2019 Fiscal Year Final Research Report
Comprehending InSAR-detected non-tectonic deformation triggered by earthquakes
| Project/Area Number |
17K01234
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Research Field |
Geography
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| Research Institution | Nihon University |
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Principal Investigator |
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| Co-Investigator(Kenkyū-buntansha) |
八木 浩司 山形大学, 地域教育文化学部, 教授 (40292403)
中埜 貴元 国土地理院(地理地殻活動研究センター), その他部局等, 研究官 (60511962)
宇根 寛 国土地理院(地理地殻活動研究センター), その他部局等, 地理地殻活動研究センター長 (20415037)
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| Project Period (FY) |
2017-04-01 – 2020-03-31
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| Keywords | 活断層 / トレンチ / 活断層 / 変位地形 / リモートセンシング / SAR / 干渉SAR / 14C年代 |
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| Outline of Final Research Achievements |
Geological and geomorphological researches around the Matoishi Bokujo I fault, where cracks were yielded by the 2016 Kumamoto earthquake, Japan, gave the following results. By displacement analysis using synthetic aperture radar interferometry (InSAR) of Advanced Land Observing Satellite-2 data, up-down displacement was 10-15 cm along the fault scarp. By trenching survey, upper surface of the Aso-4 (Aso-4 surface) pyroclastic flow deposits that is the key bed was observed ca.3 m and 0.5 m below the ground surface, at the foot and at the middle slope along the north side of the fault, respectively. By ground penetrating radar survey, though Aso-4 surface were not observed 4 m below the ground surface at the lowland along the south side of the fault, they were observed 4-5 m below the ground surface at the upper slope along the north side. These suggest that the elevation difference of the Aso-4 surface was estimated as 13 m and more, caused by the past cumulative faulting displacements.
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| Free Research Field |
地形学 リモートセンシング
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| Academic Significance and Societal Importance of the Research Achievements |
従来，断層変位地形から計測される比高は，地震動を放出する断層運動のみによって生じ，その変位量や地層から得られる年代等，断層の平面的な長さから，地震の発生周期や発生規模が見積もられてきた。しかし，対象とした的石牧場I断層は2016年熊本地震によって受動的に変位が生じた可能性があり，それが約3,300年以降にも生じていたことを示した。このことから，断層変位地形の計測から地震動を放出するような規模の地震の発生周期を見積もる従来の方法に限界があることを指摘した。
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