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Mw7.5级地震参数-Ⅰ.均匀滑动反演
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摘要
1997年11月8日西藏玛尼Mw7.5级地震是干涉雷达技术应用于地震观测以来的一次重要事件.Peltzer等认为该形变场体现了地壳的非线性弹性形变响应,挤压象限和拉张象限的杨氏模量比值为2.相同的情形并没有在其他地震同震形变场中发现,通常用线弹性理论就能够很好地解释观测数据.考虑到他们所用断层模型的简化程度和纯走滑约束等,本研究认为非线性弹性解释是牵强的.应用广泛使用的Okada线弹性位错模型,采用卫星观测得到的地表断层位置,去除倾滑为零的约束,基于非线性优化反演方法寻求拟合雷达观测的最佳断层几何参数和均匀滑动参数.结果表明,线弹性模型能够满意解释观测数据.断层在朝阳湖以东的段落最深达到16.5km,随着断层向两侧延伸,深度逐渐减小;反演得到的断层倾向和倾滑位移与野外调查一致;断层左旋走滑分量最大达到4.44m,同时倾滑分量在相同段达到了最大值1.1m,该量值不能忽略;反演得到的总地震矩为2.08×1020N.m,相当于矩阵级Mw7.5,与哈佛给出的2.23×1020N.m、Velasco等反演得到的1.8×1020N.m较接近.
The Nov. 8, 1997 Mani (Xizang) Mw7.5 Earthquake is an important event since Synthetic Aperture Radar Interferometry was used for earthquake studies. Peltzer et.al argued that the deformation field indicated the nonlinear elastic response of crust with a ratio of 2 between compressive and tensile elastic moduli. No other similar case appeared in co-seismic deformation field. Generally, linear elastic theory can give satisfactory explanation to the observation. Considering their excessively simplified fault model and the pure strike-slip assumption, we deem that nonlinear elasticity explanation is far-fetched. By using the widely-used Okada linear elastic dislocation model and the fault location on the surface from satellite observations, removing the zero dip-slip constraint, we seek best-fit fault geometry parameters and uniform slip vectors from radar observation based on nonlinear optimization inversion. The result shows that linear elastic model can satisfactorily explain the observation. The maximum depth of the fault reaches 16.5 km at the segment near the east side of Chaoyang Lake. The depth decreases gradually when the fault extending to the east and the west; inverted fault dipping direction and dip-slip are consistent with field investigation; the maximum strike-slip component reaches 4.44 m, and the dip-slip component also reaches its maximum 1.1 m at this segment, which can not be ignored in the inversion; the total seismic moment is 2.08×10 20 N·m from inversion, which equals to a Mw7.5 earthquake. The seismic moment is close to the 2.23×10 20 N·m of Harvard solution and the 1.8×10 20 N·m of Velasco's inversion.
The Nov. 8, 1997 Mani (Xizang) Mw7.5 Earthquake is an important event since Synthetic Aperture Radar Interferometry was used for earthquake studies. Peltzer et.al argued that the deformation field indicated the nonlinear elastic response of crust with a ratio of 2 between compressive and tensile elastic moduli. No other similar case appeared in co-seismic deformation field. Generally, linear elastic theory can give satisfactory explanation to the observation. Considering their excessively simplified fault model and the pure strike-slip assumption, we deem that nonlinear elasticity explanation is far-fetched. By using the widely-used Okada linear elastic dislocation model and the fault location on the surface from satellite observations, removing the zero dip-slip constraint, we seek best-fit fault geometry parameters and uniform slip vectors from radar observation based on nonlinear optimization inversion. The result shows that linear elastic model can satisfactorily explain the observation. The maximum depth of the fault reaches 16.5 km at the segment near the east side of Chaoyang Lake. The depth decreases gradually when the fault extending to the east and the west; inverted fault dipping direction and dip-slip are consistent with field investigation; the maximum strike-slip component reaches 4.44 m, and the dip-slip component also reaches its maximum 1.1 m at this segment, which can not be ignored in the inversion; the total seismic moment is 2.08×10 20 N·m from inversion, which equals to a Mw7.5 earthquake. The seismic moment is close to the 2.23×10 20 N·m of Harvard solution and the 1.8×10 20 N·m of Velasco's inversion.
引文
[1]Massonnet D,Rossi M,Cesar C,et al.The displacementfield of theLanders earthquake mapped by radar interferometry.Nature,1993,364(6433):138～141
[2]Peltzer G,CrampF,King G.et al.Evidence of nonlinear elasticity of the crust fromMw7.6Manyi(Tibet)earthquake.Science,1999,286:273～276
[3]Lasserre C,Peltzer G,CrampF,et al.Coseismic deformation of theMw=7.8Kokoxili earthquake in Tibet measured by synthetic aperture radar interferometry.J.Geophys.Res.,2005,110(B12)(B12408).
[4]孙建宝.干涉雷达的地壳形变应用研究[博士论文].北京:北京师范大学,2005Sun J B.Crustal deformation applicationstudy by SARInterferometry[Ph.D.Thesis](in Chinese).Beijing:Beijing Normal University,2005
[5]Wright TJ,Parsons B,England P,et al.InSARobservations of low slip rates onthe major faults of Western Tibet.Science,2004,305:236～239
[6]Zebker H A,Villasenor J.Decorrelation in interferometric radar echoes.IEEETransactions on Geoscience and Remote Sensing,1992,30(5):950～959
[7]Ferretti A,Prati C,Rocca F,et al.Permanent scatterers in SAR interferometry.IEEETransactions on Geoscience and Remote Sensing,2001,39(1):8～20
[8]Xu X W,Chen W,Ma W,et al.Surface rupture of the Kunlunshan earthquake(Ms8.1),Northern Tibetan Plateau,China.Seismological Research Letters,2002,73(6):884～892
[9]徐锡伟,宋方敏,杨晓平等.中国大陆地表破裂型潜在震源区的地震地质学综合判断.震情研究,2000,44(1):14～26Xu X W,Song F M,Yang X P,et al.Geological estimation of ground rupture earthquakes in seismic potential area of Chinese main land.Earthquake Situation Research(in Chinese),2000,44(1):14～26
[10]沈正康,万永革,甘卫军等.东昆仑活动断裂带大地震之间的黏弹性应力触发研究.地球物理学报,2003,46(6):786～795Shen Z K,Wan YG,Gan WJ,et al.Visco-elastic stresstriggering of large earthquakes alongthe Kunlunfault.Chinese J.Geophys.(in Chinese),2003,46(6):786～795
[11]Tapponnier P,Molnar P.Active faulting andtectonics in China.J.Geophys.Res.,1977,82:2905～2930
[12]Van der Woerd J,Ryerson F,Tapponnier P,et al.Holocene left-slip rate determined by cosmogenic surface dating on the Xidatan segment of the Kunlunfault(Qinghai,China).Geology,1998,26(8):695～698
[13]吴珍汉,吴中海,胡道功等.青藏铁路沿线活动断裂与地质灾害图集.北京:地震出版社,2005Wu Z H,Wu Z H,Hu D G,et al.Picture Collection of Active Faults and Geological Hazards along Qinghai-Xizang Railway.Beijing:Seismological Press,2005
[14]Zhang P,Shen Z-K,Wang M,et al.Continuous deformation of the Tibetan Plateaufromglobal positioningsystemdata.Geology,2004,32(9):809～812
[15]Lu Z,Wright TJ,Wicks C,et al.Deformation of the2002Denali fault earthquakes,mapped by Radarsat-1interferometry.EOS,Transactions,American Geophysical Union,2003,84(425):430～431
[16]Velasco A A,Ammon C J,Beck S,et al.Broadband source modeling of the November8,1997,Tibet(Mw7.5)earthquake and itstectonic implications.J.Geophys.Res.,2000,105(B12):28065～28080
[17]Steck L K,Velasco A A,CogbillL A,et al.Improving regional seismic event locationin China.Pure Appl.Geophys.,2001,158:211～240
[18]许力生,陈运泰.1997年中国西藏玛尼Ms7.9地震的时空破裂过程.地震学报,1999,21(5):449～459Xu LS,Chen YT.Temporal-spatial rupture process of1997Mani,Tibet earthquake.Acta Seismological Sinica(in Chinese),1999,21(5):449～459
[19]Fialko Y,Simons M,AgnewD,et al.The complete(3-D)surface displacement field in the epicentral area of the1999Mw7.1Hecor Mine earthquake,California,from space geodetic observations.Geophys.Res.Lett.,2001,28(16):3063～3066
[20]徐锡伟.中国地震年鉴-藏北玛尼地震科学考察.北京:地震出版社,2000Xu X W.Yearbook of China Earthquake Research-Scientific Investigation of Mani Earthquake in North Tibet.Beijing:Seismological Press,2000
[21]Molnar P,Chen W P.Focal depths and fault plane solutions of earthquakes under the Tibetan plateau.J.Geophys.Res.,1983,88:1180～1196
[22]Shen Z-K,Zeng Y,Wang Y,et al.Post-seismic deformation modeling of the2001Kokoxili earthquake,eastern China.European Geophysical Society,Geophysical Research Abstracts,2003,(5):07840
[23]Le Pichon X,Kreemer C,Chamot-Rooke N.Asymmetry in elastic properties andthe evolution of large continental strike-slipfaults.J.Geophys.Res,2005,110,B03405,doi:10.102912004JB003343
[24]单新建,马瑾,王长林等.利用星载D-INSAR技术获取的地表形变场提取玛尼地震震源断层参数.中国科学(D辑),2002,32(10):837～844Shan XJ,Ma J,Wang CL,et al.Extractionof source parameters of Mani earthquake from D-INSAR deformation field.Science in China(Dseries)(in Chinese),2002,32(10):837～844
[25]Massonnet D,Feigl KL.Radar interferometry and its application to changes inthe earth s surface.Reviews ofGeophysics,1998,36(4):441～500
[26]Klinger Y,Xu X W,Tapponnier P,et al.High-resolution satellite imagery mapping of the surface rupture and slip distribution of the Mw7.8,14November2001Kokoxili earthquake,the Kunlun fault,northern Tibet,China.Bulletin of the Seismological Society of America,2005,95(5):1970～1987
[27]Guo J,Lin A,Maruyama T,et al.Newconstraints on recent large earthquakes along the Xidatan-Dongdatan segment of the Kunlun fault,Western China.Bulletin of the Seismological Society ofAmerica,2006,96(1):48～58
[28]Harris R A.Introduction to special section:Stress triggers,stress shadows,andimplicationsfor seismic hazard.Journal ofGeophysical Research-Solid Earth,1998,103(B10):24347～24358
[29]Fialko Y,Sandwell D,Simons M,et al.Three-dimensional deformation caused by the Bam,Iran,earthquake and the origin of shallowslip deficit.Nature,2005,435:295～299
[30]Farr T G,Kobrick M.Shuttle radar topography mission produces a wealth of data.Eos Trans.AGU,2000,81(48):583～585
[31]Rosen P,Hensley S,Joughin I,et al.Synthetic aperture radar interferometry.Proceedings ofthe IEEE,2000,88(3):333～382
[32]Scharroo R,Visser P.Precise orbit determination and gravity field improvement for the ERSsatellites.Journal ofGeophysical Research,1998,103(C4):8113～8127
[33]Brgmann R,Ayhan E,Fielding E,et al.Deformation duringthe12November1999,Dzce,Turkey Earthquake,from GPS and InSAR data.Bull.Seism.Soc.Am.,2002,92(1):161～171
[34]Chen C W.Statistical-cost network-flow approaches to two-dimensional phase unwrapping for radar interferometry[Ph.D.Thesis].Stanford University,2001
[35]Klinger Y,Michel R,King G,et al.Evidence for an earthquake barrier model fromMwsimilar to7.8Kokoxili(Tibet)earthquake slip-distribution.Earth and Planetary Science Letters,2006,242(3-4):354～364
[36]Okada Y.Surface deformation due to shear and tensile faults in ahalf-space.Bulletin ofthe Seismological Society of America,1985,75(4):1135～1154
[37]Wang R,Martin F,FrankRoth M,et al.Computation of deformation induced by earthquakes in a multi-layered elastic crust-FORTRAN programs EDGRN/EDCMP.Comp.Geosci.,2003,29:195～207
[38]Fialko Y.Probingthe mechanical properties of seismicallyactive crust with space geodesy:Study of the coseismic deformation due to the1992Mw7.3Landers(southern California)earthquake.Journal of Geophysical Research-Solid Earth,2004,109,B03307,doi:10.102912003JB002756
[39]Cervelli P,Murray M H,Segall P,et al.Estimating source parametersfromdeformation data,with an application to the March1997earthquake swarmoff the Izu Peninsula,Japan.J.Geophy.R.,2001,106(B6):11217～11237
[40]Jonsson S,Zebker H,Segall P,et al.Fault slip distribution of the1999Mw7.1Hector Mine,California,earthquake,estimated from satellite radar and GPS measurements.Bulletin ofthe Seismological SocietyofAmerica,2002,92(4):1377～1389
[41]MathWorks T.Optimization Toolbox for Use with MATLAB.The Mathworks Inc.,2006
[42]Hanssen R F.Radar Interferometry:Data Explanation and Error Analysis.Dordrecht,Kluwer Academic Publishers,2001
[43]Wright T J.Realistic Error Modeling for InSAR.ESA Fringe03Meeting,2003
[2]Peltzer G,CrampF,King G.et al.Evidence of nonlinear elasticity of the crust fromMw7.6Manyi(Tibet)earthquake.Science,1999,286:273～276
[3]Lasserre C,Peltzer G,CrampF,et al.Coseismic deformation of theMw=7.8Kokoxili earthquake in Tibet measured by synthetic aperture radar interferometry.J.Geophys.Res.,2005,110(B12)(B12408).
[4]孙建宝.干涉雷达的地壳形变应用研究[博士论文].北京:北京师范大学,2005Sun J B.Crustal deformation applicationstudy by SARInterferometry[Ph.D.Thesis](in Chinese).Beijing:Beijing Normal University,2005
[5]Wright TJ,Parsons B,England P,et al.InSARobservations of low slip rates onthe major faults of Western Tibet.Science,2004,305:236～239
[6]Zebker H A,Villasenor J.Decorrelation in interferometric radar echoes.IEEETransactions on Geoscience and Remote Sensing,1992,30(5):950～959
[7]Ferretti A,Prati C,Rocca F,et al.Permanent scatterers in SAR interferometry.IEEETransactions on Geoscience and Remote Sensing,2001,39(1):8～20
[8]Xu X W,Chen W,Ma W,et al.Surface rupture of the Kunlunshan earthquake(Ms8.1),Northern Tibetan Plateau,China.Seismological Research Letters,2002,73(6):884～892
[9]徐锡伟,宋方敏,杨晓平等.中国大陆地表破裂型潜在震源区的地震地质学综合判断.震情研究,2000,44(1):14～26Xu X W,Song F M,Yang X P,et al.Geological estimation of ground rupture earthquakes in seismic potential area of Chinese main land.Earthquake Situation Research(in Chinese),2000,44(1):14～26
[10]沈正康,万永革,甘卫军等.东昆仑活动断裂带大地震之间的黏弹性应力触发研究.地球物理学报,2003,46(6):786～795Shen Z K,Wan YG,Gan WJ,et al.Visco-elastic stresstriggering of large earthquakes alongthe Kunlunfault.Chinese J.Geophys.(in Chinese),2003,46(6):786～795
[11]Tapponnier P,Molnar P.Active faulting andtectonics in China.J.Geophys.Res.,1977,82:2905～2930
[12]Van der Woerd J,Ryerson F,Tapponnier P,et al.Holocene left-slip rate determined by cosmogenic surface dating on the Xidatan segment of the Kunlunfault(Qinghai,China).Geology,1998,26(8):695～698
[13]吴珍汉,吴中海,胡道功等.青藏铁路沿线活动断裂与地质灾害图集.北京:地震出版社,2005Wu Z H,Wu Z H,Hu D G,et al.Picture Collection of Active Faults and Geological Hazards along Qinghai-Xizang Railway.Beijing:Seismological Press,2005
[14]Zhang P,Shen Z-K,Wang M,et al.Continuous deformation of the Tibetan Plateaufromglobal positioningsystemdata.Geology,2004,32(9):809～812
[15]Lu Z,Wright TJ,Wicks C,et al.Deformation of the2002Denali fault earthquakes,mapped by Radarsat-1interferometry.EOS,Transactions,American Geophysical Union,2003,84(425):430～431
[16]Velasco A A,Ammon C J,Beck S,et al.Broadband source modeling of the November8,1997,Tibet(Mw7.5)earthquake and itstectonic implications.J.Geophys.Res.,2000,105(B12):28065～28080
[17]Steck L K,Velasco A A,CogbillL A,et al.Improving regional seismic event locationin China.Pure Appl.Geophys.,2001,158:211～240
[18]许力生,陈运泰.1997年中国西藏玛尼Ms7.9地震的时空破裂过程.地震学报,1999,21(5):449～459Xu LS,Chen YT.Temporal-spatial rupture process of1997Mani,Tibet earthquake.Acta Seismological Sinica(in Chinese),1999,21(5):449～459
[19]Fialko Y,Simons M,AgnewD,et al.The complete(3-D)surface displacement field in the epicentral area of the1999Mw7.1Hecor Mine earthquake,California,from space geodetic observations.Geophys.Res.Lett.,2001,28(16):3063～3066
[20]徐锡伟.中国地震年鉴-藏北玛尼地震科学考察.北京:地震出版社,2000Xu X W.Yearbook of China Earthquake Research-Scientific Investigation of Mani Earthquake in North Tibet.Beijing:Seismological Press,2000
[21]Molnar P,Chen W P.Focal depths and fault plane solutions of earthquakes under the Tibetan plateau.J.Geophys.Res.,1983,88:1180～1196
[22]Shen Z-K,Zeng Y,Wang Y,et al.Post-seismic deformation modeling of the2001Kokoxili earthquake,eastern China.European Geophysical Society,Geophysical Research Abstracts,2003,(5):07840
[23]Le Pichon X,Kreemer C,Chamot-Rooke N.Asymmetry in elastic properties andthe evolution of large continental strike-slipfaults.J.Geophys.Res,2005,110,B03405,doi:10.102912004JB003343
[24]单新建,马瑾,王长林等.利用星载D-INSAR技术获取的地表形变场提取玛尼地震震源断层参数.中国科学(D辑),2002,32(10):837～844Shan XJ,Ma J,Wang CL,et al.Extractionof source parameters of Mani earthquake from D-INSAR deformation field.Science in China(Dseries)(in Chinese),2002,32(10):837～844
[25]Massonnet D,Feigl KL.Radar interferometry and its application to changes inthe earth s surface.Reviews ofGeophysics,1998,36(4):441～500
[26]Klinger Y,Xu X W,Tapponnier P,et al.High-resolution satellite imagery mapping of the surface rupture and slip distribution of the Mw7.8,14November2001Kokoxili earthquake,the Kunlun fault,northern Tibet,China.Bulletin of the Seismological Society of America,2005,95(5):1970～1987
[27]Guo J,Lin A,Maruyama T,et al.Newconstraints on recent large earthquakes along the Xidatan-Dongdatan segment of the Kunlun fault,Western China.Bulletin of the Seismological Society ofAmerica,2006,96(1):48～58
[28]Harris R A.Introduction to special section:Stress triggers,stress shadows,andimplicationsfor seismic hazard.Journal ofGeophysical Research-Solid Earth,1998,103(B10):24347～24358
[29]Fialko Y,Sandwell D,Simons M,et al.Three-dimensional deformation caused by the Bam,Iran,earthquake and the origin of shallowslip deficit.Nature,2005,435:295～299
[30]Farr T G,Kobrick M.Shuttle radar topography mission produces a wealth of data.Eos Trans.AGU,2000,81(48):583～585
[31]Rosen P,Hensley S,Joughin I,et al.Synthetic aperture radar interferometry.Proceedings ofthe IEEE,2000,88(3):333～382
[32]Scharroo R,Visser P.Precise orbit determination and gravity field improvement for the ERSsatellites.Journal ofGeophysical Research,1998,103(C4):8113～8127
[33]Brgmann R,Ayhan E,Fielding E,et al.Deformation duringthe12November1999,Dzce,Turkey Earthquake,from GPS and InSAR data.Bull.Seism.Soc.Am.,2002,92(1):161～171
[34]Chen C W.Statistical-cost network-flow approaches to two-dimensional phase unwrapping for radar interferometry[Ph.D.Thesis].Stanford University,2001
[35]Klinger Y,Michel R,King G,et al.Evidence for an earthquake barrier model fromMwsimilar to7.8Kokoxili(Tibet)earthquake slip-distribution.Earth and Planetary Science Letters,2006,242(3-4):354～364
[36]Okada Y.Surface deformation due to shear and tensile faults in ahalf-space.Bulletin ofthe Seismological Society of America,1985,75(4):1135～1154
[37]Wang R,Martin F,FrankRoth M,et al.Computation of deformation induced by earthquakes in a multi-layered elastic crust-FORTRAN programs EDGRN/EDCMP.Comp.Geosci.,2003,29:195～207
[38]Fialko Y.Probingthe mechanical properties of seismicallyactive crust with space geodesy:Study of the coseismic deformation due to the1992Mw7.3Landers(southern California)earthquake.Journal of Geophysical Research-Solid Earth,2004,109,B03307,doi:10.102912003JB002756
[39]Cervelli P,Murray M H,Segall P,et al.Estimating source parametersfromdeformation data,with an application to the March1997earthquake swarmoff the Izu Peninsula,Japan.J.Geophy.R.,2001,106(B6):11217～11237
[40]Jonsson S,Zebker H,Segall P,et al.Fault slip distribution of the1999Mw7.1Hector Mine,California,earthquake,estimated from satellite radar and GPS measurements.Bulletin ofthe Seismological SocietyofAmerica,2002,92(4):1377～1389
[41]MathWorks T.Optimization Toolbox for Use with MATLAB.The Mathworks Inc.,2006
[42]Hanssen R F.Radar Interferometry:Data Explanation and Error Analysis.Dordrecht,Kluwer Academic Publishers,2001
[43]Wright T J.Realistic Error Modeling for InSAR.ESA Fringe03Meeting,2003
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