局部场地地震动高频衰减系数估计模型

An estimation model of high frequency attenuation coefficient of ground motion for local site

采用随机有限断层法进行地震动模拟时,选用合理的参数描述特定局部场地近地表高频衰减特征,对评价地震动模拟结果的正确与否具有重要的实践意义.在工程场址地震动参数预测中,如何快速确定参数的取值,是实际应用中亟需解决的问题.首先对场地高频衰减系数κ_(0)与平均剪切波速v_(S30)的相关性进行了分析;然后,基于国内外学者计算得到的546个κ_(0)系数,采用一定时窗内的κ_(0)均方根值,讨论其随平均剪切波速v_(S30)增加的变化趋势.结果表明,虽然κ_(0)具有明显的区域差异性,但其均方根值随着v_(S30)的增大呈现出逐渐减小的趋势.为了得到合理的κ0估计模型,分别采用线性函数、多项式函数、对数线性函数和双对数线性函数对κ_(0)均方根值与v_(S30)的关系进行初步拟合,结果表明,对数线性函数能够较好地描述κ_(0)与v_(S30)之间的关系.最后,基于筛选得到的477个数据,采用最小二乘法对模型参数进行拟合,建立了适合工程应用的κ_(0)-v_(S30)模型.对模型适用性的分析表明,本研究所构建的κ_(0)估计模型能够合理估计地震动的高频衰减影响.

When using the stochastic finite fault method for ground motion simulation,how to select reasonable parameters to describe the near-surface high-frequency attenuation characteristics of a specific local site has important practical significance for evaluating the correctness of ground motion simulation results.In the prediction of ground motion parameters of engineering sites,how to quickly determine the value of parameters is an urgent problem to be solved in practical applications.Firstly,we analyzed the correlation between the high-frequency attenuation coefficient κ_(0) of the site and the average shear wave velocity v_(S30).Then,based on the 546 κ_(0) coefficients calculated by domestic and foreign scholars,the root mean square value of κ_(0) in a certain time window was used to discuss its variation trend with the increase of the average shear wave velocity v_(S30).The results showed that although κ_(0) had obvious regional differences,its root mean square value showed a decreasing trend with the increase of v_(S30).In order to obtain a reasonable κ_(0) estimation model,the linear function,polynomial function,logarithmic linear function and log-log linear function were used to preliminarily fit the relationship between the root mean square value of κ_(0) and v_(S30).The results show that the logarithmic linear function can better describe the relationship between κ_(0) and v_(S30).Finally,based on the 477 data obtained from the screening,the model parameters were fitted by the least square method,and a practical model of κ_0-v_(S30) suitable for engineering applications was obtained.The analysis of the applicability of the model shows that the κ_(0) estimation model constructed in this study can reasonably estimate the high-frequency attenuation of ground motion when predicting engineering site ground motion parameters.