| Project/Area Number |
08404024
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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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 | the University of Tokyo |
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Principal Investigator |
TAMAKI Kensaku Ocean Research Institute, the University of Tokyo, Professor, 海洋研究所, 教授 (50188421)
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| Co-Investigator(Kenkyū-buntansha) |
ISEZAKI Nobuhiro Faculty of Science, Chiba University, Professor, 理学部, 教授 (60107943)
YAMANO Makoto Earthquake Research Institute, the University of Tokyo, Associate Professor, 地震研究所, 助教授 (60191368)
NAKANISHI Masao Ocean Research Institute, the University of Tokyo, Research Associate, 海洋研究所, 助手 (80222165)
ISHII Teruaki Ocean Research Institute, the University of Tokyo, Associate Professor, 海洋研究所, 助教授 (80111582)
FUJIMOTO Hiromi Ocean Research Institute, the University of Tokyo, Associate Professor, 海洋研究所, 助教授 (50107455)
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| Project Period (FY) |
1996 – 1998
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| Keywords | mid-oceanic ridges / crust / tectonics / geomagnetism |
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| Research Abstract |
The objective of this program is to understand the sea floor spreadingtectonics, volcanism, earthquake activities, and hydrothermal activites of the Southwestern Indian Ridge, an ultraslow spreding system. The FUJI cruise (French-UK-Japan InterRidge cruise) was conducted from October 7 to November 3, 1997 at the eastern part of the Southwestern Ridge. The main parts of the measurements are TOBI deep-tow sidescan sonnar observation (30kHz, 6km swath) and the ocean bottom seismometer observation for the crustal structure and earthquake activities. Two first order segments with the length of 200 km each were selected for along axes towing. One 100km*100km box was set for the deep-tow box survey including offaxis part. The TOBI sidescan image well displayed the detail of volcanic features and fault distribution. The principal results of the FUJI cruise are as follows. (1) Intensive heterogeneity of the crusts were suggested by focused magmatism in the center of the segment. (2) A 70 km long non volcanic segment with a complex fault pattern was identified, although understanding of spreading mechanism of this part needs more survey in this area. (3) Strong contrast of sea bottom features between the offaxes parts of a segment is observed as the northern flank with volcanic construction and as the southern flank with pausity of volcanic construction. (4) Large dtachmen faults are observed suggesitng these type of faults have principal role on the spreading tectonics here. (5) Intensive focused seismic activity was observed y OBS at one of the largest segemts in the area.
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