| Project/Area Number |
09640502
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
固体地球物理学
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| Research Institution | TOHOKU UNIVERSITY |
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Principal Investigator |
SATO Haruo Tohoku University Graduate School of Science, Dept.of Geophysics, Professor., 大学院・理学研究科, 教授 (80225987)
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| Co-Investigator(Kenkyū-buntansha) |
NAKAHARA Hisashi Tohoku University, Graduate School of Science, Dept.of Geophysics, Research Asso, 大学院・理学研究科, 助手 (20302078)
YOSHIMOTO Kazuo Tohoku University Graduate School of Science, Dept.of Geophysics, Research Assoc, 大学院・理学研究科, 助手 (10281966)
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| Project Period (FY) |
1997 – 1998
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| Project Status |
Completed (Fiscal Year 1998)
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| Budget Amount *help |
¥2,400,000 (Direct Cost: ¥2,400,000)
Fiscal Year 1998: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1997: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Keywords | Coda waves / Heterogeneous structure / Source process / Radiative transfer theory / Envelope analysis |
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| Research Abstract |
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.
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