基于GPS和InSAR反演汶川Mw7.9地震断层滑动分布
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摘要
利用汶川8.0级地震野外考察得到的地表破裂带的空间分布及余震精定位结果,构建了两段发震断层的几何结构模型。基于该模型反演汶川8.0级地震GPS和InSAR同震形变场数据,获得了断层滑动分布及部分震源参数。结果表明:1)联合反演能较好地解释GPS和InSAR所获得的同震形变场,数据拟合度达97.27%;2)映秀-北川断裂反演得到的滑动分布主要集中于地下0～20km处,最大滑动量分别位于北川及青川等地区,尤其是多条断裂经过的北川地区在0～20km深处存在较大滑动量,最大可达到10m,青川地区10～15km深处的滑动量最高达6.5m;3)发震断层都以逆冲为主兼有一定右旋走滑分量,其中汶川地区的平均滑动角为103°,北川地区的平均滑动角为121°,青川地区的平均滑动角为138°,灌县-江油断裂的平均滑动角约为105°;4)反演得到的矩张量达8.7×1020Nm,矩震级为Mw7.9。
A two-segment fault model for the May 12,2008 Wenchuan Ms8.0 earthquake based on field investigations and precisely relocated aftershocks had established.The model is consistent with the surface rupture traces seen in the field at most sites along the fault.It contains two fractures with linearly varied dips from 70° to 33° and from 60° to 20°,respectively and they converge into one shear belt at the depth of 28 km.Then use this fault model as the constraint to invert the coseismic slip distribution using GPS data as well as InSAR measurements solo or jointly.The results show a robust slip distribution can be obtained by jointly using GPS and InSAR data.The deformation by forward modeling matches well the GPS data and InSAR deformation,with a relatively small total RMS of 9-11 cm.The inverted slip distribution is confined to a depth range 0-20 km and the maximum slip is 10 m.Among the largest slip areas,the Beichuan area has relatively concentrated slip and shallower depth(0-10 km)than other areas.This may be the reason that the Beichuan area was most severely destroyed by the earthquake.The inverted rake distribution shows that there is a transform of fault slide along the direction of SW-NE.It is primarily thrusting with some right-lateral component from nearby the epicenter to Beichuan,and changes into dominantly right-lateral slip with little thrusting or even pure right-lateral slip at the Qingchuan area in northeast.The mean rakes range from 103°to 121°and 138°.The inverted seismic moment tensor M0 is 8.7×1020 Nm,and the inverted moment magnitude scale Mw is 7.9.
A two-segment fault model for the May 12,2008 Wenchuan Ms8.0 earthquake based on field investigations and precisely relocated aftershocks had established.The model is consistent with the surface rupture traces seen in the field at most sites along the fault.It contains two fractures with linearly varied dips from 70° to 33° and from 60° to 20°,respectively and they converge into one shear belt at the depth of 28 km.Then use this fault model as the constraint to invert the coseismic slip distribution using GPS data as well as InSAR measurements solo or jointly.The results show a robust slip distribution can be obtained by jointly using GPS and InSAR data.The deformation by forward modeling matches well the GPS data and InSAR deformation,with a relatively small total RMS of 9-11 cm.The inverted slip distribution is confined to a depth range 0-20 km and the maximum slip is 10 m.Among the largest slip areas,the Beichuan area has relatively concentrated slip and shallower depth(0-10 km)than other areas.This may be the reason that the Beichuan area was most severely destroyed by the earthquake.The inverted rake distribution shows that there is a transform of fault slide along the direction of SW-NE.It is primarily thrusting with some right-lateral component from nearby the epicenter to Beichuan,and changes into dominantly right-lateral slip with little thrusting or even pure right-lateral slip at the Qingchuan area in northeast.The mean rakes range from 103°to 121°and 138°.The inverted seismic moment tensor M0 is 8.7×1020 Nm,and the inverted moment magnitude scale Mw is 7.9.
引文
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2Mahdi Motagh,et al.Coseismic slip model of the2007Au-gust Pisco earthquake(Peru)as constrained by wide swath radar observations[J].Geophys.J.Int.,2008,174:842-848.
3Okada Y.Internal deformation due to shear and tensile fault in a half-space[J].Bull.Seism.Soc.Am.,1992,82:1018-1040.
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7陈九辉,等.汶川Ms8.0地震余震序列重新定位及其地震构造研究[J].地球物理学报,2009,52(2):390-397.(Chen Jiuhui,et al.Seismotectonic study by relocation of the WenchuanMs8.0earthquake sequence[J].Chinese J.Geophys,2009,52(2):390-397)
8王卫民,等.四川汶川8.0级地震震源过程[J].地球物理学报,2008,51(5):1403-1410.(Wang Weimin,et al.Rupture process of theMs8.0Wenchuan earthquake of Si-chuan,China[J].Chinese J.Geophys,2008,51(5):1403-1410)
9张勇,等.2008年汶川大地震的时空破裂过程[J].中国科学D辑:地球科学,2008,38(10):1186-1194.(Zhang Yong,et al.Spatio-temporal rupture process of the2008great Wenchuan earthquake[J].Science in China Series D:Earth Sciences,2008,38(10):1186-1194)
10屈春燕,等.汶川Ms8.0地震InSAR同震形变场特征分析[J].地震地质,2008,30(4):1076-1084.(Qu Chun-yan,et al.Analysis on the characteristics of InSAR coseis-mic deformation of the MS8.0wenchuan earthquake[J].Seismology and Geology,2008,30(4):1076-1084)
11单新建,等.汶川Ms8.0地震InSAR同震形变场[J].地球物理学报,2009,52(2):496-504.(Shan Xinjian,et al.Coseismic surface deformation caused by the Wenchuan Ms8.0earthquake from InSAR data analysis[J].Chinese J.Geophys,2009,52(2):496-504)
12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地震的同震位移场[J].中国科学D辑:地球科学,2008,38(10):1195-1206.(Teamwork of the project“Crustal Movement Observation Network in China”.The coseismic deformation of the2008great WenchuanMs8.0earthquake measured by GPS[J].Science in China Series D:Earth Sciences,38(10):1195-1206)
13Wang R,Motagh M and Walter TR.Inversion of slip dis-tribution from co-seismic deformation data by a sensitivity-based iterative fitting(SBIF)method[J].EGUGeneral As-sembly2008,2008,10,EGU2008-A-07971.
14Yukitoshi Fukahata and Tim J Wright.Anon-linear geodet-ic data inversion using ABIC for slip distribution on a fault with an unknown dip angle[J].Geophys.J.Int.,2008,173:353-364.
15Shen Zhenkang,et al.Slip maxima at fault junctions and rupturing of barriers during the2008Wenchuan earthquake[J].Nature Geoscience,2009,2,718-724,doi:10.1038/nego636.
16Feng Guangcai,et al.Coseismic fault slip of the2008Mw7.9Wenchuan earthquake estimated from InSAR and GPS measurements[J].Geophysical Research Letters,2010,37,L01302,doi:10.1029/2009GL041213
17Garth J Funning,Barry Parsons and Tim J Wright.Fault slip in the1997Manyi,Tibet earthquake from linear elastic modelling of InSAR displacements[J].Geophys.J.Int.,2007,169:988-1008.
2Mahdi Motagh,et al.Coseismic slip model of the2007Au-gust Pisco earthquake(Peru)as constrained by wide swath radar observations[J].Geophys.J.Int.,2008,174:842-848.
3Okada Y.Internal deformation due to shear and tensile fault in a half-space[J].Bull.Seism.Soc.Am.,1992,82:1018-1040.
4张培震,等.2008年汶川8.0级地震发震断裂带滑动速率、复发周期和构造成因[J].地球物理学报,2008,51(4):1066-1073.(Zhang Peizhen,et al.Slip rates and re-currence intervals of the Longmenshan active fault zone,and tectonic implications for the mechanism of the May12Wen-chuan earthquake,2008,Sichuan,China[J].Chiese J.Geophys,2008,51(4):1066-1073)
5徐锡伟,等.汶川Ms8.0地震地表破裂带及其发震构造[J].地震地质,2008,30(3):597-629.(Xu Xiwei,et al.TheMs8.0Wenchuan earthquake surface ruptures and its seismogenic structure[J].Seismology and Geology,2008,30(3):597-629)
6何宏林,等.汶川Ms8.0地震地表破裂带[J].地震地质,2008,30(2):359-362.(He Honglin,et al.Rupture of the Ms8.0Wenchuan earthquake along Baishanhe river[J].Seismology and Geology,2008,30(2):359-362)
7陈九辉,等.汶川Ms8.0地震余震序列重新定位及其地震构造研究[J].地球物理学报,2009,52(2):390-397.(Chen Jiuhui,et al.Seismotectonic study by relocation of the WenchuanMs8.0earthquake sequence[J].Chinese J.Geophys,2009,52(2):390-397)
8王卫民,等.四川汶川8.0级地震震源过程[J].地球物理学报,2008,51(5):1403-1410.(Wang Weimin,et al.Rupture process of theMs8.0Wenchuan earthquake of Si-chuan,China[J].Chinese J.Geophys,2008,51(5):1403-1410)
9张勇,等.2008年汶川大地震的时空破裂过程[J].中国科学D辑:地球科学,2008,38(10):1186-1194.(Zhang Yong,et al.Spatio-temporal rupture process of the2008great Wenchuan earthquake[J].Science in China Series D:Earth Sciences,2008,38(10):1186-1194)
10屈春燕,等.汶川Ms8.0地震InSAR同震形变场特征分析[J].地震地质,2008,30(4):1076-1084.(Qu Chun-yan,et al.Analysis on the characteristics of InSAR coseis-mic deformation of the MS8.0wenchuan earthquake[J].Seismology and Geology,2008,30(4):1076-1084)
11单新建,等.汶川Ms8.0地震InSAR同震形变场[J].地球物理学报,2009,52(2):496-504.(Shan Xinjian,et al.Coseismic surface deformation caused by the Wenchuan Ms8.0earthquake from InSAR data analysis[J].Chinese J.Geophys,2009,52(2):496-504)
12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地震的同震位移场[J].中国科学D辑:地球科学,2008,38(10):1195-1206.(Teamwork of the project“Crustal Movement Observation Network in China”.The coseismic deformation of the2008great WenchuanMs8.0earthquake measured by GPS[J].Science in China Series D:Earth Sciences,38(10):1195-1206)
13Wang R,Motagh M and Walter TR.Inversion of slip dis-tribution from co-seismic deformation data by a sensitivity-based iterative fitting(SBIF)method[J].EGUGeneral As-sembly2008,2008,10,EGU2008-A-07971.
14Yukitoshi Fukahata and Tim J Wright.Anon-linear geodet-ic data inversion using ABIC for slip distribution on a fault with an unknown dip angle[J].Geophys.J.Int.,2008,173:353-364.
15Shen Zhenkang,et al.Slip maxima at fault junctions and rupturing of barriers during the2008Wenchuan earthquake[J].Nature Geoscience,2009,2,718-724,doi:10.1038/nego636.
16Feng Guangcai,et al.Coseismic fault slip of the2008Mw7.9Wenchuan earthquake estimated from InSAR and GPS measurements[J].Geophysical Research Letters,2010,37,L01302,doi:10.1029/2009GL041213
17Garth J Funning,Barry Parsons and Tim J Wright.Fault slip in the1997Manyi,Tibet earthquake from linear elastic modelling of InSAR displacements[J].Geophys.J.Int.,2007,169:988-1008.
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