| Project/Area Number |
12309002
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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 |
広領域
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| Research Institution | The University of Tokyo |
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Principal Investigator |
SATO Hiroshi The Univ. of Tokyo, Earthquake Research Institute, Associate Professor, 地震研究所, 助教授 (00183385)
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| Co-Investigator(Kenkyū-buntansha) |
HIRATA Naoshi The Univ. of Tokyo, Earthquake Research Institute, Professor, 地震研究所, 教授 (90156670)
IWASAKI Takaya The Univ. of Tokyo, Earthquake Research Institute, Professor, 地震研究所, 教授 (70151719)
UMINO Norihito Tohoku Univ., Graduate school of Science, Associate Professor, 大学院・理学研究科, 助教授 (30004477)
YOSHIDA Takeyoshi Tohoku Univ., Graduate school of Science, Professor, 大学院・理学研究科, 教授 (80004505)
IKEDA Yasutaka The Univ. of Tokyo, Graduate school of Science, Associate Professor, 大学院・理学系研究科, 助教授 (70134442)
伊藤 谷生 千葉大学, 理学部, 教授 (50111448)
今泉 俊文 山梨大学, 教育人間科学部, 教授 (50117694)
長谷川 昭 東北大学, 大学院・理学研究科, 教授 (40004460)
大口 健志 秋田大学, 工学資源学部, 教授 (40006664)
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| Project Period (FY) |
2000 – 2001
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| Project Status |
Completed (Fiscal Year 2001)
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| Budget Amount *help |
¥42,050,000 (Direct Cost: ¥41,300,000、Indirect Cost: ¥750,000)
Fiscal Year 2001: ¥3,250,000 (Direct Cost: ¥2,500,000、Indirect Cost: ¥750,000)
Fiscal Year 2000: ¥38,800,000 (Direct Cost: ¥38,800,000)
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| Keywords | deep seismic profiling / crustal structure / basin development / back arc basin / Northern Honshu / rift system / Neogene / Japan / 反射法地震探査 / 島弧地殻 / 背弧拡大 / 反転テクトニクス / 東北日本弧 / 後期新生代 / 活断層 / 秋田仙北地震 / 震源断層 / 由利丘陵 |
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| Research Abstract |
Northern Honshu, Japan, is a classical example of a trench-arc-back arc basin system, and provides exceptional opportunities for better understanding plate subduction. In this research, data from deep seismic profiles, petrology and petroleum geology are used to construct a geologic framework for the late Cenozoic development of the back arc area of central northern Honshu. In particular, the deep seismic reflection profiling using four vibroseis trucks and dynamites was performed across the Dewa hills (Yuri hills). The resultant compiles cross section across the central part of the Northern Honshu (Kamaishi to Honjo), portrays the two Miocene rift systems : the Yamato basin rift system along the eastern part of the sea of Japan and the northern Honshu rift system in the western part of northern Honshu island. The eastern part of the Yamato basin rift system is marked by half grabens bound by west-dipping Miocene normal faults, with the thickness of the crust decreasing toward the west due to early Miocene crustal stretching. The northern Honshu rift system is younger, forming in the middle Miocene, and produced the Akita-Yamagata sedimentary basin by a simple shear type of rifting. Basalts were erupted in conjunction with rifting. This produced a high thermal regime, and a shallow brittle/ductile detachment, formed along the rift axis with associated thinning of the upper crust. Middle Miocene basin development was mainly controlled by normal faulting along the detachment. Based on our balanced geologic cross-section, the total amount of Miocene extension of the northern Honshu rift system is ca. 40 km. Due to subsequent shortening since Pliocene, the low-angle detachment was reactivated as a thrust.
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