| Project/Area Number |
16300293
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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 |
Geography
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| Research Institution | Chiba University |
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Principal Investigator |
MIYAUCHI Takahiro Chiba University, Department of Earth Science, Faculty of Sciences, Associate Professor, 理学部, 助教授 (00212241)
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| Co-Investigator(Kenkyū-buntansha) |
MAEMOKU Hideaki Hiroshima University, Graduate School of Education, Associate Professor, 教育学研究科, 助教授 (50222287)
KARIYA Yoshihiko Chiba University, Graduate School of Natural Science, Research Associate, 大学院・自然科学研究科, 助手 (70323433)
ITO Tanio Chiba University, Graduate School of Natural Science, Professor, 大学院・自然科学研究科, 教授 (50111448)
SHISHIKURA Masanobu Active Fault Research Center, National Institute of Advanced Industrial Science and Technology, 活断層研究センター, 研究員 (00357188)
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| Project Period (FY) |
2004 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥15,200,000 (Direct Cost: ¥15,200,000)
Fiscal Year 2005: ¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2004: ¥11,700,000 (Direct Cost: ¥11,700,000)
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| Keywords | plate convergence / non-seismic subsidence / coseismic uplift / Sanriku Coast / core-boring / radiocarbon dating / Holocene / unusual large earthquake / 機械ボーリング / 広域テフラ / 巨大地震履歴 / 簡易掘削 |
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| Research Abstract |
We investigated the dynamic combination model of seismotecotonic uplift and non-seismotectonic subsidence, in order to understand tectonic processes originated from the plate convergence between the Pacific Plate and the Eurasia Plate, using Quaternary and geomorphological techniques. The obtained results are as follows.
1. A succession of nine marine terraces is recognized, which were formed at interglacial stages at least after MIS21 (ca.800ka). Average uplift rate is estimated to be 0.2 to 0.4m/ka.
2. At least Holocene marine terrace is recognizable at the height in 3 to 5 meters along the 120km long, northern coast of the Sanriku Coast. The emergence age is probably between 7ka and 5ka.
3. Boring core data of 13 short drilling and 2 long drilling show the tectonic history : successive subsidence in rate of 7-9mm/yr between 8ka and 7ka, a possible episodic uplift producing the emergence of shallow marine topography around 2.9ka, and continuous subsidence with the rate of more than 1mm/yr after 2.9ka.
4. Tidal records in the past 50 years at the five ports indicate that the Sanriku Coast is continuously subsiding. The subsidence rate ranges in 2 to 11mm/yr and tend to increase at the port closer to the Japan Trench.
5. At least two co-seismic uplift events are practically estimated in the late Holocene, which likely occurred at 7-5ka and 3ka. This seismic scenario prevides that the recurrence time is about 3000 years and the uplift exceeds 10 meters.
6. The extreme coseismic event of large uplift along the more than 100km long coast requires the extensive interplate faulting or the branching faulting from the plate boundary for the stress release by plate convergence. Such catastrophic faulting is probably associated with the M8-class earthquakes.
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