基于SAR影像偏移量获取汶川地震二维形变场
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摘要
本文以ALOS卫星PALSAR影像为数据源,采用强度图像偏移量方法获得的整个汶川地震地表二维形变场显示,整个映秀—北川地表破裂带全长约240km,从西南端的虹口往北东方向一直延伸到青川县附近,在虹口及北川县城所在地为两个形变量最大区域,偏移量可达4～6m,局部更是达到了6～8m.在高川乡附近出现一斜列拉分阶区,宽约8～10km.在映秀—北川断层的地表破裂迹线南侧约12km处还有一条汉旺—白鹿次级破裂带,从漩口镇一直延伸到秀水镇,长度大约100km,在白鹿附近形变量较大,可达3～4m.另外在小鱼洞附近可见一个NW走向、长宽约10×5km、形变幅度达3～4m的连接以上两条破裂带的地表破裂带,性质为逆冲兼具左旋走滑.研究表明,利用SAR影像偏移量法能够获取近场几米量级的大形变量及客观揭示断层破裂迹线的真实形态和分段特征,可以成为野外观测、InSAR等手段的有益补充,综合以上几种观测手段,优势互补,我们可以构建更为真实的断层模型,进而对汶川地震的复杂破裂过程有更深入的了解.
In this paper,the sub-pixel offset-tracking method and ALOS image are used to map the Wenchuan earthquake rupture and to identify the faults activated by the earthquake.The results indicate that the Wenchuan earthquake produced at least two surface ruptures on the Longmenshan fault,the main rupture is named Beichuan—Yingxiu rupture(Longmenshan town—Gaochuan rupture in this map) and the secondary named Hanwang rupture.The former extends about 240 km along Longmenshan fault and is characterized by dextral-slip thrusting with horizontal displacement 4～6 m on average and a pull apart terrace about 8 km wide near Gaochuan town.The latter is 12 km south of the former,extending from Xuankou town to Xiushui town,about 100 km long.The maximum displacement about 3～4 m appears near Bailu town.A rupture named Xiaoyudong is located between the two ruptures before mentioned with NW-SE striking,and extends about 10 km,the maximum vertical displacement in this rupture is about 3～4 m.The research indicates that offset-tracking using SAR intensity image can be a powerful complement to differential radar interferometry and field research,which has severe limitations that are mainly due to data decorrelation and signal saturation,and it does not generally provide measurements in the near-fault area where large displacements occur.If we combine such methods together,a more realistic fault model can be established,which will contribute to the comprehension of the complicated rupture process in the Wenchuan earthquake.
In this paper,the sub-pixel offset-tracking method and ALOS image are used to map the Wenchuan earthquake rupture and to identify the faults activated by the earthquake.The results indicate that the Wenchuan earthquake produced at least two surface ruptures on the Longmenshan fault,the main rupture is named Beichuan—Yingxiu rupture(Longmenshan town—Gaochuan rupture in this map) and the secondary named Hanwang rupture.The former extends about 240 km along Longmenshan fault and is characterized by dextral-slip thrusting with horizontal displacement 4～6 m on average and a pull apart terrace about 8 km wide near Gaochuan town.The latter is 12 km south of the former,extending from Xuankou town to Xiushui town,about 100 km long.The maximum displacement about 3～4 m appears near Bailu town.A rupture named Xiaoyudong is located between the two ruptures before mentioned with NW-SE striking,and extends about 10 km,the maximum vertical displacement in this rupture is about 3～4 m.The research indicates that offset-tracking using SAR intensity image can be a powerful complement to differential radar interferometry and field research,which has severe limitations that are mainly due to data decorrelation and signal saturation,and it does not generally provide measurements in the near-fault area where large displacements occur.If we combine such methods together,a more realistic fault model can be established,which will contribute to the comprehension of the complicated rupture process in the Wenchuan earthquake.
引文
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[9]van Puymbroeck N,Michel R,Binet R,et al.Measuringearthquakes from optical satellite images.Applied Optics,2000,39(20):3486-3494.
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[11]Strozzi T,Wiesmann A,Sharov A,et al.Capabilities of L-band SAR Data for arctic Glacier Motion Estimation.2006IEEE International Symposium on Geoscience and RemoteSensing,2006:3816-3819.
[12]Gray A L,Mattar K E,Vachon P W,et al.InSAR resultsfrom the RADARSAT antarctic mapping mission data:estimation of glacier motion using a simple registrationprocedure.In IGARSS′98—1998 IEEE InternationalGeoscience and Remote Sensing Symposium,1998,3:1638-1640.
[13]Fialko Y,Simons M,Agnew D.The complete(3-D)surfacedisplacement field in the epicentral area of the 1999 Mw7.1Hector Mine earthquake,California,from space geodeticobservations.Geophys.Res.Lett.,2001,28(16):3063-3066.
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[15]Ge L L,Zhang K,ALex N,et al.Preliminary results ofsatellite radar differential interferometry for the co-seismicdeformation of the 12 May 2008 Ms8.0 Wenchuan earthquake.Geographic Information Sciences,2008,14(1):12-19.
[16]单新建,屈春燕,宋小刚等.汶川MS8.0级地震InSAR同震形变场观测与研究.地球物理学报,2009,52(3):496-504.Shan X J,Qu C Y,Song X G,et al.Coscismic surfacedeformation caused by the Wenchuan MS8.0earthquake fromInSAR data analysis.Chinese J.Geophys.(in Chinese),2009,52(2):496-504.
[17]Hashimoto M,Enomotoa M,Fukushima Y.Coseismicdeformation from the 2008 Wenchuan,China,earthquakederived from alos/palsar images.Tectonophysics,2010,491(1-4):59-71.
[18]Mattar K E,Gray A L.Reducing ionospheric electrondensity errors in satellite radar interferometry applications.Canadian Journal of Remote Sensing,2002,28(4):593-600.
[19]Gray A L,Mattar K E,Sofko G.Influence of ionosphericelectron density fluctuations on satellite radar interferometry.Geophysical Research Letters,2000,27(10):1451-1454.
[20]Wegmuller U,Werner C,Strozzi T,et al.Ionosphericelectron concentration effects on SAR and INSAR.2006IEEE International Symposium on Geoscience and RemoteSensing,2006:3731-3734.
[21]刘静,张智慧,文力等.汶川8级大地震同震破裂的特殊性及构造意义——多条平行断裂同时活动的反序型逆冲地震事件.地质学报,2008,82(12):1707-1722.Liu J,Zhang Z H,Wen L,et al.The Ms8.0 Wenchuanearthquake co-seismic rupture and its tectonic implications——anout-of-sequence thrusting event with slip partitioned onmultiple faults.Acta Geologica Sinica(in Chinese),2008,82(12):1707-1722.
[22]屈春燕,单新建,宋小刚等.D-InSAR技术应用于汶川地震地表位移场的空间分析.地震地质,2010,32(2):175-190.Qu C Y,Shan X J,Song X G,et al.Spatial analysis ofcoseismic displacement field of the Wenchuan Ms8.0Earthquake derived using D-InSAR.Seismology and Geology(in Chinese),2010,32(2):175-190.
[2]徐锡伟,闻学则,叶建青等.汶川Ms8.0地震地表破裂带及其发震构造.地震地质,2008,30(3):597-629.Xu X W,Wen X Z,Ye J Q,et al.The Ms8.0 Wenchuanearthquake surface ruptures and its seismogenic structure.Seismology and Geology(in Chinese),2008,30(3):597-629.
[3]李海兵,王宗秀,付小方等.2008年5月12日汶川地震(Ms8.0)地表破裂带的分布特征.中国地质,2008,35(5):803-813.Li H B,Wang Z X,Fu X F,et al.The surface rupture zonedistribution of the Wenchuan earthquake(Ms8.0)happenedon May 12th 2008.Geology in China.(in Chinese),2008,35(5):803-813.
[4]任俊杰,张世民.汶川8级地震地表破裂带特征及其构造意义.大地测量与地球动力学,2008,28(6):47-52.Ren J J,Zhang S M.Characteristics of surface rupture zoneof Wenchuan Ms8.0Earthquake and its tectonic significance.Journal of Geodesy and Geodynamics(in Chinese),2008,28(6):47-52.
[5]Shen Z K,Sun J B,Zhang P Z,et al.Slip maxima at faultjunctions and rupturing of barriers during the 2008Wenchuanearthquake.Nature Geoscience,2009,2(10):718-724.
[6]国家重大科学工程“中国地壳运动观测网络”项目组.GPS测定的2008年汶川Ms8.0级地震的同震位移场.中国科学(D),2008,38(10):1194-1206.National Scientific Project"China Crustal MovementObservation Network"Project Team.Coseismic displacements ofthe Ms8.0Wenchuan earthquake,2008observed by GPS.SciChina Ser D.(in Chinese),2008,38(10):1194-1206.
[7]Massonnet D,Rossi M,Carmona C.The displacement fieldof the Landers earthquake mapped by radar interferometry.Nature,1993,364(6433):138-142.
[8]Michel R,Avouac J,Taboury J.Measuring grounddisplacements from SAR amplitude images:Application tothe Landers Earthquake.Geophysical Research Letters,1999,26(7):875-878.
[9]van Puymbroeck N,Michel R,Binet R,et al.Measuringearthquakes from optical satellite images.Applied Optics,2000,39(20):3486-3494.
[10]Michel R,Avouac J P,Taboury J.Measuring near fieldcoseismic displacements from SAR images:Application to theLanders Earthquake.Geophysical Research Letters,1999,26(19):3017-3020.
[11]Strozzi T,Wiesmann A,Sharov A,et al.Capabilities of L-band SAR Data for arctic Glacier Motion Estimation.2006IEEE International Symposium on Geoscience and RemoteSensing,2006:3816-3819.
[12]Gray A L,Mattar K E,Vachon P W,et al.InSAR resultsfrom the RADARSAT antarctic mapping mission data:estimation of glacier motion using a simple registrationprocedure.In IGARSS′98—1998 IEEE InternationalGeoscience and Remote Sensing Symposium,1998,3:1638-1640.
[13]Fialko Y,Simons M,Agnew D.The complete(3-D)surfacedisplacement field in the epicentral area of the 1999 Mw7.1Hector Mine earthquake,California,from space geodeticobservations.Geophys.Res.Lett.,2001,28(16):3063-3066.
[14]Klinger Y,Michel R,King G.Evidence for an earthquakebarrier model from Mw7.8Kokoxili(Tibet)earthquake slip-distribution.Earth and Planetary Science Letters,2006,242(3-4):354-364.
[15]Ge L L,Zhang K,ALex N,et al.Preliminary results ofsatellite radar differential interferometry for the co-seismicdeformation of the 12 May 2008 Ms8.0 Wenchuan earthquake.Geographic Information Sciences,2008,14(1):12-19.
[16]单新建,屈春燕,宋小刚等.汶川MS8.0级地震InSAR同震形变场观测与研究.地球物理学报,2009,52(3):496-504.Shan X J,Qu C Y,Song X G,et al.Coscismic surfacedeformation caused by the Wenchuan MS8.0earthquake fromInSAR data analysis.Chinese J.Geophys.(in Chinese),2009,52(2):496-504.
[17]Hashimoto M,Enomotoa M,Fukushima Y.Coseismicdeformation from the 2008 Wenchuan,China,earthquakederived from alos/palsar images.Tectonophysics,2010,491(1-4):59-71.
[18]Mattar K E,Gray A L.Reducing ionospheric electrondensity errors in satellite radar interferometry applications.Canadian Journal of Remote Sensing,2002,28(4):593-600.
[19]Gray A L,Mattar K E,Sofko G.Influence of ionosphericelectron density fluctuations on satellite radar interferometry.Geophysical Research Letters,2000,27(10):1451-1454.
[20]Wegmuller U,Werner C,Strozzi T,et al.Ionosphericelectron concentration effects on SAR and INSAR.2006IEEE International Symposium on Geoscience and RemoteSensing,2006:3731-3734.
[21]刘静,张智慧,文力等.汶川8级大地震同震破裂的特殊性及构造意义——多条平行断裂同时活动的反序型逆冲地震事件.地质学报,2008,82(12):1707-1722.Liu J,Zhang Z H,Wen L,et al.The Ms8.0 Wenchuanearthquake co-seismic rupture and its tectonic implications——anout-of-sequence thrusting event with slip partitioned onmultiple faults.Acta Geologica Sinica(in Chinese),2008,82(12):1707-1722.
[22]屈春燕,单新建,宋小刚等.D-InSAR技术应用于汶川地震地表位移场的空间分析.地震地质,2010,32(2):175-190.Qu C Y,Shan X J,Song X G,et al.Spatial analysis ofcoseismic displacement field of the Wenchuan Ms8.0Earthquake derived using D-InSAR.Seismology and Geology(in Chinese),2010,32(2):175-190.
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