近断层区地震动的有限断层数值模型与分析  

Finite fault source model and analysis for ground motion near-fault zone

作　　者：马海英[1] 邱媛 夏烨 赖明辉 MA Hai-ying;QIU Yuan;XIA Ye;LAI Ming-hui(College of Civil Engineering,Tongji University,Shanghai 200092,China;Sichuan Highway Planning,Survey,Design and Research Institute Ltd,Chengdu 610041,Sichuan,China)

机构地区：[1]同济大学土木工程学院,上海200092 [2]四川省公路规划勘察设计研究院有限公司,四川成都610041

出　　处：《长安大学学报（自然科学版）》2024年第4期77-86,共10页Journal of Chang’an University(Natural Science Edition)

基　　金：中央高校基本科研业务费专项资金项目(2023-2-YB-17);国家重点研发计划项目(2018YFC0809606)。

摘　　要：近场地震动含有脉冲成分,对桥梁的作用响应区别于远场地震动,其破坏更大,会导致桥梁出现坍塌等严重事故。为评估断层场地的近场地震效应,并为跨断层斜拉桥Benchmark模型平台提供近场地震动数据,基于琼山地震旧址的地质结构特征,建立有限有限断层数值模型,进行正演模拟,包括构建断层影响区域、确定断层破裂面的平均滑动、以及点震源地震动模拟。并利用数值模拟得到了观测点,比较数值分析结果与相近等级的记录地震动脉冲特性参数。分析了近断层区域的地震动,验证了有限断层震源数值模型的有效性。结果表明:断层破裂面视倾角越小,地面最大峰值加速度P_(GA)、地面的峰值速度与峰值加速度之比P_(GV2A)和Arias强度I_(a)越大,地震动脉冲性越强。垂直断层破裂面方向的地面峰值加速度P_(GAv)、P_(GV2A)在上盘或在传播方向的数值大于下盘,表现出了近断层地震的上盘效应和方向性效应;而平行断层破裂面方向的地面峰值加速度P_(GAp)、I_(a)和两水平方向的Arias强度之比I_(y2x)的分布规律恰好相反,其原因是横向地震动在下盘观测点的断层距更近,下盘上的效应大于上盘。模拟的M_(w)7.5的正断层地震动除P_(GA)与1999年ChiChi地震CHY101(M_(w)7.62的斜滑断层)较为接近外,其余地震动脉冲特性参数和同类型的1980年Irpinia Sturno(M_(w)6.9的正断层)地震有较高的一致性。For ground motion in near-fault zones includes,the impulsive component usually causes larger damage than that in far-fault ground motion,which results in bridge collapse.In order to assess the near-site seismic effect of the fault site and provide data for Benchmark modeling platform of cable-stayed bridges across faults,a numerical model using finite faults based on the geological and structural characteristics of the old earthquake site in Qiongshan was proposed with an orthotropic simulation,which includes fault impact zones construction,the determination of average slip on fault rupture surfaces and point-source ground vibration simulations.The observation points were obtained,and the analysis results with the impulsive characteristic parameters of the recorded ground of the similar grade were compared with the proposed model.And the ground shaking in the near-fault region was analyzed to verify the finite fault seismic model.The results show that the smaller the apparent dip angle of fault rupture plane has,the larger maximum peak ground acceleration P_(GA)、ratio of peak velocity to ground acceleration P_(GV2A) and Arias strength I_(a) are induced,and the stronger the ground motion pulse is generated.The value of peak ground acceleration in the direction of the vertical fault rupture surface P_(GAv) and P_(GV2A) on the hanging wall or along the direction of propagation is larger than those on the footwall,which displays the hanging wall effect and directional effect of near-fault earthquakes,while the distribution law of peak ground acceleration in the direction of a parallel fault rupture surface P_(GAp),I_(a) and ratio of Arias strength in the two horizontal directions I_(y2x) is on the contrary,which is due to that the lateral ground motion is closer to the faults at the observation points of lower disk.P_(GA) is close to CHY101(M_(w)7.62 oblique slip fault)in 1999ChiChi Earthquake.In addition,the characteristic parameters of other ground motion pulse in the simulated ground motion of Mw7.5normal fault

关 键 词：桥梁工程 有限断层数值模型 正演模拟 地震动 脉冲成分 结构参数 

分 类 号：U442.55[建筑科学—桥梁与隧道工程]