Interseismic Strain Along the Northern Edge of Tibet Using SAR Interferometry

利用 SAR 干涉测量西藏北部边缘的震间应变

• 批准号: 0125688
• 负责人: Gilles Peltzer
• 金额: $ 32.1万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-06-15 至 2007-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0125688&HistoricalAwards=false
• 关键词: Interseismic; Strain; Along; Northern; Edge

The current rate of strain concentrated along the Altyn Tagh and Kunlun fault systems in northern Tibet is being determined using the technique of radar interferometry. These fault systems play a key role in the dynamics of the continental deformation in Asia, yet their slip rate and associated deformation are still poorly known. Currently debated issues include the respective amounts of the convergence between India and Asia that are absorbed by crustal thickening and by lateral extrusion of continental blocks, or the characterization of the distribution of deformation throughout the continent. These issues are unresolved because of the poor knowledge of the present-day kinematics in the collision zone. In addition, northern Tibet has been the locus of two large earthquakes in 1997 and 2001 producing a disruption in the current inter-seismic strain pattern in the northern part of the collision zone.Spatially continuous maps of the line of sight displacement of the ground along active fault zones are being constructed by interferometric processing of synthetic aperture radar (SAR) data. This research exploits the extensive archive of ERS SAR data covering the northern Tibet area that have been acquired by the European Space Agency since 1992. Errors in the data due to poor orbit determination and troposphere phase propagation delay are reduced using a baseline re-estimation procedure and data averaging, following the approach developed with radar data of California. Line of sight displacement maps are then combined to constrain deformation process models of long-term fault creep and of co-seismic slip and post-seismic relaxation for the 1997 and 2001 events. The data are used to determine distribution of inter-seismic strain in the vicinity of the Kunlun and Altyn Tagh faults, far-field slip-rate associated with the faults and variation of rates along the length of the faults, surface displacement associated with the 1997 and 2001 earthquakes, possible linkage between these two events, influence of post-seismic processes on the strain accumulation in other sections of the fault. Slip rates are being compared with long-term rates inferred from geological observations.

利用雷达干涉测量技术，确定了北方阿尔金断裂系和昆仑断裂系沿着分布的现今应变率。这些断裂系统在亚洲大陆变形的动力学中起着关键作用，但它们的滑动速率和相关的变形仍然知之甚少。目前辩论的问题包括印度和亚洲之间的会聚量分别被地壳增厚和大陆块体的横向挤压所吸收，或整个大陆变形分布的特征。由于对碰撞区当今运动学知之甚少，这些问题尚未得到解决。此外，西藏北方是1997年和2001年两次大地震的发生地，在碰撞带的北方部分造成了目前地震间应变模式的中断，通过合成孔径雷达数据的干涉处理，正在绘制地面沿着活动断裂带视线位移的空间连续图。这项研究利用了欧洲航天局自1992年以来获得的覆盖西藏北方地区的ERS SAR数据的广泛存档。采用基线重新估计程序和数据平均法，按照加州雷达数据的方法，减少了由于轨道确定差和对流层相位传播延迟而引起的数据误差。然后结合视线位移图来约束1997年和2001年事件的长期断层蠕动以及同震滑动和震后松弛的变形过程模型。利用这些数据，研究了昆仑山和阿尔金断裂附近的震间应变分布、与断裂有关的远场滑动速率及其沿着断裂长度的变化、与1997年和2001年地震有关的地表位移、这两次地震之间的可能联系、震后过程对断裂其他部分应变积累的影响。滑动率正在与从地质观测中推断的长期速率进行比较。