土層生成速度に基づいた表層崩壊発生周期の推定 一新第三紀堆積岩を基盤とする宮城県富谷丘陵の事

We conduct an estimation of the soil thickness recovery time after the occurrence of shallow landslides, and elucidate landsliding recurrence period in the area underlain chiefly by the Neogene sedimentary rocks, the Tbmiya Hills, north of the Sendai Cit Northeast Japan. On the basis of soil genesis in the landslides occurring in 1986 and 1947-1961, and a power series regression by the least absolute value estimation, the recovery time is inferred to be approximately 100 to 250 years. While, from the rainfall records of the 4 meteorological stations in the vicinity of the investigated area, a wide range of values, from around 100 years to more than 1,000 years, can be calculated for the return period of the maximum 24-hour rainfall of the 1986 event, which triggered about 2,000 landslides or more. The occurrence of heavy rainfall, however, is essentially dominated by stochastic and random processes; thus consequently the recollapse at the same locality on slopes, is more strongly dependent on the soil thickness recovery which can generally be regarded as a time-series phenomenon. It is, therefore, appropriate to understand the recurrence period of shallow landslides based mainly on the recovery time. [ABSTRACT FROM AUTHOR]