2002 Fiscal Year Final Research Report Summary
Conductivity structure around seismogenic layer beneath the Chugoku and Shikoku districts
| Project/Area Number |
13440133
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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 | 一般 |
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| Research Field |
固体地球物理学
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| Research Institution | Kobe University |
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Principal Investigator |
YAMAGUCHI Satoru Kobe University, Faculty of Science Lecturer, 理学部, 講師 (70191228)
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| Co-Investigator(Kenkyū-buntansha) |
OSHIMAN Naoto Kyoto University, Disaster Prevention Research Institute Professor, 防災研究所, 教授 (70185255)
SHIOZAKI Ichiro Tottori University, Faculty of Engineering Associate Professor, 工学部, 助教授 (80221290)
MURAKAMI Hideki Kochi University, Faculty of Science Associate Professor, 理学部, 助教授 (10166259)
SHIMA Nobukazu Kobe University, Research Center for Inland Seas Associate Professor, 内海域機能教育研究センター, 助教授 (30270862)
UYESHIMA Makoto Tokyo University, Earthquake Research Institute Associate Professor, 地震研究所, 助教授 (70242154)
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| Project Period (FY) |
2001 – 2002
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| Keywords | Philippine Sea Plate / South-western Japan arc / conductivity structure / seismogenic layer |
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| Research Abstract |
We delineated the Philippine Sea plate beneath the South-western Japan arc using the electro-magnetic method in this study.
The Network-MT method is one of the magnetotelluric methods and it is suitable for surveying a conductivity structure beneath a wide area and to a deep portion. We applied the method in Chugoku and Shikoku district to reveal a subsurface structure beneath the South-west Japan arc. We focused on the where and how does the Philippine Sea Plate exist. The first reason is that a location of The Philippine Sea plate is most important factor to controlled occurrences of earthquakes, because the cold and rigid plate makes large influence on a thermal state and/or a distribution of seismic-wave velocity. Second reason is that it is hard to decide a location of the plate using only seismic methods.
The precise 2-dimensional conductivity model was established. This model is characterized by following points.
1) North dipping resistive layer (> 500Ω・m) exists beneath both Chugoku and Shikoku districts. The upper depth of the resistive layer is 20km, 30km beneath the southern and northern part of the Shikoku district, and 40km, 60km beneath the southern and northern part of the Chugoku district, respectively. 2) Conductive layer (~100Ω・m) exists beneath the north dipping resistive layer. 3) Highly conductive layer is found at 40km-depth beneath the northern most part of the Chugoku district. We interpreted the north dipping resistive layer is the Philippine Sea plate.
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