基于线弹性位错模型反演1997年西藏玛尼Mw7.5级地震的干涉雷达同震形变场——Ⅱ滑动分布反演
|
摘要
1997年11月8日西藏Mw7.5级玛尼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.在第一部分中,我们应用广泛使用的Okada线弹性位错模型,假设断层的各个分段滑动量均匀,反演得到断层各个分段的几何参数和均匀滑动量.本部分的反演进一步去除滑动均匀假设,并利用更能反映断层真实状态的角形元位错模型(线弹性),在第一部分反演得到断层几何的基础上,反演断层面的静态位错分布.反演结果表明,线弹性滑动分布模型能够更好地解释观测数据,进一步提高反演的数据拟合程度.最终得到了断层面上的走滑和倾滑位错分布.首次得到的断层面滑动分布显示断层面滑动在浅部(0~12 km)比较集中,地震破裂长度约170 km,最大左旋走滑位移达4.8 m;反演结果还表明局部段落存在较大倾滑位移,量值达到1.9 m,这在断层模型中是不能忽略的,它可能是断层两侧形变不对称的原因之一;反演得到的标量地震矩为2.18×1020N.m,相当于矩震级Mw7.5,与Velasco等利用地震波形反演得到的结果一致.
The Nov.8,1997 Mani(Xizang) Mw7.5 earthquake is an important event since Synthetic Aperture Radar Interferometry was used for earthquake studies.In the first part we use the widely-used Okada linear elastic dislocation model and assume uniform slip on fault segments to invert the geometric parameters and the uniform slip.In this part we remove the uniform slip assumption,use more realistic angular dislocation model(linear elastic) to invert the static slip distribution on fault.The inversion result shows that this linear elastic slip distribution can explain the data better,and the goodness of fitting is improved further.We get both of the strike-slip distribution and the dip-slip distribution on the fault plane.The first-time acquired slip distribution indicates that the fault slip concentrates mainly in the shallow depth(0～12 km),the earthquake rupture is 170-km-long,the maximum left-lateral strike-slip is 4.8 m;the inversion result also shows that there are large dip-slip on some segments and their magnitude reaches 1.9 m,which can't be ignored in the inversion.The dip-slip may be one of the reasons of the asymmetric deformation pattern beside the two sides of the fault;the inverted seismic moment is 2.18×10~(20) N·m,equal to magnitude Mw7.5.It's consistent with the seismic waveform inversion of Velasco.
The Nov.8,1997 Mani(Xizang) Mw7.5 earthquake is an important event since Synthetic Aperture Radar Interferometry was used for earthquake studies.In the first part we use the widely-used Okada linear elastic dislocation model and assume uniform slip on fault segments to invert the geometric parameters and the uniform slip.In this part we remove the uniform slip assumption,use more realistic angular dislocation model(linear elastic) to invert the static slip distribution on fault.The inversion result shows that this linear elastic slip distribution can explain the data better,and the goodness of fitting is improved further.We get both of the strike-slip distribution and the dip-slip distribution on the fault plane.The first-time acquired slip distribution indicates that the fault slip concentrates mainly in the shallow depth(0～12 km),the earthquake rupture is 170-km-long,the maximum left-lateral strike-slip is 4.8 m;the inversion result also shows that there are large dip-slip on some segments and their magnitude reaches 1.9 m,which can't be ignored in the inversion.The dip-slip may be one of the reasons of the asymmetric deformation pattern beside the two sides of the fault;the inverted seismic moment is 2.18×10~(20) N·m,equal to magnitude Mw7.5.It's consistent with the seismic waveform inversion of Velasco.
引文
[1]Cervelli P,Murray M H,Segall P,Estimating source parametersfrom deformation data,with an application to the March 1997earthquake swarm off the Izu Peninsula,Japan.J.Geophy.R.,2001,106(B6):11217~11237
[2]Wright T J,Parsons B,England P C,et al.InSAR observations oflow slip rates on the major faults of western Tibet.Science,2004,305:236~239
[3]Fialko Y,Simons M,Agnew D,et al.The complete(3-D)surfacedisplacement field in the epicentral area of the 1999Mw7.1 HecorMine earthquake,California,from space geodetic observations.Geophys.Res.Lett.,2001,28(16):3063~3066
[4]Jonsson S,Zebker H,Segall P,et al.Fault slip distribution of the1999Mw 7.1 Hector Mine,California,earthquake,estimated fromsatellite radar and GPS measurements.Bulletin of the SeismologicalSociety ofAmerica,2002,92(4):1377~1389
[5]Bürgmann R,Ayhan E,Fielding E,et al.Deformation during the 12November 1999,Düzce,Turkey Earthquake,from GPS and InSARData.Bull.Seism.Soc.Am.,2002,92(1):161~171
[6]Okada Y.Surface deformation due to shear and tensile faults in ahalf-space.Bulletin of the Seismological Society of America,1985,75(4):1135~1154
[7]Okada Y.Internal deformation due to shear and tensile faults in ahalf-space.Bulletin of the Seismological Society of America,1992,82(2):1018~1040
[8]Wang R,Martin F,Roth F.Computation of deformation induced byearthquakes in a multi-layered elastic crust-FORTRAN programsEDGRN/EDCMP.Comp.Geosci.,2003,29:195~207
[9]Thomas A L.Poly3D:a three-dimensional,polygonal element,displacement discontinuity boundary element computer program withapplications to fractures,faults,and cavities in the Earth’s crust[Master thesis].Stanford University,1993
[10]Resor P G,Pollard D D,Wright T J,et al.Integrating high-precision aftershock locations and geodetic observations to modelcoseismic deformation associated with the 1995 Kozani-Grevenaearthquake,Greece.J.Geophys.Res.,2005,110(B09402),doi:10.1029/2004JB003263
[11]Massonnet D,Rossi M,Carmona C,et al.The displacement field ofthe Landers Earthquake mapped by Radar Interferometry.Nature,1993,364(6433):138~141
[12]Ferretti A,Prati C,Rocca F,et al.Permanent scatterers in SARinterferometry.IEEE Transactions on Geoscience and Remote Sensing,2001,39(1):8~20
[13]Burgmann R,Hilley G,Ferretti A,et al.Resolving vertical tectonicsin the San Francisco Bay Area from permanent scatterer InSAR andGPS analysis.Geology,2006,34(3):221~224
[14]Maerten F,Resor P G,Pollard D,et al.Invert for slip on three-dimensional fault surfaces using angular dislocations.Bull.Seism.Soc.Amer.,2005,95(5):1654~1665
[15]Comninou M A,Dunders J.The angular dislocation in a half-space.Journal of Elasticity,1975,5:203~216
[16]Jeyakumaran M,Rudnicki J W,Keer L M,et al.modeling slipzones with triangular dislocation elements.Bull.Seism.Soc.Am.,1992,82:2153~2169
[17]孙建宝.干涉雷达的地壳形变应用研究[博士学位论文].北京:北京师范大学,2005Sun J B.Crustal deformation application study by SAR Interferometry[Ph.D.Thesis](in Chinese).Beijing:Beijing Normal University,2005
[18]Desbrun M,Meyer M,Schroder P,et al.Implicit fairing of irregularmeshes using diffusion and curvature flow.ACM Proceedings ofSIGGRAPH,Los Angeles,1999
[19]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Mw7.5级地震参数—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 1997Mani earthquake from INSAR co-seismic deformation field based onlinear elastic dislocation model—I.Uniform slip inversion.ChineseJ.Geophys.(in Chinese),2007,50(4):1097~1110
[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-ScientificInvestigation of Mani Earthquake in North Tibet.Beijing:ChinaSeismological Press,2000
[21]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 ofground rupture earthquakes in seismic potential area of Chinese mainland.Earthquake Situation Research(in Chinese),2000,44(1):14~26
[22]Velasco A A,Ammon C J,Beck S L,et al.Broadband sourcemodeling of the November 8,1997,Tibet(Mw7.5)earthquake andits tectonic implications.J.Geophys.Res.,2000,105(B12):28065~28080
[23]Peltzer G,CrampéF,King G,et al.Evidence of nonlinear elasticityof the crust fromMw7.6 Manyi(Tibet)earthquake.Science,1999,286:273~276
[24]Lasserre C,Peltzer G,CrampéF,et al.Coseismic deformation of theMw=7.8 Kokoxili earthquake in Tibet measured by syntheticaperture radar interferometry.J.Geophys.Res.,2005,110(B12)(B12408),doi:10.1029/2004JB003500
[25]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 L S,Chen Y T.Temporal-spatial rupture process of 1997 Mani,Tibet earthquake.Acta Seismological Sinica(in Chinese),1999,21(5):449~459
[2]Wright T J,Parsons B,England P C,et al.InSAR observations oflow slip rates on the major faults of western Tibet.Science,2004,305:236~239
[3]Fialko Y,Simons M,Agnew D,et al.The complete(3-D)surfacedisplacement field in the epicentral area of the 1999Mw7.1 HecorMine earthquake,California,from space geodetic observations.Geophys.Res.Lett.,2001,28(16):3063~3066
[4]Jonsson S,Zebker H,Segall P,et al.Fault slip distribution of the1999Mw 7.1 Hector Mine,California,earthquake,estimated fromsatellite radar and GPS measurements.Bulletin of the SeismologicalSociety ofAmerica,2002,92(4):1377~1389
[5]Bürgmann R,Ayhan E,Fielding E,et al.Deformation during the 12November 1999,Düzce,Turkey Earthquake,from GPS and InSARData.Bull.Seism.Soc.Am.,2002,92(1):161~171
[6]Okada Y.Surface deformation due to shear and tensile faults in ahalf-space.Bulletin of the Seismological Society of America,1985,75(4):1135~1154
[7]Okada Y.Internal deformation due to shear and tensile faults in ahalf-space.Bulletin of the Seismological Society of America,1992,82(2):1018~1040
[8]Wang R,Martin F,Roth F.Computation of deformation induced byearthquakes in a multi-layered elastic crust-FORTRAN programsEDGRN/EDCMP.Comp.Geosci.,2003,29:195~207
[9]Thomas A L.Poly3D:a three-dimensional,polygonal element,displacement discontinuity boundary element computer program withapplications to fractures,faults,and cavities in the Earth’s crust[Master thesis].Stanford University,1993
[10]Resor P G,Pollard D D,Wright T J,et al.Integrating high-precision aftershock locations and geodetic observations to modelcoseismic deformation associated with the 1995 Kozani-Grevenaearthquake,Greece.J.Geophys.Res.,2005,110(B09402),doi:10.1029/2004JB003263
[11]Massonnet D,Rossi M,Carmona C,et al.The displacement field ofthe Landers Earthquake mapped by Radar Interferometry.Nature,1993,364(6433):138~141
[12]Ferretti A,Prati C,Rocca F,et al.Permanent scatterers in SARinterferometry.IEEE Transactions on Geoscience and Remote Sensing,2001,39(1):8~20
[13]Burgmann R,Hilley G,Ferretti A,et al.Resolving vertical tectonicsin the San Francisco Bay Area from permanent scatterer InSAR andGPS analysis.Geology,2006,34(3):221~224
[14]Maerten F,Resor P G,Pollard D,et al.Invert for slip on three-dimensional fault surfaces using angular dislocations.Bull.Seism.Soc.Amer.,2005,95(5):1654~1665
[15]Comninou M A,Dunders J.The angular dislocation in a half-space.Journal of Elasticity,1975,5:203~216
[16]Jeyakumaran M,Rudnicki J W,Keer L M,et al.modeling slipzones with triangular dislocation elements.Bull.Seism.Soc.Am.,1992,82:2153~2169
[17]孙建宝.干涉雷达的地壳形变应用研究[博士学位论文].北京:北京师范大学,2005Sun J B.Crustal deformation application study by SAR Interferometry[Ph.D.Thesis](in Chinese).Beijing:Beijing Normal University,2005
[18]Desbrun M,Meyer M,Schroder P,et al.Implicit fairing of irregularmeshes using diffusion and curvature flow.ACM Proceedings ofSIGGRAPH,Los Angeles,1999
[19]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Mw7.5级地震参数—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 1997Mani earthquake from INSAR co-seismic deformation field based onlinear elastic dislocation model—I.Uniform slip inversion.ChineseJ.Geophys.(in Chinese),2007,50(4):1097~1110
[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-ScientificInvestigation of Mani Earthquake in North Tibet.Beijing:ChinaSeismological Press,2000
[21]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 ofground rupture earthquakes in seismic potential area of Chinese mainland.Earthquake Situation Research(in Chinese),2000,44(1):14~26
[22]Velasco A A,Ammon C J,Beck S L,et al.Broadband sourcemodeling of the November 8,1997,Tibet(Mw7.5)earthquake andits tectonic implications.J.Geophys.Res.,2000,105(B12):28065~28080
[23]Peltzer G,CrampéF,King G,et al.Evidence of nonlinear elasticityof the crust fromMw7.6 Manyi(Tibet)earthquake.Science,1999,286:273~276
[24]Lasserre C,Peltzer G,CrampéF,et al.Coseismic deformation of theMw=7.8 Kokoxili earthquake in Tibet measured by syntheticaperture radar interferometry.J.Geophys.Res.,2005,110(B12)(B12408),doi:10.1029/2004JB003500
[25]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 L S,Chen Y T.Temporal-spatial rupture process of 1997 Mani,Tibet earthquake.Acta Seismological Sinica(in Chinese),1999,21(5):449~459
版权所有：© 2023 中国地质图书馆 中国地质调查局地学文献中心