| Project/Area Number |
18H01306
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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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| Review Section |
Basic Section 17040:Solid earth sciences-related
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| Research Institution | Tokyo University of Marine Science and Technology |
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Principal Investigator |
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| Co-Investigator(Kenkyū-buntansha) |
山田 知朗 東京大学, 地震研究所, 助教 (40323654)
八木原 寛 鹿児島大学, 総合科学域総合研究学系, 准教授 (60295235)
山下 裕亮 京都大学, 防災研究所, 助教 (80725052)
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| Project Period (FY) |
2018-04-01 – 2022-03-31
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| Project Status |
Completed (Fiscal Year 2022)
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| Budget Amount *help |
¥17,290,000 (Direct Cost: ¥13,300,000、Indirect Cost: ¥3,990,000)
Fiscal Year 2021: ¥1,690,000 (Direct Cost: ¥1,300,000、Indirect Cost: ¥390,000)
Fiscal Year 2020: ¥1,820,000 (Direct Cost: ¥1,400,000、Indirect Cost: ¥420,000)
Fiscal Year 2019: ¥8,190,000 (Direct Cost: ¥6,300,000、Indirect Cost: ¥1,890,000)
Fiscal Year 2018: ¥5,590,000 (Direct Cost: ¥4,300,000、Indirect Cost: ¥1,290,000)
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| Keywords | 沖縄トラフ / 背弧海盆 / 上部マントル構造 / 地震活動 / 背弧海盆拡大 |
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| Outline of Final Research Achievements |
Five seafloor seismometers were deployed around the Danjyo Basin, located in the northern part of the Okinawa Trough. As a result of hypocenter relocation using the obtained seafloor seismic data and remote island observation data, it was found that the distribution of hypocenters around the Danjyo Basin tends to be linearly aligned and in the form of several clusters. The strike of these clusters is oriented in various directions, indicating that the fault zone forms a complex fault geometry. We also found that the distribution of earthquakes was continuous from the upper crust to the lower crust after the M6.2 earthquake that occurred during the observation period. This seismic activity in the lower crust may be related to the presence of fluid supplied by the uppermost mantle.
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| Academic Significance and Societal Importance of the Research Achievements |
沖縄トラフは現在背弧海盆拡大の最も初期の段階にあると考えられており、その北部延長線上には2016年熊本地震(マグニチュード7.3)が発生した「別府-島原地溝帯」に接続していると考えられている。北部沖縄トラフでは、2015年にM7.1の地震が発生した。この地震の余震分布をみると熊本地震と同じくライン状に震源が分布し、複数の断層帯が複雑に分布していることが分った。熊本地震と同様に日本では珍しい伸長場で発生した大地震の発生様式を考察することは、今後、別府-島原地溝帯で発生の可能性がある地震を考察する上でも重要である。
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