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.

在大面积范围内，基于高级方法的地面运动预测是一项复杂的任务。实际上，高级方法需要基于地质、物理和力学性质，从现场调查和实验室数据中获取的详细地质和岩土工程地基模型，并执行耗时耗力的地震场地响应数值模拟。鉴于在大面积范围内缺乏可用的场地调查和实验室数据，通常采用基于“软数据”的简化方法。针对此问题，本文提出了一种在国家级别进行地震场地响应分析的方法，其假设如下：1）基于形态地质学和岩相学特性，在国家级别确定了均质区域，以便对存储在意大利地震微区划研究数据库中的场地数据进行分类和分析；2）根据场地数据，定义了意大利场地条件的岩土工程地基一维模型；3）根据参考地震灾害水平，选择了伪加速度反应谱作为数值模拟的输入运动。进行了约三千万人次的地震场地响应数值模拟，并依据响应谱相对于三个周期间隔的比率，制作了国家级地震震动放大系数图。基于所提出程序的地面运动估计是大型区域领土和紧急规划的支持工具。