1999年四川绵竹清平5.0级地震序列构造活动特征  

The tectonic active characteristic of the earthquake sequence with magnitude 5.0 in Mianzhu Qingping,Sichuan in 1999

作　　者：赵珠[1] 汪碧澜[1] 龙思胜[1] 陈银[1] 

机构地区：[1]四川省地震局,中国成都610041

出　　处：《地震地磁观测与研究》2001年第6期30-37,共8页Seismological and Geomagnetic Observation and Research

摘　　要：1999年 9月 1 4日四川绵竹清平 5 .0级地震序列是近年发生在青藏高原碰撞带东南边界的龙门山断裂带的规模最大的一次地震活动。本文通过对序列地震震源位置的精确确定 ,对主要的 8次地震震源机制的求解和时间进程中震级频次变化的分析 ,来揭示该震源区地下构造的活动特征。结果表明 :1前震—主震—余震的时间进程完整 ,只是衰减较快 ;2主震位于龙门山中央主断裂弯折的端头 ,与宏观震中十分接近。大部分余震分布在中央主断裂一侧的次级隐伏构造地带 ,与主断裂的北东走向一致。震源深度 3～ 1 5 km;3震源断层面北东取向 ,在指向南东的近水平方向的主压应力作用下 ,断层面的错动以逆冲兼走滑的方式为主 ,间有少量小型的正断层活动 。Qingping,Mianzhu,Sichuan earthquake sequence of M S=5.0 is an earthquake activity on a large scale occurred at Longmenshan fault zone,the east-south edge of Tibetan plateau collision belt in recent years.Through the accurate determination of hypocenter location,the measurement of the 8 main focal mechanism solutions and the analyses of time dependent processes for this earthquake sequence,the tectonic active features of the underground at this hypocenters zone are revealed. The obtained results show:①There is a complete duration of time in Qingping earthquake sequence from the foreshocks to the mian shocks then to the aftershocks,but the level of seismicity reduces much faster.②The microscopic epicenter of main shock is located at the broken end of central Longmenshan faults very near its macroscopic epicenter location.The most aftershocks are distributed along the hidden secondary tectonic zone on one side of the central main faults,and take NE the same direction with the central main fault.The focal depths are ranged from 5 to 15 km.③The fractures of focal fault plane with the NE strike appear out the more overthrust faulting with some strike-slip displacement and a few of normal faulting on a small scale under the near horizontal major principal compressive stress of SE direction,and combine into the slipping migration of underground material towards the SE direction.

关 键 词：龙门山断裂带 绵竹 1999年 四川 地震序列 构造活动 震源断层 

分 类 号：P315.5[天文地球—地震学]