| 講演要旨(和文) | | 特定サイトの地震動評価に用いる地盤モデルは，一般に地質調査や物理探査等の結果に基づき1次元モデルで作成されることが多いが，その妥当性検証として地震記録を用いた検討は有効な手法の一つである．本研究では，硬岩サイトにおける水平アレイ地震観測記録を用いて，澤田他（2019）を参考に地震波の到来方向ごとの地震動の平均基準化スペクトルを求めた．その結果，基準化スペクトルは方位に依らず概ね一致し，1次元仮定の妥当性を支持する結果を得た．これにより，地震動の基準化スペクトルを用いた増幅特性の検討は，硬岩サイトにおいても1次元モデルの妥当性検証の手法として有効であることを確認した．また，地震動の基準化スペクトルの標準偏差を記録直前の微動の基準化スペクトルの標準偏差と比較した結果，地震動の基準化スペクトルの標準偏差は，環境ノイズレベルによっても影響されている可能性が示唆された． |
|
|
| | 講演要旨(英文) | | The ground model used for evaluation of seismic motion at specific site is generally created as a one-dimensional model based on the geological surveys and geophysical surveys, but examination using seismic records is one of the effective methods for validating it. In this study, we use seismic records by horizontal array observation at a hard rock site consisting of uniform granite except for the very surface layer, and the mean spectral ratio of seismic motion for each arrival direction of seismic waves was obtained with reference to Sawada et al. (2019). As a result, the spectral ratios are almost the same regardless of the arrival direction, and the results support the validity of the one-dimensional assumption of the ground model. Therefore, it was confirmed that the examination of ground amplification characteristics using the spectral ratio of seismic motions is effective as a method for validating the one-dimensional model even at hard rock sites. In addition, as a result of comparing the standard deviation (SD) of the spectral ratio of seismic motions with SD of microtremors immediately before recording, it suggests that is also affected by the environmental noise level as a possible cause of SD of seismic motions. |
|
|
|
| |
|