2021 Fiscal Year Final Research Report
Post-wildfire Ground Deformation over Permafrost Areas: Detection and Modeling of Spatial-Temporal Changes
| Project/Area Number |
19K03982
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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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| Review Section |
Basic Section 17030:Human geosciences-related
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| Research Institution | Hokkaido University |
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Principal Investigator |
Furuya Masato 北海道大学, 理学研究院, 教授 (60313045)
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| Co-Investigator(Kenkyū-buntansha) |
蟹江 俊仁 北海道大学, 工学研究院, 教授 (10332470)
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| Project Period (FY) |
2019-04-01 – 2022-03-31
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| Keywords | 永久凍土 / 合成開口レーダー干渉法 / 森林火災 / シベリア / 地盤変動 / サーモカルスト / InSAR |
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| Outline of Final Research Achievements |
We detected the post-fire ground displacements by InSAR at the 2014, 2018 and 2019 scars near Batagay, Eastern Siberia, and examined their detailed spatial-temporal changes.The 2014 scar exhibited subsidence signals up to 30 cm at maximum during the 5 post-fire years, accompanying with clear frost heave signals in early winter. The subsiding area does not necessarily correspond to the burn severity. Meanwhile, the 2018 and 2019 scars on the same slope as Batagaika crater revealed rather smaller subsidence amplitude.
We applied the premelting theory of frost-heave to the observed uplift velocity at the 2014 scar. Also, we perform numerical modeling of the derived ground deformation, combining the freezing-thawing process due to thermal conduction along vertical direction with 2-D finite-difference ground-water flow model on the horizontal directions.
We performed onsite measurements of thaw depth, soil moisture and surface temperature in late September 2019, 2020 and 2021.
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| Free Research Field |
測地学，地球物理学
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| Academic Significance and Societal Importance of the Research Achievements |
永久凍土の融解の進行は，広域的かつ緩慢なのか，局所的かつ急激なのか定量的には不明な点が多い．我はシベリアのバタガイ近郊の森林火災跡における地盤変動を合成開口レーダ干渉法を用いて追跡し，火災直後から5年程度の融解過程を明らかにした．また融解深や土壌水分の現地観測データを取得して解釈した．凍土融解による永年的沈降量は，地下氷の量や凍結面の深さで空間的に不均一に変化しており，火災深刻度との関連は薄い．バタガイカクレータと同じ斜面で発生した2018/2019年火災跡の沈降量は2014年火災跡よりも沈降量は少なかったが，防火帯として作られた道で侵食が進行しており今後の監視も必要である．
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