汶川8.0级地震序列重新定位及其发震构造初探
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摘要
采用双差定位方法对汶川8.0级地震及其2,216次余震进行了重新定位,得到2,061次地震的震源位置,定位结果在水平向和垂直向的估算误差大致为1～2km和2～3km。8.0级主震的震中位置大致为北纬31.00°,东经103.38°,震源深度13km左右,发震构造为龙门山中央断裂。余震震中沿走向分布的总长度为330km左右,震源深度优势分布在3～20km,表现出明显的分段活动特征。南段以龙门山中央断裂活动为主,后山断裂和前山断裂也有地震发生,这3条断裂自西向东倾角似乎逐渐变缓,形成叠瓦状的破裂分布。北段龙门山中央断裂、平武-青川断裂等多条断裂参与了发震过程,地震破裂既有逆冲推覆,也有右旋走滑方式。
The MS 8.0 Wenchuan earthquake and its 2216 aftershocks were relocated using the double difference algorithm.The horizontal and vertical errors of the 2061 relocated hypocenters are approximately 1～2km and 2～3km,respectively.The epicenter of main shock is approximately 31.00°N,103.38°E,the focal depth is about 13km and the seismogenic structure is the central fault of Longmenshan Fault zone.The total length of spatial distribution of aftershocks along the strike of the fault is about 330km and the predominance distribution of focal depth is 3～20km,which shows obviously the characteristic of segmented activity.The seismicity of the southern part mainly concentrates on the central fault of Longmenshan Fault zone,and some earthquakes occurred on the range-front and range-back faults;the dip of the three faults seems to become gentler gradually from west to east,forming imbricate ruptures.The central fault and Pingwu-Qingchuan Fault of the Longmenshan Fault zone are involved in the seismogenic process,and the seismic rupture is both of thrust napping and right-lateral strike-slipping.
The MS 8.0 Wenchuan earthquake and its 2216 aftershocks were relocated using the double difference algorithm.The horizontal and vertical errors of the 2061 relocated hypocenters are approximately 1～2km and 2～3km,respectively.The epicenter of main shock is approximately 31.00°N,103.38°E,the focal depth is about 13km and the seismogenic structure is the central fault of Longmenshan Fault zone.The total length of spatial distribution of aftershocks along the strike of the fault is about 330km and the predominance distribution of focal depth is 3～20km,which shows obviously the characteristic of segmented activity.The seismicity of the southern part mainly concentrates on the central fault of Longmenshan Fault zone,and some earthquakes occurred on the range-front and range-back faults;the dip of the three faults seems to become gentler gradually from west to east,forming imbricate ruptures.The central fault and Pingwu-Qingchuan Fault of the Longmenshan Fault zone are involved in the seismogenic process,and the seismic rupture is both of thrust napping and right-lateral strike-slipping.
引文
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周庆,徐锡伟,于贵华,等.2008.汶川8.0级地震地表破裂带宽度调查[J].地震地质,30(3):778—787.ZHOU Qing,XU Xi-wei,YU Gui-hua,et al.2008.Investigation on widths of surface rupture zones of theM8.0Wen-chuan earthquake,Sichuan Province,China[J].Seismology and Geology,30(3):778—787(in Chinese).
朱介寿,曹家敏,刘舜化,等.1984.用人工地震初探川西地区的地壳结构[J].成都地质学院学报,3:111—122.ZHU Jie-shou,CAO Jia-min,LIU Shun-hua,et al.1984.A preliminary investigation on crustal structure of western Si-chuan by explosion seismology[J].Bull of Chengdu Institute of Geology,3:111—122(in Chinese).
Geiger L.1912.Probability method for the determination of earthquake epicenters from arrival time only[J].Bull StLouis Univ:60—71.
Waldhauser F,Ellsworth W.2000.A double-difference earthquake location algorithm:Method and application to thenorthern Hayward Fault[J].California Bull Seism Soc Am,90(6):1353—1368.
陈桂华,李峰,郑荣章,等.2008a.逆冲型断裂同震地表变形定量分析的几个问题:以汶川MS8.0地震为例[J].地震地质,30(3):674—682.CHENGui-hua,LI Feng,ZHENG Rong-zhang,et al.2008a.Several issues in the quantitative analysis of co-seismic sur-face rupture produced by reverse faults:A case study from the2008Wenchuan earthquake[J].Seismology andGeology,30(3):674—682(in Chinese).
陈桂华,徐锡伟,郑荣章,等.2008b.2008年汶川MS8.0地震地表破裂变形定量分析:北川-映秀断裂地表破裂带[J].地震地质,30(3):723—736.CHEN Gui-hua,XUXi-wei,ZHENG Rong-zhang,et al.2008b.Quantitative analysis of the co-seismic surface rupture ofthe2008Wenchuan earthquake,Sichuan,China along the Beichuan-Yingxiu Fault[J].Seismology and Geology,30(3):723—736(in Chinese).
吕坚,倪四道,沈小七,等.2007.九江-瑞昌地震的精确定位及其发震构造初探[J].中国地震,23(2):166—174.L Jian,NI Si-dao,SHENXiao-qi,et al.2007.Discussion on the precise relocation and seismo-tectonics of the Jiujiang-Ruichang earthquake[J].Earthquake Research in China,23(2):166—174(in Chinese).
王椿镛,韩渭宾,吴建平,等.2003.松潘-甘孜造山带地壳速度结构[J].地震学报,25(3):229—241.WANG Chun-yong,HAN Wei-bin,WU Jian-ping,et al.2003.Crustal structure beneath the Songpan-Ganzi orogenicbelt[J].Acta Seismologica Sinica,16(3):237—250.
王椿镛,吴建平,楼海,等.2003.川西藏东地区的地壳P波速度结构[J].中国科学(D辑),33(增刊):181—189.WANG Chun-yong,WU Jian-ping,LOU Hai,et al.2003.P wave crustal velocity structure in western Sichuan and east-ern Tibetan region[J].Science in China(Ser D),33(Suppl):254—265.
徐锡伟,闻学泽,叶建青,等.2008.汶川MS8.0地震地表破裂带及其发震构造[J].地震地质,30(3):597—629.XU Xi-wei,WEN Xue-ze,YE Jian-qing,et al.2008.TheMS8.0Wenchuan earthquake surface ruptures and its seis-mogenic structure[J].Seismology and Geology,30(3):597—629(in Chinese).
张培震,徐锡伟,闻学泽,等.2008.2008年汶川8.0级地震发震断裂的滑动速率、复发周期和构造成因[J].地球物理学报,51(4):1066—1073.ZHANG Pei-zhen,XU Xi-wei,WEN Xun-ze,et al.2008.Slip rate and recurrence interval of the Longmen Shan activefault zone,and tectonic implications for the mechanism of the May12,2008Wenchuan earthquake,Sichuan,China[J].Chinese Journal of Geophysics,51(4):1066—1073(in Chinese).
张天中,武巴特尔,黄媛,等.2007.近台资料对近震相对定位算法的影响[J].地球物理学报,50(4):1123—1130.ZHANG Tian-zhong,WU Bater,HUANG Yuan,et al.2007.Effect of the data recorded at nearby stations on earthquakerelative location[J].Chinese Journal of Geophysics,50(4):1123—1130(in Chinese).
张元生,李清河,刘耀伟,等.2003.地震层析成像软件[J].西北地震学报,25(2):170—174.ZHANG Yuan-sheng,LI Qing-he,LIUYao-wei,et al.2003.The seismic tomography software[J].Northwestern Seis-mological Journal,25(2):170—174(in Chinese).
赵珠,范军,郑斯华,等.1997.龙门山推覆构造带地壳速度结构和震源位置的精确修定[J].地震学报,19(6):615—622.ZHAO Zhu,FAN Jun,ZHENG Si-hua,et al.1997.Precision determination of the crustal structure and hypocentral loca-tions in the Longmenshan thrust nappe belt[J].Acta Seismologica Sinica,19(6):615—622(in Chinese).
周龙泉,刘杰,张晓东.2007.2003年大姚6.2、6.1级地震前三维波速结构的演化[J].地震学报,29(1):20—30.ZHOU Long-quan,LIU Jie,ZHANG Xiao-dong.2007.Evolution of3D velocity structure before DayaoM6.2andM6.1earthquakes in2003[J].Acta Seismologica Sinica,29(1):20—30(in Chinese).
周庆,徐锡伟,于贵华,等.2008.汶川8.0级地震地表破裂带宽度调查[J].地震地质,30(3):778—787.ZHOU Qing,XU Xi-wei,YU Gui-hua,et al.2008.Investigation on widths of surface rupture zones of theM8.0Wen-chuan earthquake,Sichuan Province,China[J].Seismology and Geology,30(3):778—787(in Chinese).
朱介寿,曹家敏,刘舜化,等.1984.用人工地震初探川西地区的地壳结构[J].成都地质学院学报,3:111—122.ZHU Jie-shou,CAO Jia-min,LIU Shun-hua,et al.1984.A preliminary investigation on crustal structure of western Si-chuan by explosion seismology[J].Bull of Chengdu Institute of Geology,3:111—122(in Chinese).
Geiger L.1912.Probability method for the determination of earthquake epicenters from arrival time only[J].Bull StLouis Univ:60—71.
Waldhauser F,Ellsworth W.2000.A double-difference earthquake location algorithm:Method and application to thenorthern Hayward Fault[J].California Bull Seism Soc Am,90(6):1353—1368.
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