当雄Ms6.6地震的InSAR观测及断层位错反演
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摘要
利用3景Envisat雷达遥感图像,获取了2008年10月6日西藏当雄Ms6.6地震的震前及同震形变场,结果表明,震前4个多月震中区未出现显著的地壳形变,只是地震造成震中区(20 km×20 km范围)最大近0.3 m的明显变形。形变场近南北轴向对称分布,西部沉降,东部隆升。利用均匀弹性半无限位错模型和约束非线性优化算法,对断层的位错量及分布的估算表明,地震以正断破裂为主,断面最大位错达3 m,震中位于90.374°E,29.745°N,震级Mw6.35;地震发生在走向189°、倾角60°的念青唐古拉山南东麓断裂带南段的次级断层上,发震断层长12 km,宽11 km,深度9.5 km,以东西向拉伸运动为主。较浅的震源深度与断层附近的地壳热状态有关。
Three scenes Envisat-1 images from ESA were used to derive the pre-seismic and coseismis deformation interfereograms caused by the Damxung Ms6.6 earthquake on Oct.6,2008,constrained by InSAR.The results indicate that InSAR could not detect notable crustal motion more than 4 months before the event which caused distinct displacement in an area of 20 km×20 km with a maximum LOS change about 0.3 m.The deformation field was symmetrically distributed and separated by a NS axis,where the west subsided and the east rose.We used a linear elastic dislocation model in half space and nonlinear constraint optimized algorithm to estimate the dislocation value and distribution of the fault.The results indicate that the epicenter locates at E90.374°,N29.745° with a seismic moment tensor Mw6.35.The earthquake is dominated by a normal fault fracture with the maximum slip of 3m on the 12 km×11 km rupture surface striking S189°W,dipping 60°to NW at the bottom of 9.5 km,located at a sub-fault of the southeastern piedmout of the Nyainqentanglha Mountains.The seismic fault extensionally moves along EW.The shallow depth of epicenter is related to crust thermal status of seismic region.
Three scenes Envisat-1 images from ESA were used to derive the pre-seismic and coseismis deformation interfereograms caused by the Damxung Ms6.6 earthquake on Oct.6,2008,constrained by InSAR.The results indicate that InSAR could not detect notable crustal motion more than 4 months before the event which caused distinct displacement in an area of 20 km×20 km with a maximum LOS change about 0.3 m.The deformation field was symmetrically distributed and separated by a NS axis,where the west subsided and the east rose.We used a linear elastic dislocation model in half space and nonlinear constraint optimized algorithm to estimate the dislocation value and distribution of the fault.The results indicate that the epicenter locates at E90.374°,N29.745° with a seismic moment tensor Mw6.35.The earthquake is dominated by a normal fault fracture with the maximum slip of 3m on the 12 km×11 km rupture surface striking S189°W,dipping 60°to NW at the bottom of 9.5 km,located at a sub-fault of the southeastern piedmout of the Nyainqentanglha Mountains.The seismic fault extensionally moves along EW.The shallow depth of epicenter is related to crust thermal status of seismic region.
引文
1吴中海,叶培盛,吴珍汉.2008年10月6日西藏当雄Ms6.6级强震的地震烈度控震构造和发震机理[J].地质通报,2009,28(6):713-725.
2 http://neic.usgs.gov/neis/eq_depot/2008/eq_081006_xva9/neic_xva9_cmt.html.
3吴章明,等.念青唐古拉山南东麓断层的初步研究[J].地震研究,1990,13(1):40-50.
4贺日政,高锐.西藏高原南北向裂谷研究意义[J].地球物理学进展,2003,18(1):35-43.
5 Kanamori H.The Energy Release in Great Earthquakes[J].J.Geophys.Res.,1977,82:2 981-2 987.
6国家地震局地质研究所.西藏中部活动断层[M].北京:地震出版社,1992.
7邓起东.中国活动构造图(1:400万)[M].北京:地震出版社,2007.
8 Massonnet D,et al.The displacement field of the Landersearthquake mapped by radar interferometry[J].Nature,1993,364:138-142
9 Massonnet D and Feigl K.Radar Interferometry And Its Ap-plication To Changes In The Earth’s Surface[J].Rev Geo-phys.,1998,36:441-500
10游新兆,等.大气折射对InSAR影响的定量分析[J].大地测量与地球动力学,2003,23(2):71-78.
11乔学军,游新兆,王琪.2008年1月9日西藏改则扎西错Ms6.9地震的InSAR实测形变场[J].自然科学进展,2009,19(2):173-179.
12孙建宝,等.东昆仑断裂玛尼段震间形变场的InSAR观测及断层滑动率初步估计[J].自然科学进展,2007,17(10):1 361-1 370
13乔学军,郭利民.新疆伽师强震群区的InSAR观测研究[J].大地测量与地球动力学,2007,27(1):7-13.
14 Farr T,et al.The shuttle radar topography mission[J].Rev.Geophys.,2007,45:RG2005,doi:10.1029/2005RG000172
15 Chen C and Zebker H.Network approaches to two-dimen-sional phase unwrapping:intractability and two new algo-rithms[J]J.Opt.Soc.Am.,2000,17:401-414.
16 Right T,Parsons B and England P.InSAR observations oflow slip rates on the major faults of western Tibet[J].Sci-ence,2004,305:236-239.
17 Azenave A and Valette C.Positioning results with DORISon SPOT2 after first year of mission[J].Geophys.Res.Lett.,1992:7 109-7 119.
18 Scharroo R and Visser P.Precise orbit determination andgravity field improvement for the ERS satellites[J].J.Geophys.Res.,1998,103:8 113-8 127.
19 Simons M,Fialko Y and Rivera L.Coseismic deformationfrom the 1999 Mw 7.1 Hector Mine,California,Earth-quake as Inferred from InSAR and GPS Observations[J].Bull.Seismol.Soc.Am.,2002,92:1 390-1 402.
20李振洪,刘经南,许才军.InSAR数据处理中的误差分析[J].武汉大学学报(信息科学版),2004,29(1):72-76.
21 Okada Y.Surface deformation due to shear and tensilefaults in a half-space[J].Bull.Seismol.Soc.Am.,1985,75:1 135-1 154
22 Brgmann R,et al.Postseismic strain following the 1989Loma Prieta earthquake from GPS and leveling measure-ments[J].J.Geophys.Res.,1997,102:4 933-4 955.
23吴珍汉,叶培盛,胡道功.青藏高原腹地的地壳变形与构造地貌形成演化过程[M].北京:地质出版社,2003.
24张国民,等.中国大陆地震震源深度及其构造含义[J].科学通报,2002,47(9):663-668.
25郑斯华.青藏高原地震的震源深度及其构造意义[J].中国地震,1995,11(2):99-106.
26 Chen W P and Molnar P.Focal depths of intracontinentaland intraplate earthquake and their implication for the ther-mal and mechanical properties of the lithosphere[J].Jour-nal of Geophysical Research,1983,88(B5):4 183-4214.
27胡圣标,汪集?.闽台地区最大震源深度与地表热流的关系[J].地震地质,1993,15(1):66-68.
28白嘉启,梅琳,杨美伶.青藏高原地热资源与地壳热结构[J].地质力学学报,2006,12(3):354-362.
29徐纪人,赵志新,石川有三.青藏高原中南部岩石圈扩张应力场与羊八井地热异常形成机制[J].地球物理学报,2005,48(4):861-869.
30韩同林.试论藏南活动构造与地热的关系[A].喜马拉雅地质Ⅱ[C].北京:地质出版社,1990.
31蒋长胜,吴忠良.由“重复地震”给出的中国地震台网的定位精度估计[J].中国地震,2005,21(2):147-154.
2 http://neic.usgs.gov/neis/eq_depot/2008/eq_081006_xva9/neic_xva9_cmt.html.
3吴章明,等.念青唐古拉山南东麓断层的初步研究[J].地震研究,1990,13(1):40-50.
4贺日政,高锐.西藏高原南北向裂谷研究意义[J].地球物理学进展,2003,18(1):35-43.
5 Kanamori H.The Energy Release in Great Earthquakes[J].J.Geophys.Res.,1977,82:2 981-2 987.
6国家地震局地质研究所.西藏中部活动断层[M].北京:地震出版社,1992.
7邓起东.中国活动构造图(1:400万)[M].北京:地震出版社,2007.
8 Massonnet D,et al.The displacement field of the Landersearthquake mapped by radar interferometry[J].Nature,1993,364:138-142
9 Massonnet D and Feigl K.Radar Interferometry And Its Ap-plication To Changes In The Earth’s Surface[J].Rev Geo-phys.,1998,36:441-500
10游新兆,等.大气折射对InSAR影响的定量分析[J].大地测量与地球动力学,2003,23(2):71-78.
11乔学军,游新兆,王琪.2008年1月9日西藏改则扎西错Ms6.9地震的InSAR实测形变场[J].自然科学进展,2009,19(2):173-179.
12孙建宝,等.东昆仑断裂玛尼段震间形变场的InSAR观测及断层滑动率初步估计[J].自然科学进展,2007,17(10):1 361-1 370
13乔学军,郭利民.新疆伽师强震群区的InSAR观测研究[J].大地测量与地球动力学,2007,27(1):7-13.
14 Farr T,et al.The shuttle radar topography mission[J].Rev.Geophys.,2007,45:RG2005,doi:10.1029/2005RG000172
15 Chen C and Zebker H.Network approaches to two-dimen-sional phase unwrapping:intractability and two new algo-rithms[J]J.Opt.Soc.Am.,2000,17:401-414.
16 Right T,Parsons B and England P.InSAR observations oflow slip rates on the major faults of western Tibet[J].Sci-ence,2004,305:236-239.
17 Azenave A and Valette C.Positioning results with DORISon SPOT2 after first year of mission[J].Geophys.Res.Lett.,1992:7 109-7 119.
18 Scharroo R and Visser P.Precise orbit determination andgravity field improvement for the ERS satellites[J].J.Geophys.Res.,1998,103:8 113-8 127.
19 Simons M,Fialko Y and Rivera L.Coseismic deformationfrom the 1999 Mw 7.1 Hector Mine,California,Earth-quake as Inferred from InSAR and GPS Observations[J].Bull.Seismol.Soc.Am.,2002,92:1 390-1 402.
20李振洪,刘经南,许才军.InSAR数据处理中的误差分析[J].武汉大学学报(信息科学版),2004,29(1):72-76.
21 Okada Y.Surface deformation due to shear and tensilefaults in a half-space[J].Bull.Seismol.Soc.Am.,1985,75:1 135-1 154
22 Brgmann R,et al.Postseismic strain following the 1989Loma Prieta earthquake from GPS and leveling measure-ments[J].J.Geophys.Res.,1997,102:4 933-4 955.
23吴珍汉,叶培盛,胡道功.青藏高原腹地的地壳变形与构造地貌形成演化过程[M].北京:地质出版社,2003.
24张国民,等.中国大陆地震震源深度及其构造含义[J].科学通报,2002,47(9):663-668.
25郑斯华.青藏高原地震的震源深度及其构造意义[J].中国地震,1995,11(2):99-106.
26 Chen W P and Molnar P.Focal depths of intracontinentaland intraplate earthquake and their implication for the ther-mal and mechanical properties of the lithosphere[J].Jour-nal of Geophysical Research,1983,88(B5):4 183-4214.
27胡圣标,汪集?.闽台地区最大震源深度与地表热流的关系[J].地震地质,1993,15(1):66-68.
28白嘉启,梅琳,杨美伶.青藏高原地热资源与地壳热结构[J].地质力学学报,2006,12(3):354-362.
29徐纪人,赵志新,石川有三.青藏高原中南部岩石圈扩张应力场与羊八井地热异常形成机制[J].地球物理学报,2005,48(4):861-869.
30韩同林.试论藏南活动构造与地热的关系[A].喜马拉雅地质Ⅱ[C].北京:地质出版社,1990.
31蒋长胜,吴忠良.由“重复地震”给出的中国地震台网的定位精度估计[J].中国地震,2005,21(2):147-154.
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