深厚软土场地基岩地震动反演——以天津波为例

Inversion of bedrock ground motion of thick and soft soils with Tianjin earthquake wave as the example

根据天津波地表加速度记录和相应实测场地钻孔资料,采用等效线性化方法模拟土体非线性,进行了深厚软土场地基岩地震动反演,研究了频率截断对深厚软土场地基岩地震动反演的影响,为天津波地表加速度记录提供了相应的基岩地震动输入。研究表明:不同截断频率情况下,反演得到的基岩地震动峰值和反应谱曲线形状均相差悬殊,但反演后再正演所得到的地面运动与原地表记录相比,加速度时程曲线形状和峰值大小、反应谱曲线形状和峰值大小均非常接近;可根据工程需要对地表加速度记录进行不同频率的截断,反演得到所需强度的基岩地震动。

Based on the surface ground motion(acceleration time-history)of Tianjin earthquake and the corresponding measured site profiles,the inversion of bedrock ground motion of thick and soft soil site is carried out,using the equivalent linearization method to simulate the soft soil nonlinearity.This paper provids the bedrock ground motion of Tianjin earthquake.The influence of cut-off frequency on bedrock ground motion inversion in thick and soft soils is discussed.It is shown that,both the peaks and the response spectral shapes of the bedrock ground motion obtained by the inversion are significantly different for different cut-off frequencies.However,if we input the inversed earthquake motion at the bedrock to make forward response calculation,the shape and peak of the acceleration time-history and the response spectrum the surface ground motion are all in good agreement with the Tianjin earthquake ground motion.The bedrock ground motion with desired amplitude can be inversed by frequency cut-off of ground motion according to engineering demand.