1999年四川绵竹清平5.0级地震序列构造活动特征
|
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 ,统一呈现出地下物质向南东的滑移
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.
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.
引文
郭贵安.1997.Prugger方法在汕头地震遥测台网资料定位中的应用.华南地震,17(6):48～54
国家地震局科技监测司.1989.中国分区地震波走时表的编制.北京:地震出版社,115～120
国家地震局科技监测司.1990.地震学分析预报方法程式指南.北京:地震出版社,16～24
赵珠,张润生.1987.四川地区地壳上地幔速度结构的初步研究.地震学报,9(2):154～166
赵珠,丁志峰,易桂喜,王建格.1994.西藏地震定位.地震学报,9(2):154～166
赵珠,陈农.1996.1992年四川力马地震序列期间激发的孕震结构.中国地震,12(1):64～74
赵珠,范军,郑斯华等.1997.龙门山断裂带地壳速度结构和震源位置的精确确定.地震学报,19(6):615～622
赵珠,龙思胜,汪碧澜.2000.1998年四川泸定3.4级地震序列的活动特征.地震学报,22(6):661～665
曾融生,孙为国.1992.青藏高原及其邻区的地震活动和震源机制以及高原物质东流的讨论.地震学报,14(增刊):534～563
周仕勇,许忠淮.1999.地震序列研究综述.中国地震,15(3):268～277
Cross.S JandKisslingerC,1997.Estimating tectonic stress rate and state with landers aftershock,JGR,102,7603～7612
PerezT J,JaimesM A andGarciacaroE,1997.Microseismicity evidence for subduction of theGaribbeanplate beneath the southAmerican plate in north western venezuda,JG R,102,17875～17882
PruggerA F andGendzwillD J,1998.Microearthquake location:a nonlinear approach thatmakes use ofa simplex stepping procedure,BullSeisSoc,Amer,78(2):799～815
国家地震局科技监测司.1989.中国分区地震波走时表的编制.北京:地震出版社,115～120
国家地震局科技监测司.1990.地震学分析预报方法程式指南.北京:地震出版社,16～24
赵珠,张润生.1987.四川地区地壳上地幔速度结构的初步研究.地震学报,9(2):154～166
赵珠,丁志峰,易桂喜,王建格.1994.西藏地震定位.地震学报,9(2):154～166
赵珠,陈农.1996.1992年四川力马地震序列期间激发的孕震结构.中国地震,12(1):64～74
赵珠,范军,郑斯华等.1997.龙门山断裂带地壳速度结构和震源位置的精确确定.地震学报,19(6):615～622
赵珠,龙思胜,汪碧澜.2000.1998年四川泸定3.4级地震序列的活动特征.地震学报,22(6):661～665
曾融生,孙为国.1992.青藏高原及其邻区的地震活动和震源机制以及高原物质东流的讨论.地震学报,14(增刊):534～563
周仕勇,许忠淮.1999.地震序列研究综述.中国地震,15(3):268～277
Cross.S JandKisslingerC,1997.Estimating tectonic stress rate and state with landers aftershock,JGR,102,7603～7612
PerezT J,JaimesM A andGarciacaroE,1997.Microseismicity evidence for subduction of theGaribbeanplate beneath the southAmerican plate in north western venezuda,JG R,102,17875～17882
PruggerA F andGendzwillD J,1998.Microearthquake location:a nonlinear approach thatmakes use ofa simplex stepping procedure,BullSeisSoc,Amer,78(2):799～815
版权所有：© 2023 中国地质图书馆 中国地质调查局地学文献中心