2010年青海玉树地震同震-震后形变场特征及演化过程
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摘要
基于星载合成孔径雷达差分干涉测量技术(DInSAR)和4期ENVISAT/ASAR雷达数据,获得了不同时间基线的三个同震干涉形变场和两个震后干涉形变场,并对这五个在时段上互有重叠的形变场进行了综合分析.结果表明,玉树地震同震形变场为围绕发震断层NW展布的椭圆形干涉条纹,覆盖范围约89km×59km.断层运动性质为左旋走滑.两盘最大视线向相对形变量至少达45cm,最大形变出现在结古镇附近.时间基线不同的同震形变场总体上基本一致,但两盘最大相对形变量和局部形变存在差异.震后时间较长的干涉对反映的最大形变量反而减小;在震后时间较短的干涉对上于结古镇西南侧观测到的局部形变,在震后时间较长的干涉对上却没有出现.分析认为在形变量最大的结古镇附近可能出现了震后快速弹性回弹,导致随震后时间延续,形变量反而减小的现象.玉树地震震后形变主要出现在断层附近、震后不久的时段内,形变量在8cm以下,具有与同震方向一致和相反的两种震后形变方式.在结古镇西南观测到一个与同震形变相反的局部沉降,应为震后弹性回弹.在微观震中处的断层附近观测到与同震方向一致的震后形变,可能是震后余滑.通过对地震前后不同时间基线的多个干涉对的联合对比分析,可以在一定程度上区分同震形变与震后形变,更好地研究地震引起的变形过程,特别是地震断层附近短期震后形变场的演化过程,为进一步研究断层带的岩性特征、物理力学及运动特性提供约束.
Using D-InSAR technology and 4 scenes of ENVISAT/ASAR radar data,we obtain 3 coseismic deformation fields and 2 postseismic deformation fields on different time intervals of the 2010 Yushu,Qinghai MS7.1 earthquake and analyze these five temporally overlapped fields.The results show that the coseismic deformation fields of this event exhibit NW-trending elliptic fringes surrounding the seismogenic fault,which cover an area of about 89 km by 59 km.They indicate left-slip faulting with relative displacement between the two sides of the fault in line of sight at least 45cm,the maximum appearing nearby the Jiegu town.The coseismic deformation fields on different time baselines are largely consistent,though having some discrepancies in the maximum value and local relative displacements.The maximum displacement derived from coseismic interferograms with a long time after the earthquake became smaller.The local deformation observed southwest of the Jiegu town from coseismic interferograms with a short time after the event does not appear on the interferograms with the long time after the quake.The reason for this difference is probably due to rapid elastic rebound near the Jiegu town after the event.There are two kinds of postseismic deformation fields around the fault with displacement less than 8 cm.One is local subsidence southwest of the Jiegu town,opposite to the coseismic deformation in motion sense,which might be elastic rebound after the earthquake.The other is the displacement near the instrumental epicenter,consistent with the sense of the coseismic deformation,likely the after-slip of the fault.This study demonstrates that comparative analysis to multiple interferograms on different time baselines before and after the earthquake can facilitate distinguishing coseismic and postseismic deformations,and researching into deformation processes caused by the earthquake,especially the evolution processes of postseismic deformation fields in a short time after the event.The results of such an analysis can provide constraints for studies of lithology,physical properties and kinetic features of the fault.
Using D-InSAR technology and 4 scenes of ENVISAT/ASAR radar data,we obtain 3 coseismic deformation fields and 2 postseismic deformation fields on different time intervals of the 2010 Yushu,Qinghai MS7.1 earthquake and analyze these five temporally overlapped fields.The results show that the coseismic deformation fields of this event exhibit NW-trending elliptic fringes surrounding the seismogenic fault,which cover an area of about 89 km by 59 km.They indicate left-slip faulting with relative displacement between the two sides of the fault in line of sight at least 45cm,the maximum appearing nearby the Jiegu town.The coseismic deformation fields on different time baselines are largely consistent,though having some discrepancies in the maximum value and local relative displacements.The maximum displacement derived from coseismic interferograms with a long time after the earthquake became smaller.The local deformation observed southwest of the Jiegu town from coseismic interferograms with a short time after the event does not appear on the interferograms with the long time after the quake.The reason for this difference is probably due to rapid elastic rebound near the Jiegu town after the event.There are two kinds of postseismic deformation fields around the fault with displacement less than 8 cm.One is local subsidence southwest of the Jiegu town,opposite to the coseismic deformation in motion sense,which might be elastic rebound after the earthquake.The other is the displacement near the instrumental epicenter,consistent with the sense of the coseismic deformation,likely the after-slip of the fault.This study demonstrates that comparative analysis to multiple interferograms on different time baselines before and after the earthquake can facilitate distinguishing coseismic and postseismic deformations,and researching into deformation processes caused by the earthquake,especially the evolution processes of postseismic deformation fields in a short time after the event.The results of such an analysis can provide constraints for studies of lithology,physical properties and kinetic features of the fault.
引文
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[9]江在森,马宗晋,张希等.GPS初步结果揭示的中国大陆水平应变场与构造变形.地球物理学报,2003,46(3):352-358.Jiang Z S,Ma Z J,Zhang X,Wang,et al.Horizontal strainfield and tectonic deformation of china mainland revealed bypreliminary GPS result.Chinese J.Geophys.(in Chinese),2003,46(3):352-358.
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[11]沈强,乔学军,王琪等.中国玉树MW6.9地震InSAR地表形变特征分析.大地测量与地球动力学,2010,30(3):5-9.Shen Q,Qiao X J,Wang Q,et al.Characteristic analysis ofcoseismic deformation of Yushu MW6.9 earthquake fromInSAR images.Journal of Geodesy and Geodynamics(inChinese),2010,30(3):5-9.
[12]Li Z H,Elliott J R,Feng W P,et al..The 2010 Mw6.8Yushu(Qinghai,China)earthquake:Constraints providedby InSAR and body wave seismology.J.Geophys.Res.,2011,116(B10):B10302,doi:10.1029/2011JB008358.
[13]Tobita M,Nishimura T,Kobayashi T,et al.Estimation ofcoseismic deformation and a fault model of the 2010Yushuearthquake using PALSAR interferometry data.Earth andPlanetary Science Letters,2011,307(3-4):430-438,doi:10.1016/j.epsl.2011.05.017.
[14]Zha X J,Dai Z Y,Ge L L,et al.Fault geometry and slipdistribution of the 2010 Yushu earthquakes inferred fromInSAR measurement.Bulletin of the Seismological Societyof America,2011,101(4):1951-1958,doi:10.1785/0120100192.
[15]Shan X J,Ma J,Wang C L,et al.Co-seismic grounddeformation and source Parameters of Mani M7.9earthquakeinferred from Spaceborne D-InSAR observation data.Sciencein China(Series D),2004,47(6):481-488.
[16]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,doi:10.1038/NGEO636.
[17]Qu C Y,Shan X J,Zhang G H,et al.Coseismicdisplacement field of the Wenchuan Ms8.0earthquake in 2008derived using differential radar interferometry.Journal ofApplied Remote Sensing,2010,4(1):043516,doi:10.1117/12.866087.
[18]郭华东.雷达对地观测理论与应用.北京:科学出版社.2000.Guo H D.The Theory and Application of Radar EarthObservation(in Chinese).Beijing:Science Press,2000.
[19]罗三明,杨国华,董运洪等.利用PSInSAR时间序列研究拉奎拉地震位移场变化特征.地球物理学进展,2012,27(4):1307-1315.Luo S M,Yang G H,Dong Y H,et al.Researchdisplacement field characteristics on L′Aquila earthquake fromPSInSAR time series.Progress in Geophys.(in Chinese),2012,27(4):1307-1315.
[20]冯万鹏,李振洪,李春来.利用InSAR确定2009年4月6日Mw6.3拉奎拉(Italy)地震最优震源模型.地球物理学进展,2010,25(5):1550-1559.Feng W P,Li Z H,Li C L.Optimal source parameters of the6April 2009 Mw6.3L′Aquila,Italy earthquake from InSARobservations.Progress in Geophys.(in Chinese),2010,25(5):1550-1559.
[21]丁伟,汪长城,李志伟等.基于改进LAMBDA方法的PSInSAR相位解缠.地球物理学进展,2011,26(5):1839-1848.Ding W,Wang C C,Li Z W et al.An improved LAMBDAmethod for PSInSAR phase unwrapping.Progress in Geophys.(in Chinese),2011,26(5):1839-1848.
[2]陈立春,王虎,冉永康等.玉树MS7.1级地震地表破裂与历史大地震.科学通报,2010,55(13):1200-1205.Chen L C,Wang H,Ran Y K,et al.The Ms7.1 Yushuearthquake surface rupture and large historical earthquakeson the Garzê-Yushu Fault.Chinese Sci.Bull.,2010,55(31):3504-3509,doi:10.1007/s11434-010-4079-2.
[3]李闽峰,邢成起,蔡长星等.玉树断裂活动性研究.地震地质,1995,17(3):218-224.Li M F,Xing C Q,Cai C X,et al.Research on activity ofYuShu fault.Seismology and Geology(in Chinese),1995,17(3):218-224.
[4]张培震,邓起东,张国民等.中国大陆的强震活动与活动地块.中国科学D辑:地球科学,2003,33(增刊):12-20.Zhang P Z,Deng Q D,Zhang G M,et al.Active tectonicblocks and strong earthquakes in the continent of China.Sci.China Der.D-Earth Sci.,2003,46(S2):13-24.
[5]闻学泽,徐锡伟,郑荣章等.甘孜—玉树断裂的平均滑动速率与近代大地震破裂.中国科学D辑:地球科学,2003,33(增刊):199-208.Wen X Z,Xu X W,Zheng R Z,et al.Average ship-rate andrecent large earthquake ruptures along the Garzê-YushuFault.Sci.China Ser.D-Earth.Sci.,2003,46(1):276-288.
[6]彭华,马秀敏,白嘉启等.甘孜玉树断裂带第四纪活动特征.地质力学学报,2006,12(3):295-304.Peng H,Ma X M,Bai J Q,et al.Characteristics ofquaternary activities of the Garzê-Yushu fault zone.Journalof Geomechanics(in Chinese),2006,12(3):295-304.
[7]张永志,崔笃信,王琪等.利用GPS资料研究区域地壳应力场变化与地震活动关系.地震学报,2000,22(5):449-456.Zhang Y Z,Cui D X,Wang Q,et al.Relationship betweenregional stress field variation and earthquake activities fromGPS data.Acta Seismologica Sinica(in Chinese),22(5):449-456.
[8]王小亚,朱文耀,符养等.GPS监测的中国及其周边现时地壳形变.地球物理学报,2002,45(2):198-209.Wang X Y,Zhu W Y,Fu Y,et al.Present-time crustaldeformation in china and its surrounding regions by GPS.Chinese J.Geophys.(in Chinese),2002,45(2):198-209.
[9]江在森,马宗晋,张希等.GPS初步结果揭示的中国大陆水平应变场与构造变形.地球物理学报,2003,46(3):352-358.Jiang Z S,Ma Z J,Zhang X,Wang,et al.Horizontal strainfield and tectonic deformation of china mainland revealed bypreliminary GPS result.Chinese J.Geophys.(in Chinese),2003,46(3):352-358.
[10]郭华东,王心源,李新武等.多模式SAR玉树地震协同分析.科学通报,2010,55(13):1195-1199.Guo H D,Wang X Y,Li X W,et al.Yushu earthquakesynergic analysis using multimodal SAR datasets.ChineseSci.Bull.,2010,55(31):3499-3503,doi:l0.1007/s11434.010-4078-3.
[11]沈强,乔学军,王琪等.中国玉树MW6.9地震InSAR地表形变特征分析.大地测量与地球动力学,2010,30(3):5-9.Shen Q,Qiao X J,Wang Q,et al.Characteristic analysis ofcoseismic deformation of Yushu MW6.9 earthquake fromInSAR images.Journal of Geodesy and Geodynamics(inChinese),2010,30(3):5-9.
[12]Li Z H,Elliott J R,Feng W P,et al..The 2010 Mw6.8Yushu(Qinghai,China)earthquake:Constraints providedby InSAR and body wave seismology.J.Geophys.Res.,2011,116(B10):B10302,doi:10.1029/2011JB008358.
[13]Tobita M,Nishimura T,Kobayashi T,et al.Estimation ofcoseismic deformation and a fault model of the 2010Yushuearthquake using PALSAR interferometry data.Earth andPlanetary Science Letters,2011,307(3-4):430-438,doi:10.1016/j.epsl.2011.05.017.
[14]Zha X J,Dai Z Y,Ge L L,et al.Fault geometry and slipdistribution of the 2010 Yushu earthquakes inferred fromInSAR measurement.Bulletin of the Seismological Societyof America,2011,101(4):1951-1958,doi:10.1785/0120100192.
[15]Shan X J,Ma J,Wang C L,et al.Co-seismic grounddeformation and source Parameters of Mani M7.9earthquakeinferred from Spaceborne D-InSAR observation data.Sciencein China(Series D),2004,47(6):481-488.
[16]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,doi:10.1038/NGEO636.
[17]Qu C Y,Shan X J,Zhang G H,et al.Coseismicdisplacement field of the Wenchuan Ms8.0earthquake in 2008derived using differential radar interferometry.Journal ofApplied Remote Sensing,2010,4(1):043516,doi:10.1117/12.866087.
[18]郭华东.雷达对地观测理论与应用.北京:科学出版社.2000.Guo H D.The Theory and Application of Radar EarthObservation(in Chinese).Beijing:Science Press,2000.
[19]罗三明,杨国华,董运洪等.利用PSInSAR时间序列研究拉奎拉地震位移场变化特征.地球物理学进展,2012,27(4):1307-1315.Luo S M,Yang G H,Dong Y H,et al.Researchdisplacement field characteristics on L′Aquila earthquake fromPSInSAR time series.Progress in Geophys.(in Chinese),2012,27(4):1307-1315.
[20]冯万鹏,李振洪,李春来.利用InSAR确定2009年4月6日Mw6.3拉奎拉(Italy)地震最优震源模型.地球物理学进展,2010,25(5):1550-1559.Feng W P,Li Z H,Li C L.Optimal source parameters of the6April 2009 Mw6.3L′Aquila,Italy earthquake from InSARobservations.Progress in Geophys.(in Chinese),2010,25(5):1550-1559.
[21]丁伟,汪长城,李志伟等.基于改进LAMBDA方法的PSInSAR相位解缠.地球物理学进展,2011,26(5):1839-1848.Ding W,Wang C C,Li Z W et al.An improved LAMBDAmethod for PSInSAR phase unwrapping.Progress in Geophys.(in Chinese),2011,26(5):1839-1848.
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