Dataset: seismic amplification maps of Italy based on site-specific microzonation dataset and one-dimensional numerical approach

Prediction of surface ground motion based on advanced approaches is a non-trivial task at large area. In fact, advanced approaches require a detailed geological and geotechnical subsoil model based on geological, physical and mechanical properties retrieved from in situ investigations and laboratory data, and to perform time consuming numerical simulation of the seismic site response. Bearing in mind that there is a lack of available site investigations and laboratory data at large area, simplified methods based on “soft data” are often adopted. On this regard, a methodology to perform seismic site response analyses at national scale is proposed in this paper, based on the following assumptions: 1) homogeneous areas were identified at national scale based both on morpho-geological and lithological properties, in order to classify and analyse site-data archived in the Italian database of seismic microzonation studies; 2) geotechnical subsoil one-dimensional models of the Italian site conditions were defined according to site-data; 3) in accordance with the reference seismic hazard levels, pseudo-acceleration response spectra were selected as input motions for numerical simulations.
About thirty million numerical simulations of seismic site response were performed, and national maps of seismic shaking amplification factors were produced in terms of ratio of response spectra referred to three intervals of period. This estimation of surface ground motion based on the proposed procedure is a supporting tool for large area territorial and emergency planning.

基于先进方法开展大区域地表地震动（surface ground motion）预测是一项颇具挑战性的任务。实际上，先进方法需基于从原位勘察与实验室数据中获取的地质、物理及力学参数，构建精细化的地质与岩土下伏地层模型，并开展耗时漫长的地震场地响应数值模拟。考虑到大区域范围内可用的场地勘察与实验室数据较为稀缺，基于软数据（soft data）的简化分析方法常被采用。
于此背景下，本文提出了一种可在全国尺度开展地震场地响应分析的方法，其基于如下假设：1）结合地貌地质与岩性特征，在全国尺度划分均质区域，以对意大利地震微区划（seismic microzonation）研究数据库中归档的场地数据进行分类与分析；2）依据场地数据，定义适用于意大利场地条件的岩土下伏地层一维模型；3）参照参考地震危险性水准，选取伪加速度反应谱（pseudo-acceleration response spectra）作为数值模拟的输入地震动。
本研究共计开展约3000万次地震场地响应数值模拟，并基于对应三个周期区间的反应谱比值，生成了全国范围的地震动放大系数（seismic shaking amplification factors）分布图。基于该方法得到的地表地震动估算结果，可作为大区域国土规划与应急规划的辅助支撑工具。