2007 Fiscal Year Final Research Report Summary
Anisotropic structure in detail using broadband seismic waveform data and waveform inersion
| Project/Area Number |
17540392
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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 |
Solid earth and planetary physics
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| Research Institution | The University of Tokyo |
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Principal Investigator |
GELLER Robert J. The University of Tokyo, Graduate School of Science, Professor (40170154)
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| Co-Investigator(Kenkyū-buntansha) |
TAKEUCHI Nozomu The University of Tokyo, Earthquake Research Institute, Assistant Researcher (90313048)
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| Project Period (FY) |
2005 – 2007
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| Keywords | Waveform inversion / Transition zone / D"layer / Seismic anisotropy / Direct Solution Method / Partial derivatives |
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| Research Abstract |
The aim of this study is to obtain 3-D seismic anisotropic velocity structure of the Earth in detail. Conducting waveform inversion by using broadband waveforms themselves, which include both body waves and surface waves, this study is aimed to obtain detailed 3-D anisotropic model with high resolution and high accuracy. As the waveform inversion (using body-wave waveforms, especially) is a new study world-widely, this study started first in settling the methodology for this inversion (and also realizing it in terms of software): we now are obtaining interesting results (1D structure models), using the methodology for D" layers beneath several regions in the world and for mantle transition zone beneath several subregions in and around Japan after these 3 years. Our models of D" layer beneath several regions showed. possible evidence for the double crossing phase transition hypothesis (Hernlund, et al., 2005) within the layer first in the world (Kawai, et al., 2007ab, Konishi, et al., 2007) and also examine the ubiquity of the double-crossing phase transition. Our study for 1-D SH velocity models of mantle transition zone beneath 4 very localized subregions in the Northwestern Pacific found obvious amplitude difference between the observed waveforms and the synthetic waveforms for the initial model and tried simultaneously to invert for anelastic attenuation Q parameters as well. In this study we introduced efficient and accurate formulation of partial derivatives with respect to Q and developed software for Q partial derivatives. We concluded that systematically Q is lower than PREM in and around Japan (Fuji, et al., 2007). We also developed software for calculating 2-D synthetic seismograms using optimally accurate for 2-D finite difference method describe in Takeuchi & Geller (2000, PEPI). This software can calculate for media which include arbitrary discontinuities.
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Research Products
(44 results)
