Strong ground motion simulation ofthe Wenchuan earthquake
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摘要: 基于确定性震源模型的方法主要用于计算低频(11 Hz)地震动常用经验格林函数法或随机方法，对低频地震动模拟不够准确．本文在确定性震源模型方法基础上，尝试采用分解给定的震源模型的方法来模拟宽频带(0.1——10 Hz)强地面运动，即采用分级离散断层面和分解断层面破裂单元上升时间的方法，增加震源时间函数中的高频信号，从而避免了对地震记录丰富程度和准确性的依赖．文中模拟计算了汶川MS8.0地震在8个地震观测台的地震动，将模拟结果和观测记录进行了加速度时程曲线和傅里叶振幅谱的对比分析．对比结果显示，模拟估计的地震动峰值加速度和持续时间与观测记录的数据基本在plusmn;50%的精度范围内相同，傅里叶振幅谱显示模拟结果有得到10 Hz左右的高频成分. 四川盆地中的台站模拟结果高频衰减比观测记录要快，原因是模拟过程没有考虑场地效应.对强地震动模拟还是要综合考虑震源、传播路径和场地的影响．研究结果表明,此改变震源输入的确定性方法可应用于模拟近断层宽频强地面运动．Abstract: Theoretical seismology method based on deterministic source function is mainly used in the low frequency wave simulation, since it is hard to simulate high frequency component precisely. High frequency wave can be simulated with stochastic approach or using empirical greenrsquo;s function, but these technique does not work for low frequency. Based on the deterministic simulation method, we try to simulate the broadband frequency (0.1mdash;10 Hz) strong ground-motion by subdividing the slip distribution across the fault plane. This method is to discretize the fault in second order and decompose the rise time variation to increase the high frequency components in the source function, so as to avoid the dependence on the accuracy and richness of seismic records. We simulated ground motions of Wenchuan earthquake at 8 selected stations located near the fault. The results show an overall agreement on the peak acceleration and duration within plusmn;50% tolerance between the simulated and observed accelerations. The simulated Fourier spectra have the components as high as 10 Hz. The simulated Fourier spectrum at the stations in Sichuan basin attenuate faster than the observed because the method did not consider site effect. The strong ground motion simulation should take all the source, propagation path and site effect into consideration. Result of this study indicates that this deterministic method of changing input source function can be applied to simulation of near fault strong ground motion in broad frequency band.
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期刊类型引用(8)
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