The application of earthquake recordings to the estimation of an event’s magnitude and the construction of rapid‐response ground‐motion maps requires an adequate classification of the recording stations in terms of their site response. For permanent stations, this information can be obtained from a sufficiently large database of past recordings.In this work, we analyze more than 7300 three‐component recordings collected between 1996 and 2017 by 67 permanent stations in northeastern Italy to assess their site amplification. The signals come from 368 earthquakes with a magnitude range of M 3.2–5.8 and a distance range of 10–300 km. We evaluate the frequency‐dependent amplification function with respect to a reference station with a flat seismic noise horizontal‐to‐vertical spectral ratio. The evaluation relies on the decomposition of the S‐wave amplitude spectra in terms of source, propagation, and site response. We solve the decomposition with a nonparametric, single‐step generalized inversion in the frequency band 0.5–20 Hz. In addition, we compute the amplification factors for peak ground acceleration and velocity with respect to a well‐established ground‐motion prediction equation. The results highlight that only 11 stations show a relatively flat unitary response with respect to the reference site, whereas the frequency‐averaged amplification function at 23 out of 67 stations exhibits a value larger than 2. We classified the sites according to their surface geology and geomorphological scenario and found that amplification affects not only stations installed on the alluvial soil but also several stations installed on what are assumed to be rock sites. Sites in caves and mines exhibit deamplification, whereas the stations with sensors in boreholes exhibit the typical interference pattern. A good correlation between the amplification factors and the frequency‐averaged amplification functions suggests the possibility of predicting time‐domain peak ground‐motion values from amplification functions estimated by generalized inversion.

中文翻译：

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意大利东北部常驻站的站点放大

将地震记录应用于估计事件的震级和构建快速响应地震动图，需要根据站点响应对记录台站进行适当分类。对于永久台站，这些信息可以从足够大的过去记录数据库中获得。在这项工作中，我们分析了 1996 年至 2017 年意大利东北部 67 个永久台站收集的 7300 多个三分量记录，以评估其站点放大。信号来自 368 次地震，震级范围为 M 3.2-5.8，距离范围为 10-300 公里。我们评估了相对于具有平坦地震噪声水平垂直谱比的参考站的频率相关放大函数。评估依赖于 S 波振幅谱在源、传播和站点响应方面的分解。我们在 0.5-20 Hz 频带内使用非参数、单步广义反演求解分解。此外，我们根据完善的地面运动预测方程计算峰值地面加速度和速度的放大系数。结果突出显示，只有 11 个站点相对于参考站点显示出相对平坦的单一响应，而 67 个站点中的 23 个站点的频率平均放大函数表现出大于 2 的值。我们根据地表地质和地貌场景对站点进行分类，发现放大不仅影响安装在冲积土壤上的站点，而且还会影响安装在假定为岩石站点的几个站点。洞穴和矿井中的站点表现出去放大，而在钻孔中带有传感器的站点则表现出典型的干扰模式。放大因子与频率平均放大函数之间的良好相关性表明，可以根据广义反演估计的放大函数预测时域峰值地震动值。