额：
$ 1.54万
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：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09640502/
关键词：
Coda waves Heterogeneous structure Source process Radiative transfer theory Envelope analysis

项目摘要

High-frequency seismograms of local earthquakes are composed of incoherent scattered waves from distributed random heterogeneities in the Earth. We can quantitatively measure the random heterogeneity from the characteristics of seismogram envelopes, For the study of high-frequency energy propagation, the radiative transfer theory is know to be very useful ; however, this theory was too simple to analyze complex seismograms. In 1997, we have developed the radiative transfer theory in order to adopt nonspherical source radiation, which describes realistic seismic source. Applying this theory to strong motion records of the 1994 far-east off-Sanriku earthquake, we estimated the spatial distribution of high-frequency energy radiation from the earthquake fault. The high-frequency radiation was found to be the strongest at the end of rupture, which is different from the location of the largest fault-slip. In 1998, we have developed the radiative transfer theory to adopt realistic velocity structure, which increases with depth. Applying the developed theory to the 1995 Hyogo-ken Nanbu (Kobe) earthquake, we found a few strong-radiation spots on the fault plane. Thus, we have presented the usefulness of the radiative transfer theory in the inversion for the source radiation process. In addition, we have installed two sets of small seismic arrays at Tono and Sanriku in the Tohoku district in order to analyze the spectra of the velocity structure of the earth medium. The head investigator published a textbook which introduces scattering and propagation of high-frequency seismic waves in the heterogeneous Earth medium.

局部地震的高频地震图是由地球上分布的随机非均质性的非相干散射波组成的。我们可以从地震记录包络的特征来定量地测量随机非均质性，对于高频能量传播的研究，辐射传输理论是非常有用的，但是这个理论太简单了，不能分析复杂的地震记录。1997年，为了采用描述现实震源的非球面震源辐射，我们发展了辐射传输理论。将这一理论应用于1994年远东三陆地震的强震记录，估算了地震断层高频能量辐射的空间分布。高频辐射在破裂末期最强，与最大断层滑动的位置不同。1998年，我们发展了辐射传输理论，采用了随深度增加的真实速度结构。将所发展的理论应用于1995年兵库县南部(神户)地震，在断裂面上发现了几个强辐射点。因此，我们提出了辐射传递理论在源辐射过程反演中的作用。此外，我们还在东北地区的Tono和Sanriku安装了两套小型地震台阵，以分析地球介质的速度结构频谱。首席研究员出版了一本教科书，介绍了高频地震波在非均匀地球介质中的散射和传播。