基于场地卓越周期的VS30估计方法研究--以川甘地区强震台站为例

Estimation method of V_(S30) by using site period: a case study of strong motion stations in Sichuan and Gansu Province of China

地表以下30 m深度内的平均剪切波速V_(S30)是广泛用于地震动衰减关系和场地分类的场地条件参数,但是由于一些强震台站的场地钻孔资料不完备,无法获得V_(S30)参数,从而影响和限制了台站获得的强震记录被深入挖掘和广泛应用。以中国四川、甘肃地区强震台站的场地资料和数据为基础,通过分析场地卓越周期T_0与场地V_(S30)的关系,建立两者的经验模型。将本研究方法与其他方法估计结果相比表明:本文估计的V_(S30)在表征场地放大方面具有优势,其与场地放大系数之间表现出更强的相关性,且其对场地放大系数的影响规律更符合场地条件对场地放大影响的物理本质;本文方法估计的V_(S30)可以显著减小中国川甘地区场地放大系数的标准差,特别是在周期0.3 s时,减小幅度可达19%。此外,依据不同地区的场地资料,建立了根据场地周期T_0估计V_(S30)的经验模型,不同地区比较表明,经验模型之间存在明显的区域性差别。结论表明,本研究方法可为缺乏详细场地钻孔资料地区估计V_(S30)参数提供参考。

The time-averaged shear-wave velocity of up to 30 mVS30 is widely used in site classification and as a proxy for site amplification in ground-motion prediction equations( GMPEs). Due to the lack of VS30 of some strong motion stations,the usage of which were severely restricted. In order to develop a relationship between VS30 and the site period T0,the data of T0 and VS30 of stations from Sichuan and Gansu Province in China were used in this study. Through comparison with the other methods,results indicated that,compared with the VS30 values predicted from topographic slope,the VS30 values obtained by the method in this paper shows stronger correlations with the site amplification;the effect of evaluated VS30 on the site amplification reflects the nature of influence by site condition on ground motion. Besides,by the usage of VS30 values predicted in this paper,the standard deviation of site amplification estimated for this region can be reduced significantly. Especially,at period of 0. 3 s the maximum reduction can reach 19%. Finally,based on the site data from different regions,the empirical models of site period T0 andVS30 in different regions are studied,comparison results show obvious difference for different regions. Therefore,this method provides a reference for estimating the VS30 parameters in those places with unknown detailed velocity profiles for strong motion stations.