基于D-InSAR技术的西藏改则地震同震形变场特征分析
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摘要
2008年1月9日在西藏改则地区发生6.9级地震,接着1月16日又发生6.0级余震,表现为双震型。本文利用差分干涉测量技术(D-INSAR),通过对欧空局ASAR数据进行处理获取了其同震干涉形变场。通过分析表明:改则地震干涉形变场呈双贝壳状,影响范围约33 km×30 km,以北东向地震破裂带为分界线分为西北视线向沉降盘与东南视线向隆升盘,最大视线向沉降形变量约53.2 cm,最大视线向隆升形变量约11.3 cm。西北沉降盘又存在东、西两个形变中心,推测西部形变中心受6.0级余震的控制,东部形变中心受6.9级主震的控制。宏观震中位置应位于左旋走滑改则—洞错断裂与依布茶卡—日干配错断裂的分阶部位(左阶),构造应力场以张性拉伸为主,导致地震破裂为典型的正断层破裂,与此次地震的干涉形变场特征及哈佛大学震源机制解吻合。
On 9 January,2008,an MS6.9 earthquake happened in Gaize region(Tibet),with an MS6.0 aftershock on 16 January,it is a typical double-earthquake.This paper uses the ESA ASAR SLC data to analyse the coseismic deformation characteristics of the Gaize earthquake by the Differential Interferometric Synthetic Aperture Radar(D-InSAR).The analysis indicate that the interferogram is dual-shell shape,about 33 km×30 km in extension.And it is divided into two parts by the NE-direction earthquake rupture,the northwest slant range subsides and the southeast slant range ascends.The max slant range change subsides about 53.2 cm,the max slant range change ascends about 11.3 cm.There are two deformation centers at the northwest subside part.It is speculated that the west deformation center is controlled by the MS6.0 aftershock,and the east deformation center is controlled by the MS6.9 earthquake.The macroscopical seismic center is located at the apart position(left step) of Laevo strike slip fault of Gaize-Dongcuo fault and Yibuchaka-Riganpeicuo fault,the tensile stress of this apart position leads to the typical normal fault fracture of the Gaize earthquake,and this accords with the interferogram characteristics and the Harvard mechanism.
On 9 January,2008,an MS6.9 earthquake happened in Gaize region(Tibet),with an MS6.0 aftershock on 16 January,it is a typical double-earthquake.This paper uses the ESA ASAR SLC data to analyse the coseismic deformation characteristics of the Gaize earthquake by the Differential Interferometric Synthetic Aperture Radar(D-InSAR).The analysis indicate that the interferogram is dual-shell shape,about 33 km×30 km in extension.And it is divided into two parts by the NE-direction earthquake rupture,the northwest slant range subsides and the southeast slant range ascends.The max slant range change subsides about 53.2 cm,the max slant range change ascends about 11.3 cm.There are two deformation centers at the northwest subside part.It is speculated that the west deformation center is controlled by the MS6.0 aftershock,and the east deformation center is controlled by the MS6.9 earthquake.The macroscopical seismic center is located at the apart position(left step) of Laevo strike slip fault of Gaize-Dongcuo fault and Yibuchaka-Riganpeicuo fault,the tensile stress of this apart position leads to the typical normal fault fracture of the Gaize earthquake,and this accords with the interferogram characteristics and the Harvard mechanism.
引文
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[12]Rodriguez E,Morris C S,Belz J E,et al.An assessment of the SRTM topographic products[R].Technical Report JPL D-31639,Jet Propulsion Laboratory,Pasadena,California,2005,143.
[2]Peltzer G,Frederic Crampe,Gsofmy King.Evidence of Nonlinear Elasticity of the Crust from theMW7.6 Manyi(Tibet)Earthquake[J].Science,1999,286:272-276.
[3]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.
[4]单新建,张国宏.孕震区震前D-InSAR干涉形变场动态演化图像分析.地震地质,2006,28(3):441-446.
[5]Isabelle Ryder,Barry Parsons,Tim J.et al.Post-seismic motion following the 1997 Manyi(Tibet)earthquake:InSAR observations and modeling.Geophys.J.Int.(2007):1-19.
[6]马超,单新建.昆仑山口西MS8.1地震震源参数的多破裂段模拟研究[J].地球物理学报,2006,49(2):428-437.
[7]Lin A M,Fu B H,Gun J M,et al.Co-seismic strike-slip and rupture length produced by the 2001MS8.1 central Kunlun earthquake.Science,2002,296(14):2 015-2 017.
[8]王超,刘智,张红,等.张北一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):2 550-2 554.
[9]单新建,马谨,宋晓宇,等.利用星载D-INSAR技术获取的地表形变场研究张北-尚义地震震源破裂特征.中国地震,2002,18(2):119-126.
[10]Pathier E,Frnneau B,et al.Coseismic displacements of the footwall of the Chelungpu fault causedby the 1999,Taiwan,Chi-Chi earthquake from InSAR and GPS data[J].Earth Planet Sci Lett,2003,212:73-88.
[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]Rodriguez E,Morris C S,Belz J E,et al.An assessment of the SRTM topographic products[R].Technical Report JPL D-31639,Jet Propulsion Laboratory,Pasadena,California,2005,143.
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