本論文は,実際の堆積盆地を念頭に置いて,その地震動特性の基本的な性質を調べるために, 2次元AL法による解析的検討を行ったものである.まず,盆地の形状,沖積層と基盤層の物性のコソトラスト,沖積層の減衰性および入射角などが堆積盆地の地震動特性にどのような影響を与えるのかについて調べるために,系統だったパラメトリック・スタディを行っている.次に,比較的薄い堆積盆地においては,直達波の到着後に傾斜境界で生成される表面波が伝播することに着目し,この表面波の性質について検討している.最後に,東京都区部に見られる典型的な沖積谷を対象として,地盤の不整形性が地震動にどの程度影響を与えるかについて考察を行っている.
In the last two decades, many works have been done for studying the effect of surface or subsurface irregularities on ground motion so as to explain very localized and strong variations in large earthquakes damage distributions. Many papers are concerned with the seismic behavior of sediment-filled valleys. But many authors calculated the responses of analytical models with shape ratio (depth to width) larger than that of an actual sediment-filled valley, e.g. Trifunac, 1971; Wong and Trifunac, 1974; Sanchez-Sesma and Esquivel, 1979; Dravinski, 1980; et al., in which it is larger than 0.2. As for the shape ratio of the actual sediment-filled valleys, for large-scaled valleys, e.g. Mexico basin, Kyoto basin and Odawara basin, it is usually less than 0.1. For small-scaled valleys, e.g. many alluvial valleys between loam-layered hills in the city area of Tokyo Metropolis, it is about, 0.03 on the average and about 0.1 maximum. It is hard to find a valley with shape ratio larger than 0.2, except in an artificial case. Therefore, it is necessary to investigate the seismic responses of shallow sediment-filled valleys with shape ratio smaller than 0.2. In this paper, we analyzed responses of sediment-filled valleys with realistic analytical conditions due to incident plane waves by use of the two-dimensional Aki-Larner method.
雑誌名
東京大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, University of Tokyo
巻
65
号
4
ページ
809 - 850
発行年
1991-03-29
ISSN
00408972
書誌レコードID
AN00162258
フォーマット
application/pdf
日本十進分類法
453
出版者
東京大学地震研究所
出版者別名
Earthquake Research Institute, University of Tokyo
2次元AL法による堆積盆地の地震動解析
ji0654001.pdf
(2.8MB)
