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Reference soil condition for intensity prediction equations derived from seismological and geophysical data at seismic stations
Journal of Seismology ( IF 1.6 ) Pub Date : 2020-10-21 , DOI: 10.1007/s10950-020-09962-z
Francesco Panzera , Paolo Bergamo , Donat Fäh

In 2011, an amplification map achieved by macroseismic information was developed for Switzerland using the collection of macroseismic intensity observations of past earthquakes. For each village, a ΔIm was first derived, which reflects the difference between observed and expected macroseismic intensities from a region-specific intensity prediction equation. The ΔIm values are then grouped into geological/tectonic classes, which are then presented in the macroseismic amplification map. Both, the intensity prediction equation and the macroseismic amplification map are referenced to the same reference soil condition which so far was only roughly estimated. This reference soil condition is assessed in this contribution using geophysical and seismological data collected by the Swiss Seismological Service. Geophysical data consist of shear-wave velocity profiles measured at the seismic stations and earthquake recordings, used to retrieve empirical amplification functions at the sensor locations. Amplification functions are referenced to a generic rock profile (Swiss reference rock condition) that is well defined, and it is used for the national seismic hazard maps. Macroseismic amplification factors Af, derived from empirical amplification functions, are assigned to each seismic station using ground motion to intensity conversions. We then assess the factors dΔf defined as the difference between Af and ΔIm. The factor dΔf accounts for the difference between the reference soil condition for the intensity prediction equation and the Swiss reference rock. We finally analysed relationships between Af and proxies for shear-wave velocity profiles in terms of average shear-wave velocity over defined depth ranges, such as VS,30, providing an estimate of the reference shear velocity for the intensity prediction equation and macroseismic amplification map. This study allows linking macroseismic intensity observations with experimental geophysical data, highlighting a good correspondence within the uncertainty range of macroseismic observations. However, statistical significance tests point out that the seismic stations are not evenly distributed among the various geological–tectonic classes of the macroseismic amplification map and its revision could be planned merging classes with similar behaviour or by defining a new classification scheme.



中文翻译:

从地震台站的地震和地球物理数据得出的强度预测方程的参考土壤条件

2011年,瑞士通过收集过去地震的大地震烈度观测资料,开发了通过大地震信息获得的放大图。对于每个村庄,首先得出一个ΔIm,该ΔIm反映了特定区域强度预测方程中观测到的和预期的大地震强度之间的差异。该量ΔIm然后将这些值分组为地质/构造类别,然后将其显示在大地震放大图中。强度预测方程和大地震放大图均以相同的参考土壤条件为参考,到目前为止,该条件仅是粗略估算的。使用瑞士地震局收集的地球物理和地震数据评估了这种参考土壤条件。地球物理数据由在地震台和地震记录中测得的横波速度剖面组成,用于检索传感器位置处的经验放大函数。放大功能参考定义明确的一般岩石剖面(瑞士参考岩石条件),并将其用于国家地震灾害图。大地震放大因子使用地面运动到强度的转换,将从经验放大函数得出的Af分配给每个地震台站。然后,我们评估的因素dΔf定义之间的差别房颤量ΔIm。因子dΔf解释了强度预测方程的参考土壤条件与瑞士参考岩石之间的差异。最后,我们根据定义的深度范围(例如V S,30)上的平均剪切波速度,分析了Af与剪切波速度剖面的代理之间的关系。,为强度预测方程和宏观地震放大图提供参考剪切速度的估算值。这项研究可以将宏观地震烈度观测结果与实验地球物理数据联系起来,突出了在宏观地震观测不确定度范围内的良好对应关系。但是,统计显着性测试指出,地震台站在宏震放大图的各种地质​​构造类别中分布不均,可以计划合并具有相似行为的类别或通过定义新的分类方案对其进行修订。

更新日期:2020-10-27
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