摘要
1999年9月21日台湾集集地震(MW7.6)的近断层强地面运动分布具有2个明显特点:(1)地表水平峰值加速度、峰值速度和位移在断层两侧的分布不对称,上盘效应明显;(2)加速度、速度和位移沿断层方向分布特点不一致。在理论分析和对台湾921集集地震的震源机制和断层面的介质特性研究的基础上,建立起一个简化的有限移动源模型,用有限元方法对设计模型的地面运动进行了数值模拟,模拟结果与921集集地震观测到地面运动分布特点相似,并得到如下结论:在不考虑场地条件等影响因素的情况下,断层面的介质刚度在一定程度上影响近场地震动加速度和速度的大小,地面峰值加速度近似与断层面的介质刚度μ成正比,地面峰值速度近似与断层面的介质刚度的平方根μ成正比。另外,与断层面介质特性有关的断层位错量、断层面的倾角、破裂方式和运动方向等震源机制参数对强地面运动分布特点也有很大的影响。过去的研究通常简单地把近场地面运动分布不均匀性归结为震源破裂过程的复杂性,研究结果进一步表明,震源机制和断层面的介质刚度是造成近场强地面运动分布不均匀性的主要因素,震源的复杂性与震源机制和断层面的介质刚度不均匀分布有关。
The distribution of near-fault strong ground motion during Chi-Chi earthquake （Mw7.6） has two remarkable characters： （1） the distribution of horizontal peak acceleration, peak velocity and displacement along the fault is asymmetric and the effect of hanging-wall is distinct： （2） the distribution of acceleration, velocity and displacement are inconsistent. Based on theoretical analysis of focal mechanism and research on medium rigidity of fault, a model of finite source of Chi-Chi earthquake is established： and then the ground motion of the model is simulated. The distribution characteristics of simulation is similar to that of ground motion monitored by instruments. Without considering the site condition, the rigidity of fault surface affects acceleration and velocity value of near-site strong ground motion to some extent, the peak ground acceleration and velocity are respectively in proportional to media rigidity -μ and √μ Furthermore, the parameters of focal mechanism, such as dislocation, obliquity, rupture mode, have remarkable influence on distribution of strong ground motion. The uneven distribution of strong ground motion near the source is attributed to the complexity of source by former researchers. But our studies result in a farther conclusion, that the mechanism and rigidity of fault surface are the main factors resulting in uneven distribution of strong ground motion near the source, and the complexity of source has relationship with the mechanism and rigidity of fault surface .
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2005年第17期3101-3106,共6页
Chinese Journal of Rock Mechanics and Engineering
基金
国家重点基础研究发展规划(973)项目(2002CB412706)
关键词
地震工程
震源机制
刚度
地面运动
seismic engineering
focal mechanism
rigidity
ground motion
