近地表土层平均剪切波速与场地基本频率的相关性研究  

Correlation of site average shear-wave velocity and the fundamental frequency

作　　者：陈童 陈龙伟[1,2] 郭婷婷 刘干 CHEN Tong;CHEN Longwei;GUO Tingting;LIU Gan(Key Laboratory of Earthquake Engineering and Engineering Vibration,Institute of Engineering Mechanics,China Earthquake Administration,Harbin 150080,China;Key Laboratory of Earthquake Disaster Mitigation,Ministry of Emergency Management,Harbin 150080,China)

机构地区：[1]中国地震局工程力学研究所地震工程与工程振动重点实验室,黑龙江哈尔滨150080 [2]地震灾害防治应急管理部重点实验室,黑龙江哈尔滨150080

出　　处：《地震工程与工程振动》2022年第3期190-199,共10页Earthquake Engineering and Engineering Dynamics

基　　金：中国地震局工程力学研究所基本科研业务费专项资助项目(2021EEEVL0104)。

摘　　要：近地表土层平均剪切波速和场地基本频率(简称基频f,下同)是场地地震反应定量化模拟的2个重要指标参数,建立二者之间的相关性,可实现不同参数在场地校正地震动场预测中优势互补。通过建立下卧基岩的单覆盖土层的简化场地模型,分析了场地平均剪切波速与场地基频之间的关系。采用日本KiK-net地震台站场地数据分析,在现有模型的基础上给出了场地近地表20 m和30 m岩土层平均剪切波速(V_(S20)和V_(S30))与场地基频的经验模型。结果显示,采用以拐点频率分段的简化数学模型可以较好地模拟V_(S30)-f和V_(S20)-f之间的关系式,通过数据拟合给出了模型参数的建议值。当场地基频小于拐点频率时,场地平均剪切波速等于覆盖土层的剪切波速,但模型预测平均剪切波速值相对于实测数据离散性较大;当场地基频大于拐点频率时,模型预测与实际数据吻合较好。与已发表的模型对比显示,基于不同地区场地数据建立的模型与本文模型预测结果基本一致。研究结果可为量大面广的场地土层条件校正地震动场的评估提供一种可操作的途径。Site average shear-wave velocity and its fundamental frequency(f)are two important parameters to quantify the seismic site response.To establish a relationship between average shear-wave velocity and site fundamental frequency can be beneficial to take the advantages of the two parameters in predicting ground motion which is corrected by local soil conditions.Based on a simplified site model consisting of a single soil layer sitting on bedrock,the correlation of average shear-wave velocity and site fundamental frequency is analyzed refereeing to a model proposed by others.The site soil profile data at the seismic stations in the Kik-net seismic array,Japan,are adopted to forge the relationships of the average shear-wave velocity of the upper 20 m and 30 m soil layers,i.e.,V_(S20) and V_(S30),with f.The analytical results indicate that the relationships of V_(S20) and V_(S30) with respect to f can be modeled by a simple equation consisting of two segments which are separated by a corner frequency.The model coefficients are obtained by regressing on the site data.When the site fundamental frequency is less than the corner frequency,the model predicts a constant average shear-wave velocity value which is equal to the shear-wave velocity of the soil layer.However,the variability of the model prediction,comparing to the site data,stays large,indicating that the model predictions are much uncertain.When the site fundamental frequency is larger than the corner frequency,the model predictions keep well consistency with the site data.Comparison is made between the model with those proposed by others,that the predictions by different models keep a consistent tendency even though different site data from various regions are used to establish the models.The work presented herein offer a way to correct groundmotion prediction by site conditions in a large scale.

关 键 词：平均剪切波速 场地基本频率 相关性 简化模型 

分 类 号：P315.9[天文地球—地震学]