Recurrence History of Slope Failure during the Holocene in Northeastern Japan

濕地 堆積物의 花粉組成과 無機質含量으로 본 東北 日本의 後氷期 四面崩壞 履歷

The stable-unstable curve graph (S-U curve) and the ignition los curve graph (IL curve) for pollen composition and inorganic material content in three areas (namely, Kawadoi Basin, Moniwa-Takada moor, and Nenoshiroishi moor) were prepared to reconstruct the recurrence history of slope failure during the Holocene in Northeastern Japan. Through the S-U curve, a period with a high slope failure frequency of 5,600~4,670yrB.P. was identified in Kawadoi Basin, two of 6,390~5,070yrB.P. and 4,750~3,800yrB.P. in Moniwa-Takada moor, and three of 6,630~6,070yrB.P., 5,890~5,360yrB.P., and 5,000~4,650yrB.P. in Nenoshiroishi moor. Through the IL curve, a period with a high slope failure frequency of 5,600~5,140yrB.P. was identified in Kawadoi Basin, and two of 6,390~6,170yrB.P. and 4,750~2,840yrB.P. in Moniwa-Takada moor. Most of above-mentioned periods were included in the period of slope instability in precedent studies. However, the periods with high slope failure frequency in this study were rather different from those in precedent studies. The times and numbers associated with these periods in each study area also showed discrepancies. Accordingly, to achieve the above-mentioned purpose, more case studies must be performed to improve the reconstruction level of slope failure frequency, which could be explained through the analysis of pollen composition and inorganic material content.

東北 日本의 후빙기 사면붕괴 이력을 복원하기 위하여 3지역(川통盆地, 茂庭, 高田濕原, 根白石濕原)의 습지 퇴적물의 화분조성과 무기질함량을 대상으로 安定-不安定 曲線 그래프(이하 S-U曲線)와 灼熱減量 曲線 그래프(이하 IL曲線)를 작성하였다. 그 결과, S-U曲線에 의하면 사면붕괴 발생빈도가 높은 시기는 川통盆地에서는 약 5,600~4,670yrB.P.의 1회, 茂庭 $\cdot$ 高田濕原에서는 약 6,390~5,070yrB.P.와 약 4,750~3,800yrB.P.의 2회, 根白石濕原에서는 약 6,630~6,070yrB.P., 약 5,890~5,360yrB.P. 및 약 5,000~4,650yrB.P.의 3회가 확인되었다. 그리고 IL曲線에 의하면 사면붕괴 발생빈도가 높은 시기는 川통盆地에서는 약 5,600~5,140yrB.P.의 1회, 茂庭 $\cdot$ 高田濕原에서는 약 6,390~6,170yrB.P.와 약 4,750~2,840yrB.P.의 2회가 확인되었다. 이와같은 분석결과는 선행연구에서 조사지역의 지형 $\cdot$지질단면도로부터 추정된 결과와 매우 유사한 경향을 나타내는 것으로 판명되었다.