2008年M_S7.1于田地震InSAR同震形变场及其震源滑动反演
摘要
本研究利用InSAR技术与ALOS PALSAR雷达数据,获取了2008年3月20日于田M_S 7.1地震视线向同震形变场,并基于该数据集和限制性最小二乘算法反演了此次地震的断层滑动分布;通过构造四大类反演方案,详细分析了InSAR观测系统中的入射角与方位角对反演结果的影响.结果表明:入射角随点位变化对反演结果有较大影响,使用其平均值将对破裂细节产生一定影响;而方位角对反演结果的影响不大,使用其平均值是一种较为理想的选择;引入入射角与方位角变化后,反演获得了较佳的于田地震同震滑动,主要集中分布于0～14 km深度附近,最大滑动量达3.2 m,矩张量为3.3×10~(19)N·m,相当于矩震级M_W7.0.
We have obtained the coseismic deformation along line of sight of the 2008 Yutian earthquake,using ALOS PALSAR images and SAR interferomety technique.Based on the InSAR measurements and the constrained least square method,we studied the source parameters of this big normal event.Four schemes of inversion were constructed,with the emphasis on the effect to slip distribution inversion of the incidence angle and azimuth angle.Our inversion results show that the incidence angle has certain effect on the slip distribution,which means that a substitution of location-dependant incidence angle with constant mean incidence angle will lose some useful slip distribution on fault plane.Our inversion also shows the azimuth angle, however,has almost no obvious effect and it is an optimal choice to use the mean azimuth angle. Our most robust slip distribution can be obtained with the two parameters being location-dependant. In our favored inversion scheme using location dependant angles for both,the maximum slip reaches 3.2m.Slip is mainly confined to 0～14 km depth and no evidence of shallow slip deficit.The inverted seismic moment M? is 3.3×10~(19)N?m,equivalent to an event of magnitude M_W7.0.
We have obtained the coseismic deformation along line of sight of the 2008 Yutian earthquake,using ALOS PALSAR images and SAR interferomety technique.Based on the InSAR measurements and the constrained least square method,we studied the source parameters of this big normal event.Four schemes of inversion were constructed,with the emphasis on the effect to slip distribution inversion of the incidence angle and azimuth angle.Our inversion results show that the incidence angle has certain effect on the slip distribution,which means that a substitution of location-dependant incidence angle with constant mean incidence angle will lose some useful slip distribution on fault plane.Our inversion also shows the azimuth angle, however,has almost no obvious effect and it is an optimal choice to use the mean azimuth angle. Our most robust slip distribution can be obtained with the two parameters being location-dependant. In our favored inversion scheme using location dependant angles for both,the maximum slip reaches 3.2m.Slip is mainly confined to 0～14 km depth and no evidence of shallow slip deficit.The inverted seismic moment M? is 3.3×10~(19)N?m,equivalent to an event of magnitude M_W7.0.
引文
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[9]Delouis B,Giardini D,Lundgren P,et al.Joint inversion of InSAR,GPS,teleseismic,and strong-motion data for the spatial and temporal distribution of earthquake slip:Application to the 1999 Izmit Mainshock.Bull.Seism.Soc.Am.,2002,92 (1):278-299,doi:10.1785/0120000806
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[11]Steven N Ward,Gianlucar Valensise.Fault parameters and slip distribution of the 1915 Avezzano,Italy,earthquake derived from geodetic observations.Bulletin of the Seismological Society of America,1989,79(3):690-710
[12]Fukahata Y,Wright T J.A non-linear geodetic data inversion using ABIC for slip distribution on a fault with an unknown dip angle.Geophys.J.Int.,2008,173(2):353- 364,doi:10.1111/j.1365-246X.2007.03713.x
[13]Elliott J R,Walters R J,England P C,et al.Extension on the Tibetan plateau:recent normal faulting measured by InSAR and body wave seismology.Geophysical J.Int., 2010,183(2):503-535 doi:10.1111/j.1365-246X.2010. 04754
[14]万永革,沈正康,盛书中等.2008年新疆于田7.3级地震对周围断层的影响及其正断层机制的区域构造解释.地球物理学报,2010,53(2):280-289,DOI:10.3969/j.issn.0001- 5733.2010.02.006 Wan Y G,Shen Z K,Sheng S Z,et al.The mechanical effects of the 2008 M_s7.3 Yutian,Xinjiang earthquake on the neighboring faults and its tectonic origin of normal faulting mechanism.Chinese J.Geophys.(in Chinese),2010,53 (2):280-289,DOI:10.3969/j.issn.0001-5733.2010.02. 006
[15]Lohman R B,Simons M.Some thoughts on the use of InSAR data to constrain models of surface deformation:Noise structure and data downsampling.Geochem.Geophys.Geosyst.,2005,6: Q01007,doi:10.1029/2004GC000841
[16]Jonsson S,Zebker H,Segall P,et al.Fault slip distribution of the 1999 M_w7.1 Hector Mine,California,earthquake, estimated from satellite radar and GPS measurements. Bulletin of the Seismological Society of America,2002,92 (4):1377-1389
[17]Okada Y.Internal deformation due to shear and tensile faults in a half-space.Bull.Seism.Soc.Am.,1992,82(2):1018- 1040
[18]Wang R,Motagh M,Walter T R.Inversion of slip distribution from co-seismic deformation data by a sensitivitybased iterative fitting(SBIF)method.EGU General Assembly 2008,2008,10,EGU2008-A-07971
[19]Simons M,Fialko Y,Rivera L.Coseismic deformation from the 1999 M_w7.1 Hector Mine,California,Earthquake as inferred from InSAR and GPS observations.Bulletin of the Seismological Society of America,2002,92(4):1390- 1402,doi:10.1785/01200000933
[20]张国宏,屈春燕,宋小刚等.基于InSAR同震形变场反演汶川M_w7.9地震断层滑动分布.地球物理学报,2010,53(2): 269～279,DOI:10.3969/j.issn.0001-5733.2010.05.005 Zhang G H,Qu C Y,Song X G,et al.Slip distribution and source parameters inverted from co-seismic deformation derived by InSAR technology of wenchuan M_w7.9 earthquake. Chinese J.Geophys.(in Chinese),2010,53(2):269-279, DOI:10.3969/j.issn.0001-5733.2010.05.005
[21]Xu C J,Liu Y,Wen Y M,et al.Coseismic slip distribution of the 2008 M_w7.9 Wenchuan earthquake from joint inversion of GPS and InSAR Data.Bull.Seism.Soc.Am.,2010,100 (5B):2736-2749,doi:10.1785/0120090253
[2]Feigl K L,Sarti F,Vadon H,et al.Estimating slip distribution for the Izmit mainshock from coseismic GPS, ERS-1,RADARSAT,and SPOT measurements.Bull. Seism.Soc.Am.,2002,92(1):138-160,doi:10.1785/ 0120000830
[3]Lasserre G C,Peltzer F,Crampe,et al.Coseismic deformation of the 2001 M_w7.8 Kokoxili Earthquake in Tibet,measured by synthetic aperture radar interferometry. J.Geophys.Res.,2005,110:B12408,doi:10.1029/ 2004JB003500
[4]Funning G J,Parsons B,Wright T J.Fault slip in the 1997 Manyi,Tibet earthquake from linear elastic modelling of InSAR displacements.Geophys.J.Int.,2007,169(3):988- 1008
[5]Shen Z K,Sun J B,Zhang P Z,et al.Slip maxima at fault junctions and rupturing of barriers during the 2008 Wenchuan earthquake.Nature Geoscience,2009,2(10):718-724, doi:10.1038/nego636
[6]Feigl K L,Dupre E.RNGCHN:a program to calculate displacement components from dislocations in an elastic halfspace with applications for modeling geodetic measurements of crustal deformation.Computers and Geosciences,1999,25 (6):695-704
[7]马超,单新建.昆仑山M_s8.1地震震源参数的多破裂段模拟研究.地球物理学报,2006,49(2):428-437 Ma C,Shan X J.A multi-segment analytic modeling of hypocentral geometric characteristic parameters of the M_s8.1 earthquake at the Kunlun Mountains.Chinese J.Geophys. (in Chinese),2006,49(2):428-437
[8]孙建宝,徐锡伟,沈正康等.基于线弹性位错模型及干涉雷达同震形变场反演1997年玛尼M_w7.5级地震参数—Ⅰ.均匀滑动反演.地球物理学报,2007,50(4):1097-1110 Sun J B,Xu X W,Shen Z K,et al.Parameter inversion of the 1997 Mani earthquake from INSAR co-seismic deformation field based on linear elastic dislocation model-I.Uniform slip inversion.Chinese J.Geophys.(in Chinese),2007,50(4): 1097-1110
[9]Delouis B,Giardini D,Lundgren P,et al.Joint inversion of InSAR,GPS,teleseismic,and strong-motion data for the spatial and temporal distribution of earthquake slip:Application to the 1999 Izmit Mainshock.Bull.Seism.Soc.Am.,2002,92 (1):278-299,doi:10.1785/0120000806
[10]Motagh M,Wang R J,Walter T R,et al.Coseismic slip model of the 2007 August Pisco earthquake(Peru) as constrained by Wide Swath radar observations.Geophys.J.Int.,2008, 174(3):842-848
[11]Steven N Ward,Gianlucar Valensise.Fault parameters and slip distribution of the 1915 Avezzano,Italy,earthquake derived from geodetic observations.Bulletin of the Seismological Society of America,1989,79(3):690-710
[12]Fukahata Y,Wright T J.A non-linear geodetic data inversion using ABIC for slip distribution on a fault with an unknown dip angle.Geophys.J.Int.,2008,173(2):353- 364,doi:10.1111/j.1365-246X.2007.03713.x
[13]Elliott J R,Walters R J,England P C,et al.Extension on the Tibetan plateau:recent normal faulting measured by InSAR and body wave seismology.Geophysical J.Int., 2010,183(2):503-535 doi:10.1111/j.1365-246X.2010. 04754
[14]万永革,沈正康,盛书中等.2008年新疆于田7.3级地震对周围断层的影响及其正断层机制的区域构造解释.地球物理学报,2010,53(2):280-289,DOI:10.3969/j.issn.0001- 5733.2010.02.006 Wan Y G,Shen Z K,Sheng S Z,et al.The mechanical effects of the 2008 M_s7.3 Yutian,Xinjiang earthquake on the neighboring faults and its tectonic origin of normal faulting mechanism.Chinese J.Geophys.(in Chinese),2010,53 (2):280-289,DOI:10.3969/j.issn.0001-5733.2010.02. 006
[15]Lohman R B,Simons M.Some thoughts on the use of InSAR data to constrain models of surface deformation:Noise structure and data downsampling.Geochem.Geophys.Geosyst.,2005,6: Q01007,doi:10.1029/2004GC000841
[16]Jonsson S,Zebker H,Segall P,et al.Fault slip distribution of the 1999 M_w7.1 Hector Mine,California,earthquake, estimated from satellite radar and GPS measurements. Bulletin of the Seismological Society of America,2002,92 (4):1377-1389
[17]Okada Y.Internal deformation due to shear and tensile faults in a half-space.Bull.Seism.Soc.Am.,1992,82(2):1018- 1040
[18]Wang R,Motagh M,Walter T R.Inversion of slip distribution from co-seismic deformation data by a sensitivitybased iterative fitting(SBIF)method.EGU General Assembly 2008,2008,10,EGU2008-A-07971
[19]Simons M,Fialko Y,Rivera L.Coseismic deformation from the 1999 M_w7.1 Hector Mine,California,Earthquake as inferred from InSAR and GPS observations.Bulletin of the Seismological Society of America,2002,92(4):1390- 1402,doi:10.1785/01200000933
[20]张国宏,屈春燕,宋小刚等.基于InSAR同震形变场反演汶川M_w7.9地震断层滑动分布.地球物理学报,2010,53(2): 269～279,DOI:10.3969/j.issn.0001-5733.2010.05.005 Zhang G H,Qu C Y,Song X G,et al.Slip distribution and source parameters inverted from co-seismic deformation derived by InSAR technology of wenchuan M_w7.9 earthquake. Chinese J.Geophys.(in Chinese),2010,53(2):269-279, DOI:10.3969/j.issn.0001-5733.2010.05.005
[21]Xu C J,Liu Y,Wen Y M,et al.Coseismic slip distribution of the 2008 M_w7.9 Wenchuan earthquake from joint inversion of GPS and InSAR Data.Bull.Seism.Soc.Am.,2010,100 (5B):2736-2749,doi:10.1785/0120090253
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