中亚塔拉斯-费尔干纳断裂现今的走滑速率及其分段变化特征——基于GPS观测的深究  

PRESENT-DAY STRIKE-SLIP RATE AND ITS SEGMENTAL VARIATION OF THE TALAS-FERGHANA FAULT IN CENTRAL ASIA:INSIGHT FROM GPS GEODETIC OBSERVATIONS

作　　者：代成龙 张玲[1] 梁诗明[1] 张克亮[1] 熊小慧[1] 甘卫军[1] DAI Cheng-long;ZHANG Ling;LIANG Shi-ming;ZHANG Ke-liang;XIONG Xiao-hui;GAN Wei-jun(State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration,Xinjiang Pamir Intracontinental Subduction National Field Observation and Research Station,Beijing 100029,China)

机构地区：[1]中国地震局地质研究所,地震动力学国家重点实验室,新疆帕米尔陆内俯冲国家野外科学观测研究站,北京100029

出　　处：《地震地质》2021年第2期263-279,共17页Seismology and Geology

基　　金：中国地震局地质研究所基本科研业务专项(IGCEA2001)资助。

摘　　要：塔拉斯-费尔干纳断裂沿NW向斜切西天山山脉,以愈千km的规模尺度构成了中亚地区重要的区域构造边界带。早年和近期的许多地质研究结果均显示该断裂具有强烈的活动性,所估计的全新世滑动速率高达8~20mm/a,但GPS大地测量的简略估算结果却表明其现今整体的滑动速率仅约为2mm/a甚至更低。文中基于塔拉斯-费尔干纳断裂周边大范围的最新GPS速度场资料,通过断裂两侧远、近场地壳的差异运动分析、断裂沿线最大剪切应变率定量类比,以及借助半无限弹性空间三维断裂位错模型的严密反演,证实了该断裂现今仅具有中等偏弱的活动强度:塔拉斯-费尔干纳断裂存在分段活动性,其西北段、中段、东南段的右旋走滑速率分别为(2.1±0.7)mm/a、(3.3±0.4)mm/a和(2.4±0.7)mm/a,即中段的速率略大于西北段和东南段,但量值均不突出,远低于目前大多数地质结果所估计的高速率。同时,根据区域无自旋参考框架下断裂两侧远、近场GPS速度矢量的差异甚微的特征,认为塔拉斯-费尔干纳断裂现今的低滑动速率并非断裂强闭锁的暂态表现。The Talas-Fergana Fault(TFF)with a total length of more than 1-000km is a large dextral strike-slip fault across the West Tianshan Mountains in the northwest direction.The fault plays an important role in accommodating deformation in Central Asia and has attracted much attention by geologists due to the huge controversy in its strike-slip rate and kinematic pattern.Previous studies indicated that its average dextral strike-slip rate is 8~20mm/a since Late Holocene based on offset ephemeral stream valleys and 14 C dating method.Some researchers recently updated the strike-slip to 2.2~6.3mm/a by the application of multiple dating methods(10 Be,26 Al,36 Cl,luminescence,and radiocarbon)and satellite images with higher precision.But the strike-slip rates derived from modern GPS velocity field are only~2mm/a or even as low as 0.8mm/a.Thus,there is a substantial divergence between geological results and geodetic results in the strike-slip rate of the TFF.Some scholars believe that the huge difference between the geological rate and the rate obtained by geodetic measurements is caused by fault locking.In this study,the updated GPS data was used to establish velocity field of the West Tianshan Mountains relative to the stable Eurasian framework and the velocity field without self-rotation.The velocity field shows that the Tianshan Mountains are under intense crustal shortening and deformation.Moreover,for the TFF,as an important boundary fault in the western Tianshan Mountains,whether the far velocity field or the near velocity field,the differential movement of the crust is not obvious.And far-field velocity vectors away from the TFF show that there is minor difference of crustal movement along the fault.The TFF does not have the typical characteristic of locked fault that there is a big difference in velocities of far-field vectors,but a small difference in that of near/mid-field vectors.Thus,the activity of the fault is weak actually.To further illustrate the overall low slip rate of the TFF,we compare the maximum shea

关 键 词：塔拉斯-费尔干纳断裂 西天山 GPS速度场 运动速率 断层分段 

分 类 号：P315.2[天文地球—地震学]