2018年台湾花莲M_(w)6.4地震近断层地震动方向性差异  

Ground motion directionality in the 2018 Taiwan Hualien M_(w)6.4 earthquake

作　　者：赵晓芬 温增平[1] 谢俊举[1] 解全才[2] 刘奕君[1] ZHAO Xiaofen;WEN Zengping;XIE Junju;XIE Quancai;LIU Yijun(Institute of Geophysics,China Earthquake Administration,Beijing 100081,China;Institute of Engineering Mechanics,China Earthquake Administration,Harbin 150080,China)

机构地区：[1]中国地震局地球物理研究所,北京100081 [2]中国地震局工程力学研究所,哈尔滨150080

出　　处：《振动与冲击》2021年第10期235-243,共9页Journal of Vibration and Shock

基　　金：国家重点研发项目(2017YFC1500405,2018YFC1504602-04);国家自然基金项目(51639006,51738001)。

摘　　要：定量研究了2018台湾花莲地震近断层地震动方向性特性,及其与震源破裂机制、断层距离和空间方位的关系,探讨了NGA-West2方向性模型对本次地震方向性的适用性,并给出工程建设中需考虑地震动方向性差异的断层距范围。研究结果表明:花莲地震近断层地震动随观测方向变化表现出显著的差异,最大加速度反应可以达到最小反应的6.4倍;地震动的方向性差异随周期的增大而增大,特别是在T>1.0 s的长周期段更为显著。不同方向上的强度最大值与中值之比的统计均值与NGA-West2方向性模型预测值较吻合;断层距30 km以内地震动具有明显方向性,在断层距5 km范围内的米伦断层附近地震动卓越方向最靠近垂直断层方向;在周期T=0.2 s,0.5 s,1.0 s的较短周期段,地震动卓越方向所在方向较为随机;在周期T=3.0 s,5.0 s,7.5 s的较长周期段,地震动的卓越方向与断层的相对运动方向高度吻合。建议在断层距约30 km范围的近断层区域内,工程建设中需考虑地震动方向性差异的影响,特别是在断层距约10 km范围内应确保工程结构的薄弱位置尽量避开地震动卓越方向。The directionality of the near-fault ground motion,and its relationship with the focal mechanism,fault distances and spatial locations in 2018 Hualien earthquake were investigated.The applicability of the NGA-West2 model for ground motion directionality to the Hualien earthquake was considered.And the fault distance range which needs to consider the influence of the ground motion directionality was given.The results show that:The near-fault strong motions show significant variation with orientation.In various directions,the maximum acceleration response can reach 6.4 times the minimum response.The directionality of ground motions increases with the period,especially with the long period of T>1.0 s.The real ratio of the maximum/median of intensity is in conformity with that obtained by the NGA-West2 model for ground motion directionality.The ground motions exhibit strong directionality within about 30 km from the fault,especially within 5 km,the predominant orientation of ground motions is closest to the perpendicular direction of the fault strike.In the shorter period T=0.2 s,0.5 s and 1.0 s,the predominant orientation of ground motions is relatively random.In the longer period T=3.0 s,5.0 s and 7.5 s,the predominant orientation of ground motions is highly consistent with the relative movement direction of the fault.It is suggested that within about 30 km from the fault,the influence of the ground motion directionality should be considered.Especially,within about 10 km from the fault,it should be ensured that the weak position of the engineering structure should avoid the predominant orientation of ground motions as far as possible.

关 键 词：花莲地震 近断层 方向性差异 卓越方向 

分 类 号：P315[天文地球—地震学]