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| | Abstract | | 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. |
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