随机有限断层方法的改进和芦山地震动模拟

Strong ground motion simulation of Lushan earthquake with a modified stochastic finite-fault method

随着随机有限断层方法被逐步推广至宽频带地震动的震前预测与震后模拟,该方法存在的2类问题凸显:(1)模拟地震动的频率非平稳特性缺失;(2)高低频地震动的模拟精度不一致。文中探索上述问题的改进措施:(1)引入区域地震波传播群速度模型以生成频率非平稳地震动相位;(2)引入王国新改进震源谱代替Brune震源谱以实现高低频地震动辐射水平的调整。将改进后的随机有限断层方法应用于2014年芦山地震(Mw6.7)的强地震动模拟,模拟结果验证了改进措施的有效性:新引入相位使得模拟记录的频率非平稳特性趋近于真实记录;新引入震源谱模型在一定程度上可实现高低频地震动的一致精度模拟。

With the gradual promotion of the stochastic finite-fault method to the forecasts and hindcast simulation of broadband ground motion,two problems existing in this method are highlighted:(1)Lack of true phase information in simulation records;(2)The simulation accuracy of high and low frequency is inconsistent.Thus,the improvement measures of the method are explored in this paper.An equivalent group velocity model of regional seismic wave propagation is introduced to generate frequency nonstationary phase;Wang’s improved source spectrum is introduced to replace the Brune source spectrum in order to adjust the radiation level of high and low frequency ground motion.Finally,the improved stochastic finite-fault method is applied to simulate the Lushan earthquake(Mw6.7)in 2014.The simulation results verify the effectiveness of the improvement measures:the nonstationary phase is introduced to make the closer prediction time history.The new source spectrum is introduced to ensure the consistent simulation accuracy of high and low frequency ground motion in some degree.