2013年芦山M_S7.0地震震源参数特征及近断层强地面运动初步估计

Source parameters of the 2013 Lushan M_S7.0 earthquake and the characteristics of the near-fault strong ground motion

2013年4月20日在我国四川省雅安市芦山县发生了MS7.0地震,破坏最严重的宝兴、芦山等极震区烈度达到Ⅷ—Ⅸ度.该文针对芦山MS7.0地震震源参数的特征,结合相关经验关系,对本次地震的震源特征进行了初步分析.结果表明,芦山MS7.0地震为断层动态摩擦过程中的应力下调模式.进一步应用Brune圆盘模型对芦山MS7.0地震近场强地面运动的理论值进行估算,并基于加速度和速度的估算结果计算极震区的最大烈度,约为Ⅷ—X度,与实测的极震区最大烈度Ⅸ度较为接近.选取宝兴和芦山为特征计算点,构建动态复合震源模型,对近断层区域内宝兴和芦山两个特征点进行了模拟计算.模拟结果显示,近断层区域强地面运动呈现持续时间短、高频成分多等特征.

A Ms 7.0 earthquake occurred in Lushan County, Sichuan Province of China on 20 April 2013, and the maximum intensity is up to VIII to IX at Baoxing and Lushan Counties, which are located in the meizoseismal area. This study analyzed the dynamic source process with the source mechanism parameters and empirical relationships, estimated the strong ground motion in the near fault field based on the Brune＇s circle model. A dynamical composite source model （DCSM） has been developed to simulate the near-fault strong ground motion with associated fault rupture properties at Baoxing and Lushan, respectively. The results indicate that the frictional undershoot behavior in the dynamic source process of Lushan Ms？. 0 earthquake is actually different from the over- shoot activity of the Wenchuan MsS. 0 earthquake. Moreover, the predictions of broadband synthetic seismogram for Lushan and Baoxing shows that the strong ground motion simulation is characterized by large peak values, shorter duar- tions and more hige-frequency contents, which is affected by higer value of effective stess drop and asperity slip distribution on the fault plane.