2020 Fiscal Year Final Research Report
Unraveling cascade rupture history of active faults based on small tectonic-geomorphic and sackung features
| Project/Area Number |
16H03112
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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 | Chuo University (2020)
Chiba University (2016-2019) |
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Principal Investigator |
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| Project Period (FY) |
2016-04-01 – 2021-03-31
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| Keywords | 変動地形 / 活断層 / 山体重力変形 / 連動破壊 / 濃尾地震 / 航空レーザー測量 |
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| Outline of Final Research Achievements |
Targeting at active Nukumi, Neodani, and Kurozu faults that ruptured cascadingly in 1891 and resulted in one of the largest inland earthquakes in the Japanese written history, the M 8.0 Nobi earthquake, we conducted on-fault trench excavations as well as pit excavations and coring at near-fault sackung features to reveal detailed rupture histories of those faults prior to the 1891 event. Our results show that the Kurozu fault ruptured only twice in the last 30,000 to 40,000 years whereas the Nukumi and Neodani faults have a rupture interval of as short as 1000 to 3000 years. In particular, at least the latest three ruptures on those two faults, including the 1891 event, all share timing, suggesting that cascade rupture of the Nukumi and Neodani faults might be a rule rather than an exception.
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| Free Research Field |
変動地形学・古地震学
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| Academic Significance and Societal Importance of the Research Achievements |
活断層が連動破壊することにより，個々の活断層から想定される規模を大きく超える地震が発生する場合がある．とくに我が国のような多数の活断層が分布する地域では，こうした現象を適切に評価することが求められるが，実際に連動破壊した活断層群の過去の活動履歴が詳細に明らかにされた例はなく，その評価方法はいまだ確立されていない．1891年濃尾地震時に連動破壊した各活断層の過去の活動履歴・連動履歴を初めて詳細に明らかにした本研究の成果は，活断層の連動破壊条件やそこから発生する将来の地震の規模を検討・評価するための重要な基礎資料となると考えられる．
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