基于随场地深度变化相干函数的基岩地震动合成研究

A Study of Bedrock Ground Motion Simulation Based on a Site Depth-Dependent Coherency Function

在地下结构抗震分析及土-结构相互作用体系地震反应分析中,基岩地震动输入的确定是其中关键技术之一.鉴于等效线性化方法在处理反演竖向地震动等问题上的困难,本文采用作者前期建立的随场地深度变化相干函数模型对基岩地震动时程合成方法进行探索研究.文中基于随场地深度变化的相干函数模型,以地表地震动时程为已知地震动,通过Kriging差值估计法获得满足随场地深度相干要求的非平稳基岩地震动时程.随后,以日本KiK-net数据库中选取的地表和基岩实测地震动记录为对象,分别在时域和频域角度将合成的地震动与实测地震动进行对比分析,验证了本文方法的有效性.结果表明:本文建立的基于随场地深度变化相干函数的基岩地震动合成方法能较好地模拟基岩地震动的时域和频域特征;与实测基岩地震动记录相比较,本文的合成误差主要发生在中高频段.

The determination of bedrock ground motion input is one of the key techniques in the seismic analysis of the underground structures and the soil-structure interaction system. In view of difficulties of the equivalent linearization method in treating the inversion problem of vertical ground motion, here we use the site depth-dependent coherency function model established in our earlier work to investigate the bedrock ground motion histories. In this paper, based on the site depth-dependent coherency function model, the non-stationary bedrock ground motion was obtained using the Kriging difference estimation method with the surface ground motion records as the known condition, which satisfy the above depth-dependent coherency requirement.Subsequently, the calculated bedrock ground motion was compared with the recorded data of surface and bedrock motion selected from KiK-net database, in both time domain and frequency domain, to verify the effectiveness of the proposed method. The results show that the established calculation method for bedrock ground motion based on the site depth-dependent coherency function can well simulate the bedrock motion characteristics in both time and frequency domains. The error of the simulation results mainly occurs in the middle and high frequency bands, compared with the measured records.