【作者】 周德敏；

【导师】 甘卫军；

【作者基本信息】 中国地震局地质研究所 ， 固体地球物理学， 2013， 博士

【摘要】 自新生代以来，由于受印度板块对欧亚板块强烈碰撞和持续挤压的远程效应影响，天山造山带重新活动并再次隆升，成为欧亚大陆内部规模最大的再生造山带。GPS观测结果显示，跨天山（74°E～76°E）的现今地壳缩短速率约为20mm/a，几乎占印度板块与欧亚板块汇聚缩短总量的一半。据美国国家地震监测台网系统（ANSS）及新疆地震目录统计，自1889年以来，中西天山地区（70°～81°E）已发生Ms6.0级以上地震约百次。其中，Ms7.0～7.9级地震6次，Ms8.0级以上特大地震3次。类比2008年汶川Ms8.0地震所处青藏高原东缘强挤压、缓变形的地壳运动和区域构造背景，推测作为内陆典型的挤压构造活动带和地震多发带的中西天山地区在未来仍具有值得关注的大震潜势。自上世纪90年以来，以GPS为代表的空间对地观测技术的广泛应用，为我们以高精度、高效率、低成本和全天候方式获取各种规模尺度的地壳运动、构造形变及其动态演化过程提供了革命性的观测手段。到目前为止，国内外的许多研究机构已在中西天山地区开展了大量的GPS观测，并获得了高密度、高精度的地壳运动GPS速度场。此外，前人通过深地震宽角反射/折射剖面、流动地震台阵、深地震发射剖面及重磁联合反演等方法获得了中西天山地区岩石圈介质的分层结构。这些基础资料的积累为深入研究中西天山地区的现今地壳形变特征，探讨地壳形变、构造活动与地震潜势三者之间的相互关系，更加深刻地认知中西天山地区的运动学和动力学机制，特别是对柯坪-阿克苏地区的中-强地震危险性评估创造了重要条件。本论文具体开展了以下几方面的研究：一、中西天山地区多源GPS资料的收集、处理与融合中西天山地区的GPS地壳形变观测始于上世纪九十年代。其中，在中国境内的天山地区，由于“九五”国家重大科学工程“中国地壳运动观测网络”、“九五”国家重点科技攻关计划“伽师强震群及帕米尔东北侧现代构造运动和地形变的GPS监测研究”和“十一五”“中国大陆构造环境监测网络”等项目的支持，先后布设了88个GPS站点，并进行了多期观测；在境外中西天山地区，自1992年开始，由美国科学基金会资助，美国麻省理工学院（MIT）等数所大学与俄罗斯、吉尔吉斯斯坦、哈萨克斯坦等国家合作，先后布设了324个GPS站点，并开展了多期观测。由于无法获得境外天山324个GPS站点和境内南天山GPS监测网54个GPS站点完整的GPS原始观测资料，我们仅收集了两者分别在ITRF2005参考框架和稳定欧亚参考框架下的速度场。对于中国境内“中国地壳运动观测网络”和“中国大陆构造环境监测网络”34个GPS站点的原始观测资料，选用美国航空航天局（NASA）喷气推进实验室（JPL）的高精度GPS数据前处理软件GIPSY和后处理软件QOCA，采用先进的数据处理策略和严密的数据处理方法，获得这些站点的最新观测速度场。最后，对于境内外天山地区的两部分GPS速度场，以部分公共站点为“桥梁”，通过球面欧拉旋转变换，合理地融合在一起，获得了中西天山地区统一参考框架下高精度、高密度的GPS速度场数据，为本区域现今地壳运动的定量研究和地壳形变的构造运动学建模提供了至关重要的约束资料。二、中西天山地区现今地壳形变特征定量分析基于中西天山地区高精度、高密度的GPS速度场，定量分析了该区域现今地壳运动和构造变形特征，主要认识包括：（1）相对于稳定的欧亚板块，跨中西天山地区的北东向水平地壳运动速度从南天山的～20mm/a向北依次梯度变小至天山北侧的哈萨克地区～2mm/a，反映了中西天山在印度板块北东向俯冲、推挤作用下的强烈缩短隆升。（2）通过选取天山造山带整体固定框架，去除了天山造山带及其周围GPS站点的“刚性旋转”成分后，最大程度地突出了天山造山带内部不同区域的水平差异运动，结果显示：中西天山存在明显的挤出式“流滑”运动。其中，西侧顺着塔拉斯—费尔干纳断裂带流出，而东侧则沿北克明断裂向东运动；柯坪推覆体除南北向6～8mm/a的挤压缩短外，整体相对于天山造山带有明显的东向“流滑”运动，推测迈丹断裂有1～3mm/a的左旋错动；对于喀什凹陷与柯坪推覆体结合地区，南北向的挤压缩短量仅1～2mm/a；塔拉斯-费尔干纳断裂现今活动性有明显的分段特征，西北段有2～3mm/a的右旋滑动速率，中段没有明显的活动，东南段除3mm/a的右旋滑动外，还有一定的拉张分量；克明断裂（Chon-Kemin fault）、契里克断裂（Chilik fault）均有明显的左旋错动，滑动速率在2～3mm/a；（3）基于GPS速度场，计算、分析了中西天山地区的地壳应变率、剪切应变率，结果表明：整个天山造山带受到强烈挤压，帕米尔高原与天山交接区域的最大应变率值达到了221.2nanostrain/a。柯坪推覆体的三岔口、喀什凹陷北侧等局部区域存在一定的拉张；以皮羌断裂-伊塞克湖西为界，天山造山带东部的应变率值大于西部，在西部吉尔吉斯境内纳伦盆地等4个挤压盆地为低值区，应变率值小于20nanostrain/a；在造山带内部的那拉提断裂附近，存在应变率低值区“条带”；天山造山带北侧的盆山交接地带应变率值较小，除阿拉木图断裂东段末端与伊犁盆地交接地区应变率值较大（40nanostrain/a以上）外，吉尔吉斯山脉北缘等其他地区的应变率值小于20nanostrain/a；而在造山带南侧盆山交接地带，除喀什凹陷东段及柯坪推覆体柯坪地区的应变率值小于20nanostrain/a外，其余地区的应变率值大于40nanostrain/a。(4)基于GPS应变率场，计算得到与地震危险性直接相关的地震矩累积率。通过最大剪切应变率、地震矩累积率与地震分布的叠加分析发现，剪切应变率、地震矩累积率较大的地区，往往对应着地震活动相对频繁的区域；但在有些区域，尽管地壳形变比较强烈，但地震活动并不频繁，如纳伦盆地西部、柯坪推覆体三岔口东侧，这表明地壳形变的强弱与地震活动的频度之间存在较为复杂的关系。三、中西天山地区地壳形变特征的构造运动学模型解释以中西天山地区396个GPS站点的水平速度场和部分可靠程度较高的活动断裂的长期平均运动速率为约束，采用半无限弹性空间断裂位错模型，构建了中西天山地区地壳形变与断裂活动的构造运动学模型，反演获得了各主要活动断裂段闭锁层之下的长期运动速率。在此构造运动学模型的基础上，基于正演的连续计算，获取了整个区域连续分布的模型预测三维地壳运动场，并计算获得了模型预测的连续应变率场，取得了以下的主要认识：（1）中西天山地区的GPS地壳运动速度场能够用构造运动学的断裂位错模型进行较好的模拟解释。GPS站点位移速率的拟合残差大部分小于3mm/a，接近2～3mm/a平均观测精度。但在中西天山南北两侧的盆山交接地带，反演获得的逆冲断裂滑动速率与地质上的结果存在差异，主要与该区域逆冲断层基底滑脱面闭锁段底端深入天山内部有关。其中，天山北侧的断裂深入到伊塞克湖和苏萨梅亚盆地一带，而天山南侧的柯坪推覆体滑脱面闭锁段底端也并非沿着柯坪推覆体的前排断裂—柯坪塔格逆冲断裂的地表走向，而是深入到天山内部与迈丹-喀拉铁克断裂一致。（2）由于柯坪推覆体的各排逆冲褶皱带均有上陡下缓的“犁式”特点，采用简单的“断裂位错模型”无法对其地壳形变特征进行有效的解释。本文根据各排断裂的几何特征建立了“柯坪推覆体模型”，更好地吻合了GPS观测结果。对于部分未能很好拟合的GPS站点，可能的原因有如下几点：①采用的模型是对复杂断裂构造系统的一个简化，仅仅考虑了最前面的柯坪塔格逆冲褶皱带和依木干它乌逆冲褶皱带两条活动最强烈的断裂，其他几排逆冲褶皱带活动性相对较弱，而柯坪推覆体由4～6排逆冲褶皱断裂带组成，因而会造成后排断裂地区的GPS站点实测速度与拟合速度的偏差；②由于缺少足够的深部地球物理资料，无法准确判断深部基底卷入逆冲断裂的准确滑脱面埋深等信息；③由于野外地质工作的局限性，并不是所有断裂的所有断层都能获取可靠的断层参数。（3）基于构造运动学模型正演计算的现今地壳运动三维速度场，显示现今中西天山地区相对于塔里木盆地的隆升速率约为2.0±1.5mm/yr。考虑到天山的隆升历史及现今的实际隆升量，推测天山地区的挤压隆升很可能经历着由弱到强的递增演化过程，其强烈的长期平均剥蚀速率与GPS资料推算的长期平均隆升速率相当，约1.0mm/yr。四、柯坪-阿克苏地区的地震危险性分析针对“中国大陆7-8级地震危险性中长期预测研究”工作专项（简称M7工作专项）基于Ⅱ级活动块体边界带上的地震空区、GPS观测的地壳形变高梯度带等因素，在西南天山地区初步圈定了“柯坪-阿克苏地震重点监视区”。考虑到下地壳上地幔粘弹性松弛效应作用的长期性，采用黏弹性静态应力触发模型，计算了西南天山及周边地区过去近百年间（1898年～2012年）31个中-强震对柯坪-阿克苏地震重点监视区主要活动断层面上库仑应力的加/卸载状况，同时加入了由GPS资料所得到的长期构造运动加载下的应力积累。所得结果表明：柯坪塔格逆冲断裂西段与阿图什—八盘水磨逆冲构造的交接部位、迈丹断裂西段、喀拉铁克断裂西段及柯坪塔格逆冲断裂带三岔口段的库仑应力处于加载状态，预示着这些区域的地震危险性在增加（触发区）；柯坪塔格逆冲褶皱带的大山口—五间房段及附近的奥兹格尔他乌褶皱—逆冲带、乌什北逆冲断裂、南天山山前逆冲断裂及柯坪塔格逆冲褶皱带的一间房段的库仑应力处于卸载过程中，预示着这些区域的地震危险性在降低（抑制区）；皮羌山等柯坪推覆体内部多排逆冲褶皱断裂带、秋里塔格逆冲断裂带、古木别孜逆冲断裂带及柯坪塔格逆冲褶皱带柯坪岔口以北的阿依库勒段段的库仑应力积累量较小，预示着这些区域的地震危险性未受周边地震的显著影响（不确定区）。更多还原

【Abstract】 With the remote influence of the far field from intense collision and successiveextrusion of the India-Eurasian plate, the Tian Shan orgenic system has been activeand uplifting again since Cenozoic, then it becomes the largest orogenic system incentral Eurasia. Results of GPS observations, spanning from74°to76°, show that thecrust has been shortening with a rate of20mm/a, accounting for almost half of thetotal shortening rate between the India plate and the Eurasia plate. According to theNational Earthquake Monitoring Network System(ANSS) and Xinjiang earthquakecatalog, from1889to2012,50events,which is larger than Ms6.0,6events of Ms7.0~Ms7.9, and3events of Ms8have occurred in western and central Tian Shan (70°E~80°E). Similar to Earthquake Wenchuan Ms8of2008due to intense coillison, slowdeformation and local structural setting of Eastern Tibet, the western and central TianShan is a typical inland tectonic belt and earthquake-prone region and will get moreand more attention with great reason.Since the1990s, the GPS, which is an important technology of geodesy withhigh-accuracy, high-efficiency, low-expense and all-weather survey, provides arevolutionary method for measuring crustal movement, tectonic deformation of variedscales. Recently some research teams have made a lot of GPS measurements incentral and western Tian Shan. Besides，previous studies have probed the hierarchicalstructure of the Earth’s lithosphere by deep seismic wide-angle reflection/refractionprofiles，mobile seismic arrays，deep seismic reflection profiling，and inversions ofgravity and magnetic data. They are very important constraints data to makequantitative research about crustal deformation characteristics (such as shorteningdeformation distribution across the Tian Shan and tectonic changes) and seismichazard analysis. Focusing on these scientific issues，this thesis presents research workin five aspects as follows:1. Collection and processing of geodetic data in the western and central TianShan.GPS observations in western and central Tian Shan began in1992, and a numberof relevant projects provided a wealth of GPS data in this region afterwards. Thiswork has collected data of396stations in the western and central Tian Shan. Amongthem, the Chinese Tian Shan, funded by many scientific and technological projects,China Institute of Seismology and Earthquake Administration of Xinjian have madejoint efforts to carried out multi-period GPS observations, such as China Crustal Movement Observation Network, Continental Tectonics Environment MonitoringNetwork of China，the GPS observation project about the modern tectonic movementand crustal deformation of the Jiashi earthquakes and the movement of thenortheastern Pamir，which is96-913-07-03project of the Ninth-Five Year PlanNational Key Scientific and Technological Plans. In the northern Tian Shan(Kyrgyzstan/Kazakhstan)，funded by the National Science Foundation，MassachusettsInstitute of Technology (MIT) and several universities have made a lot of joint GPSobservations with Germany, Russia, Kyrgyzstan, and Kazakhstan since1992.As it is impossible to collect the original GPS data from324sites of the Tian Shanoutside China and54sites of South Tian Shan inside China, this thesis only uses theGPS velocity data under the ITRF2005framework and stable Eurasia framework.For data of34stations from China Crustal Movement Observation Network andChina Crustal Movement Observation Network, Continental Tectonics EnvironmentMonitoring Network of China, this work adopts the GPS data processing softwareGIPSY and post-processing software QOCA which were developed by NationalAeronautics and Space Administration (NASA) and Jet Propulsion Laboratory (JPL)to get the newly velocity of western Tian Shan, Finally using the common station asbridge, this work computes the Euler rotation parameter between them, then convertsthe velocity of Tian Shan to the frame of this work by adopting the Euler parameterand gets the dense, consistent and delicate velocity of Tian Shan, which providesimportant material for constructing the dynamic model for research of crustalmovement and tectonic deformation.2. Quantitative analysis for characteristics of present-day crustal deformation inthe western and central Tian Shan.Based on the high-accuracy and high-density GPS velocity field in the westernand central Tian Shan，this work analyzes quantitatively the features of crustal motionand tectonic deformation in this study region. The results are as follows:(1) Relative to stable Eurasia plate，the NE-directed horizontal movement velocityacross the western and central Tian Shan decreases from20mm/a in the southern TianShan to2mm/a in the northern Tian Shan (Kazakhstan), implying the Tian Shan isintensively shortening and uplifting.(2)Through the selection of the whole fixed framework of Tian Shan orgenicsystem，removing the “rigid rotation” of the Tian Shan orgenic system and itssurrounding GPS stations，the results further highlight the difference of the horizontal movement inside the Tian Shan orgenic system.An obvious extrusion-type “flow slide” movement exists in the mid-westernTian Shan. The west side of it flows along the Talas-Fergana fault zone，andeast side moves eastward along the northern Kemin fault zone.In addition to the6~8mm/a north-south extrusion shortening of the Kalpinthrust system，the whole has an obvious eastward “flow slip” relative to thethe Tian Shan orgenic system. This work also speculates that the Maidan faulthas a left-lateral slip of1~3mm/a. As to the combination of the Kashi sag andKalpin thrust system，the north-south extrusion shortening is only about1~2mm/a.The activity of Talas-fergana fault today has an obvious feature ofsegmentation. The northwest segment has2~3mm/a right-lateral slip rate，themiddle segment has no obvious movement，and the southeast segment notonly has3mm/a right-lateral slip rate but also has a large tensile component.Both the Chon-Kemin fault and Chilik fault have obvious left-lateral slip of2~3mm/a.(3) Based on the GPS velocity field，this thesis calculates and analyzes thecrustal strain rate and shear strain rate of the mid-western Tian Shan.The entire Tian Shan orgenic system was strongly squeezed. The max strainrate of the junction area of Pamir and Tian Shan is221.2nanostrain/a. There issome tension existing in the Kalpin thrust system，north part of Kashi sag andsome other places.Limited by the Piqiang fault-west Issyk lake，the strain rates of eastern TianShan orgenic system is higher than the western Tian Shan. To the west inKyrgyz, the Naryn basin and3other compressive basins are of low strainrates lower than20nanostrain/a. Inside the orogenic belt near the Natila fault，there is a low strain rate area called”strips”.The strain rates are relatively low in the basin-range transition north of theTian Shan orgenic system. In addition to the junction area between the end ofthe eastern Alamtu fault and Yili basin where the strain rates are relativelyhigh (more the40nanostrain)，the strain rates of the other areas in the northernKyrgyz Mountains are lower than20nanostrain/a. While in the transition zonebetween the basin and southern Tian Shan orgenic system, the strain rates aremore than40nanostrain/a，excluding the eastern Kashi sag and Kalpin thrustsystem where the strain rates are lower than20nanostrain/a. (4)Based on the GPS strain rate field，this work calculates the seismic momentaccumulation rate which is directly related to seismic risk. By the overlay analysis ofthe max shear strain rates，seismic moment accumulation rates and earthquakedistribution，it finds that the area with higher shear strain rates and earthquakemoment accumulation rates has relatively frequent seismic activity. However in someareas where the crustal deformation is relatively strong，the seismic activity is notfrequent like the western Naryn basin and the eastern Kalpin thrust system. Thisshows there is a relatively complex relationship between the strength of crustaldeformation and seismic activity.3. Tectonic kinematic model interpretation of crustal deformation of the westernand central Tian Shan.Restrained by the horizontal velocity field derived from data of the396GPSstations and the long-term average rates of movement of some active faults，using athree-dimensional deep-fault dislocation model，this work establishes an kinematicmodel of crustal deformation and active faults for the western and central Tian Shan,and inverts long-term slip rates of major faults. Then, based on this model andforward calculation, this thesis acquires the three-dimensional continuous distributionof crustal motion and the strain rate field for the whole region, which are statedbelow:(1) GPS crustal movement velocity field in the western Tian shan area can besimulated well by the fault dislocation model of tectonic kinematics. Most residuals ofthe GPS displacement rates are less than3mm/a，close to the average observationalaccuracy of2~3mm/a. In the basin-range transition zones on either side of themid-western Tian Shan，the thrusts slip rates derived from inversion are different fromthat from geological research. This is mainly because the locked sections of thebottom detachments of the thrust faults go down deeply into the Tian Shan. Amongthem，the northern Tian Shan fault goes deeply into the Issyk-Kul basin and SusaMyer basin. The bottom detachment latching segment of the Kalpin thrust system inthe southern Tian Shan does not run along with the front fault of Kalpin-Tage thrustsfault，instead goes down into the Tian Shan, in agreement with the Maidan-Kalatiefault.(2)Because each of thrust folds of the Kalpin thrust system has a listric feature,the crustal deformation cannot be simply explained by a simple three-dimensionaldeep-fault dislocation model. This work establishes a geometrical model for theKalpin thrust system based on the geometric characteristics of each of thrust fold zone. The inversion results using this model match largely with the GPS observations,except some stations. The reasons for these discrepancies are:①The model of thisthesis is a simplification to a complex fault system，in which only two fold thrustfaults have been taken into consideration. In the real Kalpin thrust system，the KalpinTage thrust fold and the Yimugantawu thrust fold belt are most intensive in activity,and the others are relatively weak. While the Kalpin thrust system is made up by4~6rows of fold thrusts，the velocity from GPS observations is different from the velocitycalculated by the model in the rear faults.②Due to lack of sufficient geophysical dataof deep structure，it is impossible to determine accurate depth of the deep detachmentsurface of basement-involved thrusts.③Because of the limitations of field geologicalwork, reliable data cannot cover all fault segments and all faults.(3) The forward calculation using the kinematic model yields thethree-dimensional velocity field of present-day crustal movement of the study area. Itappears that the uplifting rate of the western and central Tian Shan is about2.0±1.5mm/yr relative to the Tarim basin. Taking into account the uplift history and theuplifting amount, this work infers that the uplift in the western and central Tian Shanis progressive process from weak to intensive, in which the long-term denudation rateis close to the long-term uplift rate from GPS, which is about1.0mm/yr.4. Seismic hazard analysis of the Kalpin-Aksu regionAs to the project “long-term prediction of seismic hazard of Ms7.0~Ms8.0earthquake in China”, which is based on the seismic gaps in second-order active blockboundary belts and crustal deformation with high gradients by GPS observations，theKalpin-Aksu focused earthquake-monitoring area was preliminarily delimited in thesouthwestern Tian Shan. Taking the long-term viscoelastic relaxation effects of lowercrust and upper mantle into consideration，this work uses a viscoelastic static stresstriggering model to calculate the loading/unloading conditions of Coulomb stress onmain active faults of this focused area in the past nearly100years (1898~2012),during which31major earthquakes had happened in the southwestern Tian Shan andits surrounding areas. At the same time，stress accumulation under long term tectonicmovement loadings from the GPS observations are added. The results are as follows:Among the joints of the western segment of the Kalpintage reverse fault and theAtushi-Bapan Watermill reverse fault，the western part of Maidan fault，the westernpart of Kalatieke fault and the divergence of the Kalpintage reverse fault，theCoulomb failure stresses are in a loading state (triggering zone), implying a big seismic risk. At the Dakoushan-Wujianfang section of the Kalpintage reverse fold beltand the Aozigeertawu fold belt-reverse fault，northern part of the Wushi reverse fault，South Tian Shan range-front reverse fault and the Yijianfang section of the Kalpintagereverse-fold belt nearby，the Coulomb failure stresses are in an unloading state(inhibitory region), meaning low seismic hazards. On many rows of reverse-fold belts,such as Piqiangshan, in the Kalpin thrust system, as well as the Qiulitage andGumubiezi thrust faults, and the Ayikule section of the Kalpintage thrust fold zonenorth of the Kalpin fork, the cumulative Coulomb stresses are relatively smaller,indicating these areas are little affected by seismicity of surroundings (uncertainregion).更多还原