報告書番号

N10050

タイトル（和文）

河成段丘を用いた内陸部隆起量評価手法の適用性の検討 －経験的指標を重視したアプローチ－

タイトル（英文）

Study on applicability of method for uplift evaluation by fluvial terrace inland area - An approach by emphasizing empirical index -

概要 （図表や脚注は「報告書全文」に掲載しております）

日本全国の段丘に関する文献の調査を行い，これまで分布が確認されていた後期更新世の段丘の海岸部に加え，内陸部についても河成段丘の分布を確認し，隆起量評価の可能性を示した．１/５万分図幅の区画で７割におよぶ広い地域で段丘の分布が確認され，少なくとも過去10万年程度の隆起量評価が可能な見通しを得た．また，全国の50地域の模式的地域において，地形面の開析程度，段丘堆積物，被覆層の風化程度，テフラ層序など対比・編年にかかわる情報を統一的な視点で総合的に判断することにより，河成段丘のMIS6の段丘までは対比可能な見通しを得た．段丘面の開析度，段丘礫の風化度，被覆層の赤色化は，日本全国の広い範囲で適用性がある対比指標であることが確認できた．段丘面の開析度には，年代指標としての地域差は認められないが，段丘礫の風化度，被覆層の赤色土は，南西日本ほどより若い段丘に出現する傾向がある．以上の成果をもとに，文献調査ならびに概要調査での段丘対比・編年の実施に向けて，これら指標を積極的に取り入れた具体的な調査の留意点ならびに手順を提案した．

概要 （英文）

Uplift estimation during late Quaternary is required for site selection of geological disposal facility of high level radioactive waste. Marine and fluvial terraces are key indicators for uplift estimation, but the existence of fluvial terraces was not recognized well inland area across Japan. We carried out the literature survey on terrace in Japan in order to investigate the distribution of fluvial terraces in addition to late Pleistocene marine terraces which have been recognized on the coastal area, and confirmed possibility of uplift characterization inland areas. Terrace distribution was confirmed in 70 % widespread area of 1/50,000 topographic map distribution, and we can obtain the out look for the possibility of uplift estimation in at least the past 100,000 years. We can also obtain the out look for the possibility of correlation of MIS6 and younger terraces by means of comprehensive consideration of the information related to chronology and correlation of terraces, which are grades of terrace surface dissection, terrace gravels and covering layers weathering, in 50 regions of typical area across Japan. We confirmed that terrace surface dissection, weathering of terrace gravels and covering layers are good indexes for terrace correlation which can be adopted in wide area across Japan. Terrace surface dissection has no regional differences as an indicator of age in wide area of Japan. On the other hand, weathered terrace gravel and red soil in covering layer of terrace tend to appear on younger terraces in the southwest Japan than the northeast. Based on the above results, we proposed a specific considerations and procedure in a comprehensive terrace correlation and chronology for the Literature and the Preliminary investigation of site estimation for HLW.

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