Simple estimation method of response characteristics in surface layer based on microtremor H/V spectral ratios

从工程角度出发，提出了一种利用微震H/V谱比估计表层地震反应特征的简单方法，并根据地震观测数据验证了该方法的适用性。我们对观测到的微震H/V数据进行了详细的分析，并将其与地面观测到的地震H/V以及地表与海底之间的传递函数进行了比较。从而证实了地脉动的H/V与地面层的水平和垂直响应特性之比近似。对于一种简单的表层地震反应特性的估计方法，根据各种检验的结果，我们判断用地脉动H/V的峰值频率及其幅值的方法是合适的。为了验证简单估计方法的适用性，将基于Kik-Net钻孔数据的理论地震响应与SIMPLE方法的估计结果进行了比较，并将2004年Kii半岛地震期间托诺强震观测网和诺比河谷强震观测点的观测记录的反应特征与SIMPLE估计结果进行了比较。结果表明，地面最大加速度幅值比值平均值约为1.0，标准偏差约为0.4。因此，考虑1.4倍的估计结果，薄层到厚层地基的地震反应在安全范围内是可以预测的，可以说，该方法对地震反应特征的初步估计是有用的。

From the engineering viewpoint, we proposed a simple estimation method of seismic response characteristics of surface layer using the microtremor H/V spectral ratios, and verified its applicability based on the earthquake observation data.1. We performed the analysis of observed microtremor H/V data in detail, and compared this with the earthquake H/V observed at ground surface and the transfer functions between surface and bottom. Consequently, it was confirmed that microtremor H/V approximates to the ratio of horizontal and vertical response characteristics in surface layer.2. As for a simple estimation method of seismic response characteristics in surface layer, we judged that the method using the peak frequency and its amplitude of microtremor H/V was the appropriate, according to the result of various examinations.3. To verify the applicability of a simple estimation method, the theoretical seismic responses based on the borehole data of KiK-net were compared with the estimation results obtained from a simple method, and also, the comparison between the response characteristics based on the observation records at Tono strong motion observation network and the strong motion observation sites in Nobi valley during the 2004 Off Kii Peninsula Earthquake and the simple estimation results were carried out. As a result, the ratios of maximum acceleration amplitude on ground surface were roughly 1.0 in the average and the standard deviations were about 0.4. Therefore, the seismic responses of the ground with from thin to thick layer are predictable in safety side by considering 1.4 times estimation result, and it can be said that the proposed method is useful for estimating the seismic response characteristics in a preliminary stage.