| 講演要旨(和文) | | 2011年東北地方太平洋沖地震の余震観測が行われた茨城県中部の東茨城台地において，表層地盤による増幅特性を理解するために，微動探査によって表層地盤のS波速度構造を推定した．表層地盤は，深部地盤と異なり，空間変化が大きいことがわかった．東茨城台地の西側では表層地盤は浅いものの，中央で最も深くなることを明らかにした．また，微地形区分により推定されるAVS30に比べて，変動が大きいことがわかった．東茨城台地における表層地盤による地盤増幅は，茨城県鉾田市では高周波で卓越し，台地中央や海岸近くでは低周波で卓越することを明らかにした． |
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| | 講演要旨(英文) | | For the purpose of estimation on the shallow part of S-wave velocity structure in the Higashi-Ibaraki Terrace, where strong ground motion was observed during the 2011 off the Pacific coast of Tohoku Earthquake (Mw.9.0), we conducted microtremor array measurements. The phase velocity exhibits high in the western part, while low velocity in the middle of the Higashi-Ibaraki Terrace. The inversion of phase velocities revealed the S-wave velocity in the area. The depth to the engineering bedrock, which has more than 450 m/s, was deep in the middle of the Terrace. The 30m Average S-wave velocity (AVS30) exhibits large variation in the Terrace. The amplification at IBR013 exhibits high in the high-frequency and that in the middle or close to the coastline exhibits high in the low-frequency in the Higashi-Ibaraki Terrace. |
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