2002 Fiscal Year Final Research Report Summary
A study on the mantle electrical conductivity structure beneath the eastern edge of continental Asia
| Project/Area Number |
12573004
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 海外学術 |
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| Research Field |
固体地球物理学
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| Research Institution | The University of Tokyo |
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Principal Investigator |
UTADA Hisasi Earthquake Research Institute, Professor, 地震研究所, 教授 (70134632)
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| Co-Investigator(Kenkyū-buntansha) |
YUMOTO Kiyofumi Graduate School of Sciences, Kyushu University, Professor, 大学院・理学研究院, 教授 (20125686)
SHIMIZU Hisayoshi Earthquake Research Institute, Research Associate, 地震研究所, 助手 (70302619)
UYESHIMA Makoto Earthquake Research Institute, Associate Professor, 地震研究所, 助教授 (70242154)
GOTO Tadanori Japan Marine Science and Technology Center, Scientist, 研究員 (90303685)
FUJII Ikuko Magnetic Observatory, Japan Meteorological Agency, Researcher, 地磁気観測所, 研究官
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| Project Period (FY) |
2000 – 2002
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| Keywords | Eastern Asia / Long-term observation / Electrical conductivity / Network-MT method / Mantle / Transition zone / NE district of China / Frimolsky region |
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| Research Abstract |
This three-year research project aimed to make a detailed investigation of the electrical conductivity distribution in the deep mantle beneath region including the NE district of China and the Primorsky region of Russia, where active Quaternary volcanoes widely distribute. For this purpose we carried out long-term observation of natural electromagnetic field variations in the study area in cooperation with Chinese and Russian scientists. Network-MT method developed by the present investigators were employed to reveal the deep structure in the mantle.
In 2001, electric field variation data from the network in Jilin province and magnetic field data at Changchun were analyzed and inverted into one-dimensional (depth only dependent) conductivity model. Resulting conductivity profiles were compared to those of other studies from North America and Hawaii. It was found that no significant difference exists in the conductivity of the upper mantle and the uppermost lower mantle between the present and past results, while the mantle transition zone of the present result showed higher conductivity by nearly one order of magnitude. A preliminary report was published in Geophysical Research Letters (Ichiki et al., 2001).
In 2002, Network-MT experiment was shifted to the south in Liaoning province. Response functions were also obtained by using electric field data from 3 lines and magnetic field data at Changchun up to the period of several, and were individually inverted into one-dimensional conductivity profiles. The results were compared with profiles from Jilin province, and were found to be slightly more resistive in the mantle transition zone. However, it was concluded that additional experiments in wider area are necessary to resolve whether this difference is only apparent or reflects lateral variation of conductivity at depths. This result is going to be published in Geophysical Research Letters.
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[Publications] Ichiki, M., Uyeshima, M., Utada, H., Zhao, G., and Tang, J., and Ma, M.: "Upper mantle conductivity structure of the back-arc region beneath northeastern China"Geophys. Res. Lett.. 28. 3773-3776 (2001)
Description
「研究成果報告書概要(欧文)」より
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