| 講演要旨(和文) | | 東北地方太平洋沖地震では、日本各地で広い周期帯域の地震動が観測され、関東平野南西端の足柄平野においても周期数秒の地震動が卓越した。とくに，同平野の西部から中央部において周期２~３秒の地震動が極めて大きかった。本研究では，足柄平野西端部において、免震住宅の大きな応答変位が報告された約2km x 2kmの範囲で小規模なアレイ微動観測を行い，表層地盤のＳ波速度構造を明らかにした。得られた地盤モデルにより求められた表層地盤のサイト増幅特性はローカルな地域特性を示し、免震住宅の大きな応答変位が観測された地点では、周期2秒が大きく卓越していることが分かった。 |
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| | 講演要旨(英文) | | Broadband earthquake ground motions were observed in the entire Japan, during the 2011 off the Pacific coast of Tohoku earthquake. In the Ashigara Valley, which is located in the south-west of Kanto Basin, the earthquake ground motions for periods of several seconds were dominated. Especially, the ground motions for a period of 2 to 3 seconds were extremely large in the western edge of Ashigara Valley. In this study, we estimated shallow S-wave velocity structures by array microtremor observations for the small area of 2km x 2km, in which the large displacement response for the base-isolated houses was observed during the main shock. The site amplification factors obtained using the estimated shallow S-wave velocity structures has clearly locality in this area. In the site which large displacement responses for the base-isolated houses were observed, the site amplification factor for a period of 2 seconds were significantly dominated. |
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