| 帕米尔东北部木吉断层晚第四纪运动性质和滑动速率的约束 |
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| 引用本文： | 邓金花,韩非,李涛,张博譞,许建红,姚远.帕米尔东北部木吉断层晚第四纪运动性质和滑动速率的约束[J].第四纪研究,2020(1):114-123. |
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| 作者姓名： | 邓金花 韩非 李涛 张博譞 许建红 姚远 |
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| 作者单位： | 中国地震局地质研究所;云南大学地球系统科学研究中心;中山大学地球科学与工程学院;中国地震局第二监测中心;新疆维吾尔自治区地震局 |
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| 基金项目： | 国家自然科学基金项目(批准号:41772196);中国地震局地质研究所地震动力学国家重点实验室自主课题项目(批准号:LED2014A05)资助。 |
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| 摘 要： | 帕米尔造山带是印度-欧亚大陆会聚带的西构造结。木吉断层作为中-西帕米尔与东帕米尔的最北部边界转换断层,其运动性质和滑动速率的准确限定对于理解帕米尔现今应力状态和运动学特征等具有重要意义。本文以木吉断层东段布拉克村北位错特征显著的冰碛台地(39.2020°N,74.3910°E)为研究对象,基于高分辨率卫星影像解译、野外地质地貌调查、差分GPS测量和冰川漂砾宇宙成因核素10Be暴露测年,获得布拉克北冰碛台地形成(16.8±3.5 ka)以来木吉断层的累积右旋位错量、垂直位错量、南北向拉张量以及最小速率分别为约190 m、105±12 m、34±12 m和11.3±2.4 mm/a、6.3±1.5 mm/a、2.0±0.8 mm/a;三者的比值约为6:3:1,水平向的总滑动速率为11.5±2.3 mm/a。与位于断层中部近乎纯走滑的阿克萨依处相比,木吉断层在布拉克北以右旋走滑为主的同时,具有明显的正断分量。断层在布拉克北的水平向总滑动速率11.5±2.3 mm/a与阿克萨依处右旋走滑速率的最大值(9.4±0.9 mm/a)大致相当;因此尽管断层沿走向的运动性质发生了显著变化,其水平向滑动速率大致保持恒定。
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| 关 键 词： | 帕米尔 公格尔拉张系 木吉断层 冰碛堤 滑动速率 宇宙成因核素测年 |
LATE-QUATERNARY SLIP SENSE AND RATE OF THE MUJI FA U LT,NORTHEASTERN PAMIR |
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| Deng Jinhua,Han Fei,Li Tao,Zhang Boxuan,Xu Jianhong,Yao Yuan.LATE-QUATERNARY SLIP SENSE AND RATE OF THE MUJI FA U LT,NORTHEASTERN PAMIR[J].Quaternary Sciences,2020(1):114-123. |
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| Authors: | Deng Jinhua Han Fei Li Tao Zhang Boxuan Xu Jianhong Yao Yuan |
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| Institution: | (State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration,Beijing 100029;Research Center for Earth System Science,Yunnan Key Laboratory of Earth System Science,Yunnan University,Kunming 650500,Yunnan;Guangdong Provincial Key Laboratory of Geodynamics and Geohazards,School of Earth Sciences and Engineering,Sun Yat-sen University,Guangzhou 510275,Guangdong;The Second Monitoring and Application Center,China Earthquake Administration,Xi'an 710054,Shaanxi;Seismological Bureau of the Xinjiang Uygur Autonomous Region,Vrümqi 830011,Xinjiang) |
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| Abstract: | The Pamir orogen lies at the northwestern syntaxis of the India-Asia convergence zone.Active tectonic investigations,geodetic GPS measurements and focal mechanisms of major earthquakes all indicate that modern deformation of the Pamir is characterized by strong crustal shortening along its northern and western margins as well as significant crustal extension along the Kongur Extensional System,which divides the central-western Pamir from the eastern Pamir.The SEE-trending Muji Fault is the northernmost segment of the Kongur Extensional System and acts as the northern boundary fault between the central-western and the eastern Pamir.Well determinations of the slip sense and slip rate of the fault are critical for our understanding the current stress status and kinematic process of the Pamir.This study focuses on the displaced moraine deposits at north Bulake(39.2020°N,74.3910°E),eastern segment of the Muji Fault.Based on high-resolution satellite image interpretation,detailed field observations and differential GPS topographic measurement of the moraine deposits,the dextral displacement,vertical displacement and north-south extension of the fault are well determined to be ca.190 m,105±12 m and 34±12 m,respectively;the age of the moraine deposits is determined to be 16.8±3.5 ka by cosmogenic nuclide 10Be exposure dating of seven granite boulders on the surface.These yield a dextral-slip rate,vertical-slip rate and north-south extension rate of 11.3±2.4 mm/a,6.3±1.5 mm/a and 2.0±0.8 mm/a,respectively.The ratio of the dextral-slip rate,vertical slip rate and north-south extension rate is around 6:3:1 and the horizontal slip rate is 11.5±2.3 mm/a.Compared to the central segment of the fault at Aksayi,where the fault is characterized by mostly dextral slip,the fault at north Bulake(eastern segment)is characterized by dextral slip with significant normal-faulting component.Because the horizontal slip rate of 11.5±2.3 mm/a at north Bulake is broadly consistent with the maximum dextral slip rate of 9.4±0.9 mm/a at Akesayi,the slip rate maintains roughly constant along the fault in spite of significant change of its slip sense.Our result can make two conclusions:(1)Although the Muji Fault has significant different strike(SEE-trending)and slip sense(dextral slip)from the rest segment of the Kongur Extensional System(SSE-trending and normal-faulting,respectively),both of the fault segments indicate that the central-western Pamir is separating from the eastern Pamir;(2)The extension rate of 1.4°~2.0°/Ma between the central-western and eastern Pamir,which is estimated from slip rate at Aksayi,can be used to represent the modern extension rate of the Pamir interior. |
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| Keywords: | Pamir Kongur Extensional System Muji Fault moraine slip rate cosmogenic nuclide dating |
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