GPS测定的四川九寨沟M_W6.6地震同震形变
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摘要
2017年8月8日四川阿坝州九寨沟发生M_W6.6地震,震源机制解显示该地震为左旋走滑型地震。对震中周围的GPS连续站观测资料进行处理,获得高频GPS动态形变和静态同震水平位移。震中100km范围内四川松潘和甘肃武都站观测到1 Hz动态形变。距离震中约69km的松潘站观测的同震水平位移为7.4mm。根据少量的GPS静态同震位移反演的同震破裂模型显示本次地震的最大滑动量为376mm,地震矩为7.25×1018 N·m,等效矩震级为M_W6.6。正演计算的同震三维形变场显示本次地震的最大水平位移可达4~5cm,垂直位移呈四象限分布,最大可达1.5cm,区域内10个流动GPS站可观测到同震形变。
The M_W6.6 earthquake occurred in Jiuzhaigou County,Sichuan Province,on August 8,2017.The focal mechanism solution shows that the earthquake was a left-lateral strike-slip earthquake.In this study,the observation data from GPS continuous stations around the epicenter are processed to obtain a high-rate GPS dynamic deformation and static co-seismic horizontal displacement.Through 1 Hz GPS data measurements,dynamic deformation is only observed at the Songpan station in Sichuan Province and Wudu station in Gansu Province within 100 km of the epicentre.The co-seismic horizontal displacement observed by the Songpan station,the nearest continuous station to the epicenter,is 7.4 mm.The co-seismic rupture model inferred based on a small amount of GPS static co-seismic displacement shows that the maximum slippage of the earthquake is 376 mm,the seismic moment is 7.25×1018 N·m,and the equivalent moment magnitude is M W6.6.The co-seismic three-dimensional deformation field obtained by forward calculation shows that the maximum horizontal displacement of this earthquake can reach 4~5 cm,and the vertical displacement can reach a maximum of 1.5 cm in a four-quadrant distribution.The co-seismic deformation can be observed in 10 mobile GPS stations in the region.
The M_W6.6 earthquake occurred in Jiuzhaigou County,Sichuan Province,on August 8,2017.The focal mechanism solution shows that the earthquake was a left-lateral strike-slip earthquake.In this study,the observation data from GPS continuous stations around the epicenter are processed to obtain a high-rate GPS dynamic deformation and static co-seismic horizontal displacement.Through 1 Hz GPS data measurements,dynamic deformation is only observed at the Songpan station in Sichuan Province and Wudu station in Gansu Province within 100 km of the epicentre.The co-seismic horizontal displacement observed by the Songpan station,the nearest continuous station to the epicenter,is 7.4 mm.The co-seismic rupture model inferred based on a small amount of GPS static co-seismic displacement shows that the maximum slippage of the earthquake is 376 mm,the seismic moment is 7.25×1018 N·m,and the equivalent moment magnitude is M W6.6.The co-seismic three-dimensional deformation field obtained by forward calculation shows that the maximum horizontal displacement of this earthquake can reach 4~5 cm,and the vertical displacement can reach a maximum of 1.5 cm in a four-quadrant distribution.The co-seismic deformation can be observed in 10 mobile GPS stations in the region.
引文
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[2]TAPPONNMR P,MOLNAR P.Active Faulting and Tectonics in China[J].Journal of Geophysical Research,1977,82(20):2905-2930.
[3]闻学泽,杜方,张培震,等.巴颜喀拉块体北和东边界大地震序列的关联性与2008年汶川地震[J].地球物理学报,2011,54(3):706-716.WEN Xueze,DU Fang,ZHANG Peizhen,et al.Correlation of Major Earthquake Sequences on the Northern and Eastern Boundaries of the Bayan Har Block,and Its Relation to the2008 Wenchuan Earthquake[J].Chinese Journal of Geophysics,2011,54(3):706-716.
[4]BURCHFIEL B C,ROYDEN L H,HILST R D V D,et al.A Geological and Geophysical Context for the Wenchuan Earthquake of 12 May 2008,Sichuan,People's Republic of China[J].Gsa Today,2008,18(18):4-11.
[5]JONES L M,HAN W,EGILL H,et al.Focal Mechanisms and Aftershock Locations of the Songpan Earthquakes of August1976in Sichuan,China[J].Journal of Geophysical Research,2012,89(NB9):7697-7708.
[6]张军龙,任金卫,付俊东,等.东昆仑断裂带东部塔藏断裂地震地表破裂特征及其构造意义[J].地震,2012,32(1):1-16.ZHANG Junlong,REN Jinwei,FU Jundong,et al.Earthquake Rupture Features and Tectonic Significance of the Tazang Fault in the Eastern Part of the East Kunlun Fault Zones[J].Earthquake,2012,32(1):1-16.
[7]赵斌,谭凯,黄勇,等.GPS测定的四川芦山MW6.6地震同震形变[J].大地测量与地球动力学,2014,34(4):21-26.ZHAO Bin,TAN Kai,HUANG Yong,et al.Coseismic Deformation of Lushan MW6.6Earthquake Inferred from Continuous GPS[J].Journal of Geodesy and Geodynamics,2014,34(4):21-26.
[8]CHEN G.GPS Kinematic Positioning for the Airborne Laser Altimetry at Long Valley,California[D].Mass Inst of Technol,Cambridge,1998.
[9]殷海涛,肖根如,张磊,等.TRACK高频GPS定位中震时参考站的选取方法[J].大地测量与地球动力学,2012,32(4):15-19.YIN Haitao,XIAO Genru,ZHANG Lei,et al.Study on Method for Selecting Reference Station in High Rate GPS Positioning Using TRACK During Earthquake[J].Journal of Geodesy and Geodynamics,2012,32(4):15-19.
[10]HERRING T A,KING R W,McCLUSKY S C.Introduction to GAMIT/GLOBK[R].Mass Inst of Technol,Cambridge,2012.
[11]BACHMANN S,MESSERSCHMITT L,THALLER D.IVS Contribution to ITRF2014[M].Springer Berlin Heidelberg,2015.
[12]谭凯,王琪,丁开华,等.近场位移数据约束的2013年芦山地震破裂模型及其构造意义[J].地球物理学报,2015,58(9):3169-3182.TAN Kai,WANG Qi,DING Kaihua,et al.Rupture Models of the 2013Lushan Earthquake Constrained by Near Field Displacements and Its Tectonic Implications[J].Chinese J Geophys,2015,58(9):3169-3182.
[13]OKADA Y.Internal Deformation Due to Shear and Tensile Faults in a Half-space[J].Bull Seismol Soc Am,1992,82(2):1018-1040.
[14]赵小麟,邓起东,陈社发.岷山隆起的构造地貌学研究[J].地震地质,1994,16(4):429-439.ZHAO Xiaolin,DENG Qidong,CHEN Shefa.Tectonic Geomorphology of the Minshan Uplift in Western Sichuan,Southwestern China[J].Seismology and Geology,1994,16(4):429-439.
[15]JONES L M,HAN W,EGILL H,et al.Focal Mechanisms and Aftershock Locations of the Songpan Earthquakes of August1976in Sichuan,China[J].Journal of Geophysical Research,1984,89(NB9):7697-7708.
[16]岳汉,张竹琪,陈永顺.相邻左旋走滑和逆冲断层之间的相互作用:1976年松潘震群[J].科学通报,2008,53(13):1582-1588.YUE Han,ZHANG Zhuqi,CHEN Yongshun.Interaction between Adjacent Left-lateral Strike-slip and Thrust Faults:Songpan Group in 1976[J].China Science Bulletin,2008,53(13):1582-1588.