青海玉树地震的InSAR数据同震形变场模拟与参数反演分析
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摘要
2010年4月我国青海省玉树藏族自治州的玉树县发生了Ms7.1级地震,这次地震(震中33.2°N 96.6°E,Ms=7.1)是由甘孜-玉树断层的强烈活动引起。甘孜-玉树断裂带大部分分布于青海-西藏高原,北西走向。该断裂带和鲜水河断裂带共同组成了巴颜喀拉地块的南边界,二者在甘孜附近成左阶错列分布。在区域构造背景分析和卫星图像、航片解译的基础上,本文给出了玉树地震地表破裂带的空间展布特征。利用D-InSAR(合成孔径雷达差分干涉测量)技术获得了玉树地震的同震形变场,继而得到了地震引起的LOS向的地表位移和发震断层的大致位置。通过对玉树地震同震形变场的分析得到本次地震的动力学特征为明显的左旋走滑。另以同震形变场和发震断层的初始模型,模拟了本次地震的同震形变场,同时通过边界元反演方法得到了断层的特征参数。反演得出的结论和野外调查的结果基本一致。
An earthquake(33.2°N,96.6°E,Ms=7.1) struck Yushu Zang Autonomous Prefecture,Qinghai Province of China on 14 April 2010,which was triggered by the strong activity of Ganzi-Yushu Fault.And the Ganzi-Yushu Fault which distributes mostly in Qinghai-Tibet Plateau orientates NW direction.Also it is the south boundary of Bayanhar Belt together with Xianshuihe Fault,and they are left step nearby Ganzi area.From regional geological results and aero-photos in combination with detailed field study,the ground ruptures show a series of compressional bumps and tension fissures,therefore we can draw a conclusion that all these characteristics reflect the kinematics properties of left-lateral and strike-slip fault.Then D-InSAR(Differential Synthetic Aperture Radar Interferometry) technique is used to acquire the co-seismic deformation field,it gives the spatial distribution of the ground rupture zone of the earthquake in the one hand,and in the other hand the surface displacement in LOS direction was derived and the location of the source fault was determined.According to the analysis of the co-seismic deformation field,it also shows typical characteristics of left-lateral and strike-slip fault.Geodetic inversions are a useful tool for estimating source parameters of earthquakes.Thereby based on the dislocation of co-seismic and the fault plane model,we got the simulation co-seismic deformation field,and simultaneously the fault's attitude is obtained by the boundary element inversion method.There is evident surface rupture along the main shock's causative in the interferogram,and the co-seismic deformation field is about 75km in length and 55km in width.The seismogenic fault of the main shock strikes about N61°W,dips NE,and inverted fault dipping direction and dip-slip are consistent with field investigation.During the process of simulation,we adopted the different fault models respectively.Through the comparison and analysis of different simulation results,we prefer the segmentation fault model.The maximum dislocation in LOS of the earth surface is 0.57m,the seismic moment is about 2.86×1019Nm,which equals to a M_w=6.9 earthquake.
An earthquake(33.2°N,96.6°E,Ms=7.1) struck Yushu Zang Autonomous Prefecture,Qinghai Province of China on 14 April 2010,which was triggered by the strong activity of Ganzi-Yushu Fault.And the Ganzi-Yushu Fault which distributes mostly in Qinghai-Tibet Plateau orientates NW direction.Also it is the south boundary of Bayanhar Belt together with Xianshuihe Fault,and they are left step nearby Ganzi area.From regional geological results and aero-photos in combination with detailed field study,the ground ruptures show a series of compressional bumps and tension fissures,therefore we can draw a conclusion that all these characteristics reflect the kinematics properties of left-lateral and strike-slip fault.Then D-InSAR(Differential Synthetic Aperture Radar Interferometry) technique is used to acquire the co-seismic deformation field,it gives the spatial distribution of the ground rupture zone of the earthquake in the one hand,and in the other hand the surface displacement in LOS direction was derived and the location of the source fault was determined.According to the analysis of the co-seismic deformation field,it also shows typical characteristics of left-lateral and strike-slip fault.Geodetic inversions are a useful tool for estimating source parameters of earthquakes.Thereby based on the dislocation of co-seismic and the fault plane model,we got the simulation co-seismic deformation field,and simultaneously the fault's attitude is obtained by the boundary element inversion method.There is evident surface rupture along the main shock's causative in the interferogram,and the co-seismic deformation field is about 75km in length and 55km in width.The seismogenic fault of the main shock strikes about N61°W,dips NE,and inverted fault dipping direction and dip-slip are consistent with field investigation.During the process of simulation,we adopted the different fault models respectively.Through the comparison and analysis of different simulation results,we prefer the segmentation fault model.The maximum dislocation in LOS of the earth surface is 0.57m,the seismic moment is about 2.86×1019Nm,which equals to a M_w=6.9 earthquake.
引文
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[13]Thomas A L.Poly3D:A Three-Dimensional,Polygo-nal Element,Displacement Discontinuity Boundary El-ement Computer Program with Applications to Frac-tures,Faults,and Cavities in the Earth s Crust[D].Stanford University,1993.
[14]Kanamori H.The Energy Release in Great Earth-quakes[J].Reviews of Geophysics,1997,82(2):2981-2987.
[15]Zhang Yong,Xu Lisheng,Chen Yuntai.SourceProcess of the 2010 Yushu,Qinghai,Earthquake[J].Science China Earth Sciences,2010.
[16]Zhang L,Wu J C,et al.Determining Fault Slip Dis-tribution of the Chi-Chi Taiwan Earthquake with GPSand InSAR Data Using Triangular Dislocation Ele-ments[J].Journal of Geodynamics,2008,45:163-168.
[17]张景发,郭庆十,龚利霞,等.应用InSAR技术测量矿山沉降与变化分析——以河北武安矿区为例[J].地球信息科学,2008,10(5):651-657.
[2]周荣军,马声浩,等.甘孜-玉树断裂带的晚第四纪活动特征[J].中国地震,1996,12(3):250-260.
[3]闻学泽,黄圣睦,江在雄.甘孜-玉树断裂带的新构造特征与地震危险性估计[J].地震地质,1 9 8 5,7(3):2 3-3 2.
[4]李闽峰,刑成起,蔡长星,等.玉树断裂活动性研究[J].地震地质,1995,17(3):218-224.
[5]周荣军,闻学泽,等.甘孜-玉树断裂带的近代地震与未来地震趋势估计[J].地震地质,1997,19(2):115-124.
[6]彭华,马秀敏,白嘉启,等.甘孜玉树断裂带第四纪活动特征[J].地质力学学报,2006,12(3):295-304.
[7]Farr T,et al.The Shuttle Radar Topography Mission[J].Reviews of Geophysics,2007,45(2):1-33.
[8]Jonsson S,et al.Fault Slip Distribution of the 1999Mw 7.1 Hector Mine,California,Earthquake,Esti-mated from Satellite Radar and GPS Measurements[J].BSSA,2002,92(4):1377-1389.
[9]乔学军,等.当雄Ms6.6地震的InSAR观测及断层位错反演[J].大地测量与地球动力学,2009,29(6).
[10]孙建宝,等.升降轨道ASAR雷达干涉揭示的巴姆地震(Mw6.5)3D同震形变场[J].遥感学报,2006,10(4).
[11]张桂芳,单新建,等.利用D-InSAR技术研究西藏改则地震同震形变场[J].地震地质,2009,31(2).
[12]Maerten F,et al.Inverting for Slip on Three-Dimen-sional Fault Surfaces Using Angular Dislocations[J].BSSA,2005,95(5):1654-1665.
[13]Thomas A L.Poly3D:A Three-Dimensional,Polygo-nal Element,Displacement Discontinuity Boundary El-ement Computer Program with Applications to Frac-tures,Faults,and Cavities in the Earth s Crust[D].Stanford University,1993.
[14]Kanamori H.The Energy Release in Great Earth-quakes[J].Reviews of Geophysics,1997,82(2):2981-2987.
[15]Zhang Yong,Xu Lisheng,Chen Yuntai.SourceProcess of the 2010 Yushu,Qinghai,Earthquake[J].Science China Earth Sciences,2010.
[16]Zhang L,Wu J C,et al.Determining Fault Slip Dis-tribution of the Chi-Chi Taiwan Earthquake with GPSand InSAR Data Using Triangular Dislocation Ele-ments[J].Journal of Geodynamics,2008,45:163-168.
[17]张景发,郭庆十,龚利霞,等.应用InSAR技术测量矿山沉降与变化分析——以河北武安矿区为例[J].地球信息科学,2008,10(5):651-657.
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