基于InSAR同震形变场反演汶川M_w7.9地震断层滑动分布
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摘要
通过综合分析2008年5月12日汶川地震野外地震地质考察的地表破裂带空间分布及分段资料,结合InSAR干涉形变场资料,构建了五段断层几何结构模型,该模型与野外地震地质考察结果在多数分段上基本一致;基于此五段断层模型,运用敏感性迭代拟合算法反演了汶川地震InSAR同震形变场,获得了断层滑动分布及部分震源参数.结果表明,基于余震精定位获得的地震断层倾角模型模拟的同震形变场与InSAR形变场吻合较好,且残差较小;反演的滑动分布主要集中于地下0～20 km,最大滑动量分别位于北川及青川等地区,最大可达到10 m;沿SW-NE走向,断层面的滑动方向主要以右旋兼逆冲形式为主,在汶川及都江堰地区以强烈的逆冲为主兼有一定右旋走滑分量,在北川及映秀地区以逆冲兼右旋运动为主,在平武及青川等地区则逐渐过渡为以右旋运动为主兼有一定的逆冲分量,其中汶川地区的平均滑动角为97°,北川地区的平均滑动角为11 9°,青川地区平均滑动角为138°.反演矩张量为7.7×10~(20)N·m,矩震级达M_w 7.9.
We have established a five-segment fault model based on field investigation and the linear noncoherent characteristics of InSAR wrapped deformation.The five-segment fault model is consistent with the surface rupture trace of field investigation at most of the segments.Then we use this fault model as constraints to simulate the co-seismic deformation of Wenchuan earthquake derived from InSAR technology.Our favored fault model contains five segments with varied dips, based on the seismogenic structure of precise aftershock relocation.The simulated deformation by forward modeling matches very well the InSAR data with a RMS of 0.3～0.35 m. The inverted slip distribution is concentrated in the depth of 0～20 km and the maximum slip is 10m.Among the largest-slip areas Beichuan area has relatively more concentrated slip at shallower depth than other areas.This may be the deep cause why Beichuan area is the most severely destroyed area in this earthquake.The inverted rake distribution shows that there is a transition along the direction of SW-NE.It is mainly reverse and some right-lateral slip at Wenchuan and Beichuan areas, but it is dominantly right-lateral with some thrusting in Qingchuan area, with the mean rake of 97° and 138° respectively.The inverted seismic moment M_O is 7.7×10~(20) N·m, and the moment magnitude M_w is 7.9.
We have established a five-segment fault model based on field investigation and the linear noncoherent characteristics of InSAR wrapped deformation.The five-segment fault model is consistent with the surface rupture trace of field investigation at most of the segments.Then we use this fault model as constraints to simulate the co-seismic deformation of Wenchuan earthquake derived from InSAR technology.Our favored fault model contains five segments with varied dips, based on the seismogenic structure of precise aftershock relocation.The simulated deformation by forward modeling matches very well the InSAR data with a RMS of 0.3～0.35 m. The inverted slip distribution is concentrated in the depth of 0～20 km and the maximum slip is 10m.Among the largest-slip areas Beichuan area has relatively more concentrated slip at shallower depth than other areas.This may be the deep cause why Beichuan area is the most severely destroyed area in this earthquake.The inverted rake distribution shows that there is a transition along the direction of SW-NE.It is mainly reverse and some right-lateral slip at Wenchuan and Beichuan areas, but it is dominantly right-lateral with some thrusting in Qingchuan area, with the mean rake of 97° and 138° respectively.The inverted seismic moment M_O is 7.7×10~(20) N·m, and the moment magnitude M_w is 7.9.
引文
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[3] Steven N Ward, Gianlucar Valensise. Fault parameters and slip distribution of the 1915 Avenzzano, Italy, earthquake derived from geodetic observations. Bulletin of the Seismological Society of America, 1989,79(3) : 690～710
[4] Delouis B, Giardini D, Lundgren P, et al. Joint inversion of InSAR, GPS, teleseismic, and strong-motion data for the spatial and temporal distribution of earthquake slip: application to the 1999 Izmit Mainshock. Bulletin of the Seismological Society of America ,1992,92(1) :278～299
[5] Lasserre G C, Peltzer F, Crampe', et al. Coseismic deformation of the 2001 M_w = 7． 8 Kokoxili earthquake in Tibet, measured by synthetic aperture radar interferometry. J. Geophys. Res., 2005, 110, B12408, doi: 10． 1029/ 2004JB003500
[6] Mahdi Motagh, Rongjiang Wang, Thomas R Walter, et al. Coseismic slip model of the 2007 August Pisco earthquake (Peru) as constrained by Wide Swath radar observations. Geophys. J. Int. , 2008, 174:842～848
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[10] Ji Chen,Gavin Hayes. Preliminary result of the May 12,2008 M_w7．9 eastern Sichuan,China earthquake.http://earthquake.usgs.gov/eqcenter/eqint henews/2008/ us2008 ryan/finite_fault. php
[11] Okada Y. Surface deformation due to shear and tensile fault in a half-space. Bull. Seism. Soc. Am., 1985, 75:1135～1154
[12] Okada Y. Internal deformation due to shear and tensile fault in a half-space. Bull. Seism. Soc. Am., 1992, 82: 1018～1040
[13] Wang R, Motagh M, Walter T R. Inversion of slip distribution from co-seismic deformation data by a sensitivitybased iterative fitting ( SBIF ) method. EGU General Assembly 2008, 2008,10, EGU2008-A-07971
[14] 屈春燕,宋小刚,张桂芳等.汶川M_S8． 0地震InSAR同震形变场特征分析.地震地质,2008,30(4) :1076～1084 Qu C Y, Song X G, Zhang G F, et al. Analysis on the characteristics of InSAR coseismic deformation of the M_S8． 0 Wenchuan earthquake. Seismology and Geology ( in Chinese), 2008, 30(4) :1076～1084
[15] Du Yijun, Atilla Dydin, Paul Segall. Comparison of various inversion techniques as applied to the determination of a geophysical deformation model for the 1983 Borah Peak earthquake. Bulletin of the Seismological Society of America, 1992, 82(4) : 1840～1866
[16] Yukitoshi Fukahata, Tim J Wright. A non-linear geodetic data inversion using ABIC for slip distribution on a fault with an unknown dip angle. Geophys. J. Int. , 2008, 173． :353～ 364
[17] Rowena B Lohman, Mark Simons. Some thoughts on the use of InSAR data to constrain models of surface deformation: Noise structure and data downsampling. Geochem. Geophys. Geosyst. , 2005,6, Q01007, doi: 10． 1029/2004GC000841
[18] 孙建宝,徐锡伟,沈正康等.基于线弹性位错模型及干涉雷达同震形变场反演1997年玛尼M_w7． 5级地震参数一I.均匀滑动反演.地球物理学报,2007,50(4) :1097～1110Sun J B, Xu X W, Shen Z K,et al. Parameter inversion of the 1997 Mani earthquake from INSAR co-seismic deformation field based on linear elastic dislocation model-I. Uniform slip inversion. Chinese. J. Geophys. (in Chinese), 2007 ,50(4) : 1097 ～ 1110
[19] Jonsson S,Zebker H,Segall P,et al. Fault slip distribution of the 1999 M_w7． 1 Hector Mine, California, earthquake, estimated from satellite radar and GPS measurements. Bulletin of the Seismological Society of America, 2002,92 (4) :1377～1389
[20] 陈九辉,刘启元,李顺成等.汶川M_S8． 0地震余震序列重新定位及其地震构造研究.地球物理学报,2009,52(2) :390～397Chen J H, Liu Q Y, Li S C, et al. Seismotectonic study by relocation of the Wenchuan Ms8． 0 earthquake sequence. Chinese J. Geophys. (in Chinese), 2009,52(2) :390～397
[21] 邓起东,陈社发,赵小麟.龙门山及其邻区的构造和地震活动及动力学.地震地质,1994,166(4) :389～403Deng Q D, Chen S F, Zhao X L. Tectonics, seismicity and dynamics of Longmenshan Mountains and its adjacent regions. Seismology and Geology (in Chinese), 1994, 16(4) :389～403
[22] Ken Xiansheng Hao, Hongjun Si, Hiroyuki Fujiwara, et al. Coseismic surface-ruptures and crustal deformations of the 2008 Wenchuan earthquake M_w7． 9, China. Geophys. Res.Lett. , 2009, 36, Ll1303, doi:10． 1029/2009GL037971
[23] Garth J Funning, Barry Parsons, Tim J. Wright. Fault slip in the 1997 Manyi, Tibet earthquake from linear elastic modelling of InSAR displacements. Geophys. J. Int. , 2007,169:988～1008
[24] Kanamori H. The energy release in great earthquakes. J. Geophys. Res. , 1977, 82:2981～2987
[25] 王卫民,赵连锋,李娟等.四川汶川8． 0级地震震源过程.地球物理学报,2008,51(5) :1403～1410Wang W M, Zhao L F, Li J, et al. Rupture process of the M_s8． 0 Wenchuan earthquake of Sichuan, China. Chinese J.Geophys. (in Chinese), 2008,51(5) :1403～1410
[2] Avouac J P, Tapponnier P. Kinematic model of active deformation in central-Asia. Geophysical Research Letters,1993,20:895～898
[3] Steven N Ward, Gianlucar Valensise. Fault parameters and slip distribution of the 1915 Avenzzano, Italy, earthquake derived from geodetic observations. Bulletin of the Seismological Society of America, 1989,79(3) : 690～710
[4] Delouis B, Giardini D, Lundgren P, et al. Joint inversion of InSAR, GPS, teleseismic, and strong-motion data for the spatial and temporal distribution of earthquake slip: application to the 1999 Izmit Mainshock. Bulletin of the Seismological Society of America ,1992,92(1) :278～299
[5] Lasserre G C, Peltzer F, Crampe', et al. Coseismic deformation of the 2001 M_w = 7． 8 Kokoxili earthquake in Tibet, measured by synthetic aperture radar interferometry. J. Geophys. Res., 2005, 110, B12408, doi: 10． 1029/ 2004JB003500
[6] Mahdi Motagh, Rongjiang Wang, Thomas R Walter, et al. Coseismic slip model of the 2007 August Pisco earthquake (Peru) as constrained by Wide Swath radar observations. Geophys. J. Int. , 2008, 174:842～848
[7] 陈运泰,许力生,张勇等.2008年5月12日汶川特大地震震源特性分析报告.中国地震信息网,http://www.csi.ac.cn/sichuan/chenyuntai. pdf. 2008[2008-05-14] Chen Y T, Xu L S, Zhang Y, et al. The report of source characteristics of the May 12, 2008 Wenchuan Earthquake. Earthquake Information Center, China Earthquake Administration. http://www. csi. ac. cn/sichuan/chenyuntai. pdf. 2008[2008-05-14]
[8] 徐锡伟,闻学泽,叶建青等.汶川M_s8． 0地震地表破裂带及其发震构造.地震地质,2008,30(3) :597～629Xu X W, Wen X Z, Ye J Q, et al. The Ms8． 0 Wenchuan earthquake surface ruptures and its seismogenic structure.Seismology and Geology (in Chinese), 2008, 30 (3) : 597 ～629
[9] 何宏林,孙昭民,王世元等.汶川Ms8． 0地震地表破裂带.地震地质,2008,30(2) :359～362 He H L, Sun Z M, WangSY, et al. Rupture of the M_S8． 0 Wenchuan earthquake along Baishanhe river. Seismology and Geology (in Chinese), 2008,30(2) :359～362
[10] Ji Chen,Gavin Hayes. Preliminary result of the May 12,2008 M_w7．9 eastern Sichuan,China earthquake.http://earthquake.usgs.gov/eqcenter/eqint henews/2008/ us2008 ryan/finite_fault. php
[11] Okada Y. Surface deformation due to shear and tensile fault in a half-space. Bull. Seism. Soc. Am., 1985, 75:1135～1154
[12] Okada Y. Internal deformation due to shear and tensile fault in a half-space. Bull. Seism. Soc. Am., 1992, 82: 1018～1040
[13] Wang R, Motagh M, Walter T R. Inversion of slip distribution from co-seismic deformation data by a sensitivitybased iterative fitting ( SBIF ) method. EGU General Assembly 2008, 2008,10, EGU2008-A-07971
[14] 屈春燕,宋小刚,张桂芳等.汶川M_S8． 0地震InSAR同震形变场特征分析.地震地质,2008,30(4) :1076～1084 Qu C Y, Song X G, Zhang G F, et al. Analysis on the characteristics of InSAR coseismic deformation of the M_S8． 0 Wenchuan earthquake. Seismology and Geology ( in Chinese), 2008, 30(4) :1076～1084
[15] Du Yijun, Atilla Dydin, Paul Segall. Comparison of various inversion techniques as applied to the determination of a geophysical deformation model for the 1983 Borah Peak earthquake. Bulletin of the Seismological Society of America, 1992, 82(4) : 1840～1866
[16] Yukitoshi Fukahata, Tim J Wright. A non-linear geodetic data inversion using ABIC for slip distribution on a fault with an unknown dip angle. Geophys. J. Int. , 2008, 173． :353～ 364
[17] Rowena B Lohman, Mark Simons. Some thoughts on the use of InSAR data to constrain models of surface deformation: Noise structure and data downsampling. Geochem. Geophys. Geosyst. , 2005,6, Q01007, doi: 10． 1029/2004GC000841
[18] 孙建宝,徐锡伟,沈正康等.基于线弹性位错模型及干涉雷达同震形变场反演1997年玛尼M_w7． 5级地震参数一I.均匀滑动反演.地球物理学报,2007,50(4) :1097～1110Sun J B, Xu X W, Shen Z K,et al. Parameter inversion of the 1997 Mani earthquake from INSAR co-seismic deformation field based on linear elastic dislocation model-I. Uniform slip inversion. Chinese. J. Geophys. (in Chinese), 2007 ,50(4) : 1097 ～ 1110
[19] Jonsson S,Zebker H,Segall P,et al. Fault slip distribution of the 1999 M_w7． 1 Hector Mine, California, earthquake, estimated from satellite radar and GPS measurements. Bulletin of the Seismological Society of America, 2002,92 (4) :1377～1389
[20] 陈九辉,刘启元,李顺成等.汶川M_S8． 0地震余震序列重新定位及其地震构造研究.地球物理学报,2009,52(2) :390～397Chen J H, Liu Q Y, Li S C, et al. Seismotectonic study by relocation of the Wenchuan Ms8． 0 earthquake sequence. Chinese J. Geophys. (in Chinese), 2009,52(2) :390～397
[21] 邓起东,陈社发,赵小麟.龙门山及其邻区的构造和地震活动及动力学.地震地质,1994,166(4) :389～403Deng Q D, Chen S F, Zhao X L. Tectonics, seismicity and dynamics of Longmenshan Mountains and its adjacent regions. Seismology and Geology (in Chinese), 1994, 16(4) :389～403
[22] Ken Xiansheng Hao, Hongjun Si, Hiroyuki Fujiwara, et al. Coseismic surface-ruptures and crustal deformations of the 2008 Wenchuan earthquake M_w7． 9, China. Geophys. Res.Lett. , 2009, 36, Ll1303, doi:10． 1029/2009GL037971
[23] Garth J Funning, Barry Parsons, Tim J. Wright. Fault slip in the 1997 Manyi, Tibet earthquake from linear elastic modelling of InSAR displacements. Geophys. J. Int. , 2007,169:988～1008
[24] Kanamori H. The energy release in great earthquakes. J. Geophys. Res. , 1977, 82:2981～2987
[25] 王卫民,赵连锋,李娟等.四川汶川8． 0级地震震源过程.地球物理学报,2008,51(5) :1403～1410Wang W M, Zhao L F, Li J, et al. Rupture process of the M_s8． 0 Wenchuan earthquake of Sichuan, China. Chinese J.Geophys. (in Chinese), 2008,51(5) :1403～1410
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