2013年四川芦山M_S7.0地震强地面运动模拟

Strong ground motion simulation for the 2013 M_S7.0 Lushan,China,earthquake

运用经验格林函数法模拟2013年4月20日芦山MS7.0地震的近场强地面运动.在拟合过程中,首先参考前人远场反演结果给出的滑动量分布特征和主震波形的包络线特征,确定强震动生成区的大致范围和数量;然后利用Somerville等提出的地震矩与凹凸体面积的经验关系式确定强震动生成区细小划分的初值,继而利用遗传优化算法确定以上二者的最优值及其它震源参数.将数值模拟波形与实际地震观测记录在时间域和频率域分别进行比较,结果显示,在所选取的30个观测台站中,多数台站的数值模拟结果与实际观测结果符合得很好,特别是大于1Hz的高频部分.断层面上有两个强震动生成区,其位置与前人反演的滑动量集中分布区相一致,而且强震动生成区规模比Somerville等获得的标度率估计值要小.

The near source strong ground motions of the 2013 MS 7.0 Lushan, China,earthquake were simulated using empirical Green’s function （EGF ） method.At first,we estimated the amount and location of strong motion gene-ration areas （SMGAs）based on the characteristics of both slip distributions from far-field seismic inversion and the envelopes of recorded acceleration from the main shock,and determined the amount of subfaults on SMGAs referring to the scaling law of asperity area versus seismic moment introduced by Somerville et al .Then,we implemented the genetic algorithm searching for the optimized value of above two and other source parameters.Based on the source models, we synthetized the waveforms for the 30 selected stations near the source region.The comparison of the synthetic waveforms with the observed recordsindicated that they agreed very well with each other,especially for the part ofhigh-frequency larger than 1 Hz.We found that there were two obvious SMGAson the fault,which take the position that the asperities from far-field seismicinversion take.The combined SMGAs we obtained were smaller than those predictedby extension of the scaling law by Somerville et al .