| 講演要旨(和文) | | 原子力サイトにおいて実施した高密度地震観測データを用いて，地震増幅特性の不確実性を検討した．観測網のうちの1地点を基準点とし，他の観測点とのスペクトル比を求めた．得られたスペクトル比は一定ではなく，地震毎にバラツク．このバラツキは地盤が完全な平行成層構造ではないことを意味し，バラツキの程度は地震基盤より上部地盤における地震増幅特性の不確実性を反映している．そこで，バラツキの標準偏差（SD）に着目し，その特性を調べた結果，SDは周波数とともに増大し，概ね周波数の対数に比例する特性を示す．また，SDの平均値は，基準点からの距離とともに大きくなる傾向が認められる．したがって，構造物への入力地震動の不確実性を考える場合，上記の特性に留意することが必要である． |
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| | 講演要旨(英文) | | Uncertainty of seismic amplification characteristics was examined. using high-density seismic observation data conducted at the nuclear sites Using one point in the observation network as a reference point, the spectral ratio with other points was obtained. The obtained spectral ratio is not constant and varies from earthquake to earthquake. This variation means that the ground is not completely parallel stratified, and the degree of variation reflects the uncertainty of the seismic amplification characteristics in the upper ground than the seismic basement. As a result of examining the standard deviation (SD) of the variation and investigating its characteristics, SD increases with frequency and shows a characteristic approximately proportional to the logarithm of frequency. And, the average value of SD tends to increase with the distance from the reference point. Therefore, when considering the uncertainty of the input ground motion to the structure, it is necessary to pay attention to the above characteristics. |
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