| 講演要旨(和文) | | 2007年中越沖地震の際に震央距離が90kmもある長野県飯綱町で震度6強が観測され,木造家屋に被害が生じた.この研究では,震度6強となり,被害が生じた原因を明らかにするために,地震観測や地盤探査を実施した.その1では,地震被害と現地調査の概要について述べる.さらに,本震による強震記録および同地域で行った地震観測の結果について説明する.被害の多い地域では,周期0.4から1秒の成分が卓越していることがわかった.その2で述べられている地盤探査の結果に基づいて,S波の増幅特性を計算したところ,周期0.6秒に卓越周期が認められ,地震被害の有無は地盤での地震波の増幅効果の影響によって大きく支配されると考えられる. |
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| | 講演要旨(英文) | | Damage of wooden houses was observed in Iizuma in the Nagano prefecture during the 2007 Niigataken Chuetsu-oki earthquake, although the town is about 90km away from the epicenter. The seismic intensity and peak ground acceleration at a strong motion station in the damaged area of the town are 6-upper in the JMA scale and 620 cm/s/s, while those at a site without any damaged wooden houses in the town are 5-upper and 280 cm/s/s. Since the two stations are only 4km apart from each other, it is suggested that site amplification is one of the possible reasons for the differences of the ground motions. We investigated the reasons why the seismic intensity in the town is so high from filed surveys. First, we conducted aftershock observation at 11 sites in the town to understand spatial distribution of earthquake ground motion. Then, geophysical explorations were conducted in the area to known S-wave velocity profiles. Next we investigated effects of shallow soils on earthquake ground motion in the area using the results of the earthquake observation and the geophysical explorations. |
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