考虑震源机制效应的近断层地震动脉冲特征模型

Pulse characteristic model of near-fault ground motion considering focal mechanism

速度脉冲具有复杂的成因和特性,对大跨工程结构影响显著,因此要在地震危险性概率分析及工程抗震设计中合理考虑速度脉冲的影响,关键是对地震动的脉冲特征进行有效估计,可大震近场记录匮乏,在地震动脉冲特征估计中难以考虑震源的影响.为此,本文借助基于运动学震源模型的地震动合成方法,合成不同震源机制参数情况下的近场地震动场,采取Baker的小波方法,识别合成地震动场中的速度脉冲并计算脉冲周期,基于此建立了考虑震源机制影响的脉冲发生概率模型,对比分析了模型的估计结果.在此基础上,进一步讨论了不同震源机制情况下观测点空间位置对脉冲周期的影响,提出了脉冲周期空间影响因子的概念,并建立其数学模型,用于在脉冲周期估计中进一步考虑地震动脉冲特征的空间差异性.

Velocity pulses have complex causes and characteristics,and have a significant impact on long-span engineering structures.Therefore,to accurately consider the impact of velocity pulse in probabilistic seismic hazard analysis and engineering seismic design,the key is to effectively estimate the pulse characteristics of ground motion.However,due to the insufficiency of near-fault field records for of large earthquakes,it is difficult to consider the focal mechanism in the estimation of the pulse characteristics of ground motion.Therefore,a deterministic physics-based method based on kinematic model is used to simulate near-field ground motions in the near field for various focal mechanism scenarios in this paper.The pulse-like ground motions are identified by the Baker's wavelet method,and then the pulse periods are calculated for each scenario.A pulse occurrence probability model considering the influence of focal mechanism is established,and then the estimation results are further analyzed.On this basis,the influence of the spatial location of the site on the pulse period under different focal mechanisms is further studied and the spatial influence factor of the pulse period is proposed,then a mathematical model is established for the spatial influence factor,which can be used to consider the spatial difference in pulse characteristics of ground motion in the estimation of the pulse period.