西藏改则地震升降轨同震形变场特征分析与破裂模式
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摘要
通过升降轨ASAR数据的获取与差分干涉处理,获取了西藏改则地震的双视线向同震形变场信息。对升降轨同震形变场的特征分析表明,改则地震主、余震均表现为典型的正断裂破裂模式,并先后形成了东、西两条规模不同的走向NE、倾向NW的正断层破裂带(可能未出露地表),以及西北盘的东、西两个沉降形变中心。从干涉条纹的切割关系判断,东沉降形变中心可能受2008年1月9日Ms 6.9级主震的控制,西沉降形变中心可能受2008年1月16日Ms 6.0级余震的控制。Ms 6.9级主震形成东南盘隆升与西北盘沉降的总体格局;Ms 6.0级余震使西北盘余震震中及以西部位进一步沉降,造成西沉降中心沉降形变量大于东沉降中心。升降轨同震形变场的获取为进一步的震源参数模拟与三维形变场解算提供了更好的约束条件与信息。
Through differential interferometry of ascending and descending orbit ASAR data,the authors obtained the Double-LOS coseismic deformation fields of Gaize earthquake in Tibet.A characteristic analysis of coseismic deformation field indicates that the Ms 6.9 mainshock and Ms 6.0 aftershock both showed the typical model of normal fault and successively gave birth to east and west normal faulted fracture zones with different sizes probably at depth,trending NE and dipping NW,with the formation of east and west subsiding centers on the northwest plate.From the incising of interferometric stripes,it can be judged that the east and west subsiding centers are controlled respectively by January 9,2008 Ms 6.9 mainshock and January 16,2008 Ms 6.0 aftershock.The Ms 6.9 mainshock shaped the basic pattern of subsiding in the northwest plate and uplifting in the southeast plate.And the Ms 6.0 aftershock caused the further subsidence of the epicenter and the western part of the northwest plate;therefore,the subsidence value of the west subsiding center is larger than that of the east subsiding center.The obtaining of coseismic deformation fields of ascending-descending orbits has provided the better restriction and information for further hypocenter mechanism simulation and 3-D deformation field calculation.
Through differential interferometry of ascending and descending orbit ASAR data,the authors obtained the Double-LOS coseismic deformation fields of Gaize earthquake in Tibet.A characteristic analysis of coseismic deformation field indicates that the Ms 6.9 mainshock and Ms 6.0 aftershock both showed the typical model of normal fault and successively gave birth to east and west normal faulted fracture zones with different sizes probably at depth,trending NE and dipping NW,with the formation of east and west subsiding centers on the northwest plate.From the incising of interferometric stripes,it can be judged that the east and west subsiding centers are controlled respectively by January 9,2008 Ms 6.9 mainshock and January 16,2008 Ms 6.0 aftershock.The Ms 6.9 mainshock shaped the basic pattern of subsiding in the northwest plate and uplifting in the southeast plate.And the Ms 6.0 aftershock caused the further subsidence of the epicenter and the western part of the northwest plate;therefore,the subsidence value of the west subsiding center is larger than that of the east subsiding center.The obtaining of coseismic deformation fields of ascending-descending orbits has provided the better restriction and information for further hypocenter mechanism simulation and 3-D deformation field calculation.
引文
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[3]Peltzer G,Frederic Crampe,Gsofmy King.Evidence of NonlinearElasticity of the Crust from the Mw7.6 Manyi(Tibet)Earthquake[J].Science,1999,286:272-276.
[4]Massonnet D,Rossi M,Carmona C,et a1.The DisplacementField of the Landers Earthquake Mapped by Radar Interferometry[J].Nature,1993,364:138-142.
[5]Ingrid A Johanson,Eric J Fielding,Frederique Rolandone,et al.Coseismic and Postseismic Slip of the 2004 Parkfield EarthquakefromSpace-Geodetic Data.Bulletin of the Seismological Society ofAmerica[J].2006,96(4B):269-282.
[6]Tim J Wright,Zhong Lu,Chuck Wicks.Constraining the SlipDistribution and Fault Geometry of the Mw 7.9,3 November2002,Denali Fault Earthquake with Interferometric Synthetic Ap-erture Radar and Global Positioning System Data[J].Bulletin ofthe Seismological Society of America,2004,94(6B):175-189.
[7]Mark Simons,Yuri Fialko,Luis Rivera.Coseismic Deformationfrom the 1999 Mw7.1 Hector Mine,California,Earthquake as In-ferred from InSAR and GPS Observations[J].Bulletin of the Seis-mological Society of America,2002,92(4):1390?1402.
[8]Pathier E,Frnneau B,et a1.Coseismic Displacements of theFootwall of the Chelungpu Fault Caused by the 1999,Taiwan,Chi-Chi earthquake from InSAR and GPS data[J].Earth Planet.Sci.Lett.,2003,212:73-88.
[9]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[J].中国科学,2002,32(10):837-844.
[10]王超,刘智,张红,等.张北—尚义地震同震形变场雷达差分干涉测量[J].科学通报,2000,45(23):2550-2554.
[11]刘国祥,丁晓利,李志伟,等.ERS卫星雷达干涉测量:1999年台湾集集大地震震前和同震地表位移[J].地球物理学报,2002,45(增刊):165-174.
[12]Fialko Y,Simons M,Agnew D.The Complete(3-D)SurfaceDisplacement Field in the Epicentral Area of the 1999 Mw 7.1Hector Mine Earthquake,California,from Space Geodetic Obser-vations[J].Geophys.Res.Lett.,2001,28(16):3063-3066.
[13]Fialko Y,Sandwell D,Simons M.Three-dimensional Deforma-tion Caused by the Bam,Iran,Earthquake and the Origin of Shal-low Slip Deficit[J].Nature,2005,435:295-299.
[14]孙建宝,梁芳,徐锡伟,等.升降轨道ASAR雷达干涉提示的巴姆地震(Mw6.5)3D同震形变场[J].遥感学报,2006,10(4):489-496.
[15]Takada Y,Kobayashi T,Furuya M,et al.Coseismic Displace-ment due to the 2008 Iwate-Miyagi Nairiku Earthquake Detectedby ALOS/PALSAR:Preliminary Results[J].Earth Planets Space,2009,61:9-12.
[16]Rodriguez E,Morris C S,Belz J E,et al.An Assessment of theSRTM Topographic Products,Technical Report JPL D-31639[R].Jet Propulsion Laboratory,Pasadena,California,2005.
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