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.
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2013年第7期2280-2291,共12页
Chinese Journal of Geophysics
基金
“地震动力学”国家重点实验室自主课题(LED2010A02)和(LED2013A02)
地震行业专项(200708049)
国家自然科学基金(中韩合作)共同资助
关键词
玉树
同震
震后
INSAR
形变场演化
Yushu earthquake
Cosesimic
Postseismic
InSAR
Evolution of deformation field
