【作者】 吴富峣；

【导师】 李海兵；

【作者基本信息】 中国地质科学院 ， 构造地质学， 2011， 硕士

【摘要】 新生代以来,印度板块与欧亚板块碰撞的远程效应使得青藏高原及周边地区多条深大断裂复活,如阿尔金断裂、鲜水河断裂、塔拉斯费尔干纳断裂等,这些新生代复活断裂控制了周边地区的地质形成演化。帕米尔-西昆仑山、青海玉树地区就位于这些断裂附近,是青藏高原的重要组成部分,这些地区的构造变形强烈,构造样式丰富,活动构造大量分布,地震频发,记录了青藏高原新生代变形隆升重要地质信息。本文选择两个区域作为研究区,对西昆仑山前褶皱冲断带进行晚新生代构造变形研究,对青海玉树地区进行2010年地震变形作用研究,探讨青藏高原西北缘造山机制和2010年玉树地震对高原隆升的意义。首先通过对西昆仑山前冲断带的卫星影像解译、DEM数据处理、河流阶地分析和地球物理剖面解释,结合野外地质、地貌的观察与测量,对研究区的构造地貌和构造变形进行了定性和定量的研究。取得如下认识：(1)区域构造地貌研究表明帕米尔-西昆仑构造带与塔里木盆地之间为强烈的地形陡变带,高程剖面显示高程垂向上变化大,显示构造造山作用强烈。从区域高程分布推测帕米尔高原前缘与西昆仑山造山机制有所不同,前者由山脉隆升和断裂右旋作用同时造山,后者主要是构造抬升。区域内主夷平面在3600-5200m的高度发育。坡度分析表明区域上的坡角以中陡坡和陡坡为主,悬崖峭壁发育,地形强烈的起伏,构造活动性大。在山前冲断带及其前陆盆地内部,坡度休止角约为15°,在高原内部基岩裸露区,坡度休止角约为330。区域内水系的分布具有以下几个特征：水系总的呈丁字型或L型,显示河流被断裂错开,河流袭夺发育；冲断带内河流东侧支流水系多于西侧,可能暗示东侧翘起幅度较高。面积高程曲线积分显示研究区处于地貌发育幼年期,山体还在继续抬升。(2)河流阶地研究表明克里雅河与策勒河阶地均为构造成因,详细研究表明克里雅河第四纪以来的平均下切速率为0.15mm/a,自30.86ka以来的平均下切速率为0.76mm/a,自12.44ka以来的平均下切速率为1.34mm/a,表明第四纪以来研究区河流加速下切,西昆仑山山地隆升存在明显的加速过程。(3)英吉沙背斜褶皱向东倾伏,说明其生长不仅仅只受腹陆逆冲推覆控制,同时受到艾古斯背斜向东生长变形前缘的影响。英吉沙背斜的生长控制了区域上水系的分布,地貌上主要表现为河流在背斜南翼沿背斜走向向东流动。通过对英吉沙背斜野外调查、地表DEM剖面和地球物理剖面的分析,认定英吉沙背斜为一滑脱褶皱。在地球物理剖面上识别出英吉沙背斜发育Q1生长地层。通过多余面积法计算得出英吉沙背斜隆升以来缩短量约为720 m,以英吉沙背斜附近的磁性地层年龄1Ma做为Q1年龄,计算得出缩短速率约为0.72 mm/a。同时本文对2010年4月14日青海玉树Ms7.1级地震变形作用进行了研究.野外调查表明玉树地震同震地表破裂带长约65km,破裂带走向为310°,破裂面向NE陡倾,地表破裂带由两部分组成,其中西侧部分长约19km,东侧部分长约30km,两者之间存在约15km的无破裂区。玉树地震同震地表破裂以右阶雁行状破裂分布为主要特征,呈现左旋走滑性质,伴随有垂直位移。统计显示同震地表破裂垂直位移(dV)与水平位移(dh)的比值在0.13～0.53之间,地貌累积dV与累积dh比值为0.27-0.63。同震dv/dh与地貌dv/dh的相似显示玉树南山的形成和玉树地震具有同样的运动学和动力学性质,玉树南山的形成是地质历史上沿玉树断裂多次类似于玉树地震的地震活动的结果,计算出需要1800～2600次地震才能造成玉树南山的隆升。前人研究本段断层地震复发周期为120～200年,计算出断层开始活动时间不晚于20万～40万年以前。更多还原

【Abstract】 Far field effect of collision between Indian plate and Euro-Asia plate since Cenozoic era reactivates some deep and huge faults around Qinghai-Tibet plateau and its margins, such as Alyth fault, Xianshuihe fault, Talas Fergana fault, et al. These faults control the geological evolution of margin area of Qinghai-Tibet plateau. Be important parts of plateau, Pamir-West Kunlun mountain and Yushu distribute around these faults. These area features with strong tectonic deformation, a sundry of structural styles, a lot of active tectonics and frequent earthquakes, having recorded the critical geological information in the process of Cenozoic plateau uplift. This dissertation heads to study on the late Cenozoic deformation of thrust-belt of West Kunlun mountain and do some analysis for coseismic deformation of 2010 Qinghai Yushu earthquake, looking forwars to exploring the uplift mechanism in northwestern plateau and the contribution of 2010 Yushu earthquake to plateau uplift.At first, based on the interpretation of satellite images, processing of DEM data, analysis of river terraces, interpretation of geophysical profiles, as well as field morphotectonic and geological investigations and observations, a qualitative and quantitative morphotectonic and deformed features of thrust-belt of West Kunlun moutain was investigated. Some cognition are got:Spatial geomorphology analyses find that a very abrupt landform zone distributed between Pamier-West Kunlun tectonic zone and Tarim Basin. Swath DEM profiles across this zone suggest huge vertical elevation change, indicating strong structural activity. Different mean elevation plane suggests the Pamir Plateau has an uplifting mechanism of thrusting with a right lateral component which is different from West Kunlun mountain’s nearly pure thrusting. Main planation surfaces appear at 3600-5200 meters high. Slope analyses find that slope angle is rather abrupt and big roughness suggests a strong tectonic activity. Also slope analyses suggest that the slope angle is ca.15°in the basin and ca.33°in the inner plateau. Rivers tend to be offset by fault, making local drainage pattern become L-like. Tributaries tend to occurred on the east side of the river, suggesting east basin’s warping. Hyposometric curve indicates study area is in the geomorphic infancy phase and the mountain is still uplifting.River geomorphic study finds that Keliya he terraces and Cele he terraces are tectonic terraces, which can arguably reflect mountain uplifting. Keliya he terraces research suggest Keliya he River has a Quaternary mean incision rate of 0.15mm/a, a mean incision rate of 0.76mm/a since 30.86ka,1.34mm/a since 12.44ka, these datum reflect an accelerated uplift past of West Kunlun mountain.Yingjisha anticline plunges east, this pheonomenoum only makes sense in the case of Yingjisha anticline’s growth ont only controlled by main thrust fault in hinterland but also influenced by Aigusi anticline’s lateral-propagation. Yingjisha growth anticline decided the drainage pattern, making river flow along its strike on the south flank of it. Field investigation, as well as analyses about DEM and geophysical profiles across Yingjisha anticline, finds Yingjisha anticline is a detachment anticline, identifying Q1 growth fold developed on the flank of anticline from geophysical profiles. Fit with excess area model we find Yingjisha anticline has a shortening magnitude of ca.722km and a mean shorten rate of ca.0.72mm/a since 1Ma.At the same time, this dissertation also focus on the coseismic deformation of Qinghai Yushu earthquake(Ms7.1) attacked on April 14,2010. Field investigation found that Qinghai Yushu Ms7.1 Earthquake produced a～65 km long co-seismic surface rupture zone which strikes 310°and dips NE. The entire zone is composed of two parts:the western section is about 19 km-long and the eastern section 30 km. Between these two sections, a 15 km-long zone surface rupture gap is observed. Surface ruptures display common sinistral lines mainly featuring right stepping en-echelon ruptures, while vertical offsets developed. The ratio between co-seismic vertical offset (dv) and horizontal offset (dh) ranges from 0.13 to 0.53, while the geomorphic dv/dh rate of 0.27～0.63 is close to co-seismic dv/dh (0.13～0.53), indicating that the Yushu NanShan uplift probably shows the same kinematic and dynamic characteristics. In other words, the Yushu Nan Shan uplift is resulting from the cumulative vertical offsets produced by many earthquakes similar to Yushu earthquake along Yushu fault in the geological history. We conclude that we need 1800-2600 earthquakes similar to Yushu earthquake to form Yushu Nan Shan. Former research reckon the recurrence period of the Yushu section of Ganzi-Yushu fault zone to be 120-200 years, which would then make us believe that this fault section’s activity started 200-400 ka ago.更多还原