The main purpose of the site classification or velocity determination at a target site is to obtain or estimate the horizontal site amplification factor (HSAF) at that site during future earthquakes because HSAF would have significant effects on the strong‐motion characteristics. We have been investigating various kinds of methods to delineate the S‐wave velocity structures and the subsequent HSAF, as precisely as possible. After the advent of the diffuse field concept, we have derived a simple formula based on the equipartitioned energy density observed in the layered half‐space for incident body waves. In this study, based on the diffuse field concept, together with the generalized spectral inversion technique (GIT), we propose a method to directly estimate the HSAF of the S‐wave portion from the horizontal‐to‐vertical spectral ratio of earthquakes (eHVSRs). Because the vertical amplification is included in the denominator of eHVSR, it cannot be viewed as HSAF without correction. We used GIT to determine both the HSAF and the vertical site amplification factor (VSAF) simultaneously from strong‐motion data observed by the networks in Japan and then deduced the log‐averaged vertical amplification correction function (VACF) from VSAFs at a total of 1678 sites in which 10 or more earthquakes have been observed. The VACF without a category has a constant amplitude of about 2 in the frequency range from 1 to 15 Hz. By multiplying eHVSR by VACF, we obtained the simulated HSAF. We verified the effectiveness of this correction method using data from observation sites not used in the aforementioned averaging in the frequency range from 0.12 to 15 Hz.

中文翻译：

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从地震的水平与垂直光谱比（eHVSR）直接估算S波站点放大因子的方法

目标站点的站点分类或速度确定的主要目的是，在未来的地震中获得或估计该站点的水平站点放大因子（HSAF），因为HSAF对强运动特征有重大影响。我们一直在研究各种方法，以尽可能精确地描绘S波速度结构和随后的HSAF。在扩散场概念出现之后，我们根据在分层半空间中观察到的入射体波的等分能量密度得出了一个简单公式。在这项研究中，基于扩散场概念以及广义光谱反演技术（GIT），我们提出了一种根据地震的水平与垂直频谱比（eHVSRs）直接估算S波部分的HSAF的方法。因为垂直放大包含在eHVSR的分母中，所以如果不进行校正就不能将其视为HSAF。我们使用GIT从日本网络观测到的强运动数据中同时确定HSAF和垂直位点放大因子（VSAF），然后从VSAF推算出对数平均的垂直位点放大校正函数（VACF），总计1678观测到10次以上地震的地点。无类别的VACF在1至15 Hz的频率范围内具有约2的恒定幅度。通过将eHVSR乘以VACF，我们得到了模拟的HSAF。