共查询到20条相似文献，搜索用时 421 毫秒
1.
利用最新的地球重力场模型,计算了新疆及邻近地区的自由空气重力异常、大地水准面扰动异常、地壳和上地幔平均密度异常以及地幔对流引起的岩石层底界面粘滞应力场分布．根据计算结果,对新疆天山地区的构造动力学特征进行了分析和推断,认为天山处于地幔对流形成的挤压沉降环境中,在南北不对称的挤压应力作用下快速隆升,挤压应力场中心在天山以南．这种应力场特征有利于塔里木板块向天山之下俯冲的观点．天山南北两侧的准噶尔盆地南缘和塔里木盆地北缘,是地壳内质量缺失区,是由于南北两侧地壳向天山下挤压而弯曲造成的．中国天山东段的深部密度分布特征与中段和西段的不同,可能是地幔对流分布的东西向差异造成的． 相似文献
2.
库尔勒—吉木萨尔剖面横跨塔里木盆地北缘、天山造山带和准噶尔盆地南缘.沿剖面完成了重磁联合反演,获得了岩石圈二维密度结构与二维磁性结构.结果发现,塔里木盆地与准噶尔盆地向天山造山带对冲.在地壳范围内,塔里木盆地北缘与准噶尔盆地南缘的平均密度较高,天山造山带的地壳平均密度较低.天山造山带具有较高的磁化强度,尤其表现在准噶尔盆地南缘至天山造山带中部的整个地壳范围内,预示着天山南北可能具有不同的构造演化历史、构造运动方式以及构造运动强度.在塔里木盆地与天山造山带以及准噶尔盆地与天山造山带的接触部位的上地幔顶部分别发现了低密度体,推测在塔里木盆地由南而北向天山造山带“层间插入与俯冲消减”,以及准噶尔盆地由北而南向天山造山带俯冲的过程中塔里木盆地北缘和准噶尔盆地南缘下地壳物质被带进天山造山带上地幔顶部.库尔勒—吉木萨尔剖面岩石圈二维密度结构与磁性结构为天山造山带的构造分段提供了岩石圈尺度的依据. 相似文献
3.
We use the Pg seismic phase along the Korla-Jimsar profile across the Tianshan orogen and the 3D finite difference method to inverse the velocity structure of the upper crust beneath the basement of this mountain. Based on the velocity structure, the Korla-Jimsar profile can be divided into three parts, i.e. the north edge of the Tarim basin, the Tianshan orogen, and the south margin of the Junggar basin. Within the Tianshan there is a pattern of four convexities and three concavities, which correspond to the southern Tianshan, the Yanqi basin, the middle Tianshan, the Turpan basin, and the Bogda Mountains. In the north edge of the Tarim basin, the basement is about 10km deep with small lateral variations of velocity. In the Tianshan the velocity varies greatly laterally. The basement depth of the Yanqi basin is 6 km, which becomes shallow rapidly northward, and almost to the surface at the middle Tianshan. South to Kumux there is a small intermountain basin, where the maximum basement depth is 3 km, and also turns very shallow near Kumux. The Luntai fault, which bounds the Tarim basin and Tianshan, has vertical dislocation of about 5 km. The Turpan basin is covered with so thick a sediment that its basement is 7 km deep. The boundary fault between the Tianshan and Turpan is the Bolohoro fault which is characterized by quick deepening basement and 7 km vertical dislocation. In the Junggar basin the basement is 8 km deep. On the Korla-Jimsar profile, the velocity distribution of the upper crust and the structure are featured by NS symmetry on both sides of the axis of the Middle Tianshan, consistent with the deep structure revealed by this profile. It means that the Tarim basin and the Junggar basin underthrust toward the Tianshan from south and north, respectively. Such a structural style is different from that of another profile, i.e. the Xayar-Burjing profile, suggesting that there may be an important tectonic boundary between these two profiles. 相似文献
4.
根据横跨中国境内天山的库车—奎屯宽频带流动地震台阵和区域地震台网记录的近震和远震P波走时数据，利用地震层析成像方法重建了沿该地震台阵剖面下方400 km深度范围内地壳上地幔的P波速度结构.结果表明：沿新疆库车—奎屯剖面，天山地壳具有明显的横向分块结构，且南、北天山地壳显示了较为强烈的横向变形特征，表明塔里木地块对天山地壳具有强烈的侧向挤压作用；在塔里木和准噶尔地块上地幔顶部有厚度约60～90 km的高速异常体，塔里木—南天山下方的高速异常体产生了较为明显的弯曲变形，而准噶尔—北天山下方的高速异常体向南一直俯冲到中天山南侧边界下方300 km的深度，两者形成了不对称对冲构造；在塔里木和准噶尔地块下方150～400 km深度存在上地幔低速体，其中塔里木地块一侧的上地幔低速物质上涌到南天山地块的下方；在塔里木—南天山200～300 km深度范围的上地幔存在高速异常体，它可能是地幔热物质向上迁移过程融断的塔里木岩石圈的拆离体. 上述结果表明，塔里木地块的俯冲可能涉及整个岩石圈深度，但其前缘仅限于南天山的北缘；青藏高原隆升的远程效应可能不但驱动塔里木岩石圈向北俯冲，同时还造成天山造山带南侧上地幔物质的涌入；天山造山带上地幔广泛存在的低速异常有助于其上地幔的变形，而上地幔物质的强烈非均匀性应有助于推动天山造山带上地幔小尺度地幔对流的形成；根据研究区地壳上地幔速度结构特征推断，新近纪以来天山快速隆升的主要力源来自青藏高原快速隆升的远程效应，相对软弱的上地幔为加速天山造山带的变形和隆升创造了必要条件. 相似文献
5.
In this study, from the travel time data recorded in the Tianshan passive seismic array experiment, we present the P-wave velocity structure of the upper mantle down to 660 km along the Kuqa-Kuitun pro-file in terms of seismic tomography technique. Based on the P-wave velocity model, we derive the corresponding 2D upper mantle density model. The 2D small-scale convection of the upper mantle underneath the Tianshan Mountains in China driven by the density anomalies is simulated using the hybrid finite element method combining with the marker-in-cell technique. The main features of the upper mantle convection and the reciprocation between the convection and mountain building are in-vestigated. The results manifest that (1) in the upper mantle underneath the Junggar basin and North Tianshan exists a counterclockwise convection, which scale is ~ 500 km; (2) underneath the Tarim ba-sin and South Tianshan exists a clockwise northward convection, which is relatively weak; (3) the convective velocity at the top of the upper mantle underneath the Tianshan Mountains in China should not be less than 20 mm/a, while considering the dependent of convective velocity on the viscosity; (4) the northward extrusion of the Tarim block plays a key role in the Cenozoic Tianshan mountain building and the present-day tectonic deformation of the Tianshan range is related closely to the upper mantle convection; and (5) the northward subduction of the Tarim block does not influence obviously the up-per mantle convection. 相似文献
6.
假设地震层析成像提供的地震波速异常对应于上地幔物质的密度异常分布，而该密度异常直接源于上地幔热对流相应的温度扰动. 在给定边界条件下，利用三维傅里叶变换，在波数域内求解控制流体行为的运动方程和连续性方程，得到上地幔小尺度对流流场. 利用密度异常驱动上地幔小尺度对流的数学 物理模型，采用胥颐、刘福田等提供的地震层析成像数据计算得到了我国西北及周边地区上地幔对流模式. 结果表明，对流流场的顶部在岩石圈较薄的盆地区域呈现上升发散流动特征，如塔里木盆地、柴达木盆地、哈萨克斯坦块体及准噶尔盆地；岩石圈较厚的山脉则对应了会聚下降的流动特征，如天山山脉、昆仑山山脉和祁连山山脉. 同时，塔里木盆地处于拉张状态，驱动其上地幔物质南下向青藏高原北部西昆仑运动，以及北上向天山下部流动，这可能是天山隆升的原因之一. 相似文献
7.
FOCAL MECHANISM SOLUTION AND TECTONIC STRESS FIELD CHARACTERISTICS OF THE MIDDLE TIANSHAN MOUNTAINS,XINJIANG 
下载免费PDF全文
下载免费PDF全文 ZHANG Zhi-bin ZHAO Xiao-cheng REN Lin 《地震地质》1979,42(3):595-611
The middle part of the Tianshan Mountains in Xinjiang is located in the north-central part of the Tianshan orogenic belt, between the rigid Tarim Basin and Junggar Basin. It is one of the regions with frequent deformation and strong earthquake activities. In this paper, 492 MS>2.5 earthquake events recorded by Xinjiang seismograph network from 2009 to 2018 were collected. The MS3.5 earthquake was taken as the boundary, the focal mechanism solutions of the earthquake events in this region were calculated by CAP method and FOCEMEC method respectively. At the same time the focal mechanism solutions of GCMT recorded historical earthquake events in this region were also collected. According to the global stress map classification standard, the moderate-strong earthquakes in the region are mainly dominated by thrust with a certain slip component, which are distributed near the combined belts of the Tarim Basin, Junggar Basin, Turpan Basin and Yili Basin with Tianshan Mountains. The thrust component decreases from south to north, while the strike-slip component increases. The spatial distribution characteristics of the tectonic stress field in the middle section of the Tianshan Mountains in Xinjiang are obtained by using the damped regional-scale stress field inversion method. The maximum principal compressive stress in axis the study area rotated in a fan shape from west to east, the NW direction in the western section gradually shifted to NE direction, its elevation angle is nearly horizontal, in the state of near horizontal compression. The minimum principal compressive stress axis is nearly EW, and the elevation angle is nearly vertical. Influenced by large fault zones such as Kashi River, Bolhinur, Nalati, Fukang, the southern margin of the Junggar and the north Beiluntai, the local regional stress field presents complex diversity. Under the influence of the northward extrusion of Pamir and Tarim blocks, the whole Tianshan is shortened by compression, but its shortening rate decreases from south to north and from west to east, the stress shape factor increases gradually from west to east, the intermediate principal compressive stress axis exhibits a change in compression to extension. There are some differences in the characteristics of tectonic stress field between the north and south of Tianshan Mountains. The regional maximum principal compressive stress axis is 15° north by east on the south side, while it is nearly NS on the north side. The deformation of the Tianshan Mountains and the two basins on both sides is obviously larger than that in the inside of the mountain. Changes in the crustal shortening rate caused by the rotation of the rigid Tarim block and Junggar block to the relatively soft Tianshan block, as well as the uplifts of Borokonu and Bogda Mountains, the comprehensive influence of the material westward expansion constitute the stress field distribution characteristics of the north and south sides of the middle section of Tianshan Mountains. The recent two MS6.6 earthquakes in the region caused the regional stress field to rotate counterclockwise. The post-earthquake stress field and the main source focal mechanism solution tend to be consistent. The seismic activity in the study area is week in the south and strong in the north. The focal depth is about 20km. Most strike-slip earthquakes occur near the junction belt of the Tianshan and Junggar Basin. 相似文献
8.
Introduction The northwest of China includes Tarim, Junggar and Qaidam basins, and Kunlun, Tianshan, Altun and Qilian mountains, as well as the north part of the Tibetan Plateau. For a long time, the study of lithosphere structures and dynamics in this area has been a popular topic in geoscience, and has yielded many results. For example, TANG (1994) and LI et al (1998) suppose that the tectonic structure of Tarim Basin is various with geological periods, which changes many times betwee… 相似文献
9.
10.
利用流动地震台阵记录的地震数据，通过地震层析技术反演了天山—帕米尔结合带的P波速度结构，揭示出地壳结构的非均匀特征及其与地震活动的对应关系. 分析结果表明，天山和西昆仑的双向挤压导致塔里木西部边缘地壳严重变形，在山前地区形成基底隆起带，地壳深部则被断裂分割成为若干块体，有的块体可能卷入造山带内部；喀什坳陷地壳深部结构相对完整，变形程度较弱；天山和西昆仑的地壳结构显示出缩短增厚的波速特性，在与塔里木接壤的局部地区，壳幔边界附近存在热物质的侵入迹象. 大部分地震都发生在塔里木西部边缘的壳内高速块体周围，推测块体之间的相互作用和应力调整是导致天山—帕米尔结合带频繁发生地震的主要原因，伽师地震则与构造变形由天山向塔里木内部扩展以及该地区的地壳非均匀结构有关. 相似文献
11.
南天山及塔里木北缘构造带位于帕米尔地区东北侧,地震活动强烈。文中通过地质构造剖面、深部探测资料和地震震源机制解资料,综合研究了该区的地震构造模型。结果认为,该区的构造活动主要表现为天山地块逆冲于塔里木地块之上。天山构造系统包括迈丹断裂及其前缘推覆构造;塔里木构造系统包括深部的塔里木北缘断裂、基底共轭断层和浅部的推覆构造。塔里木北缘断裂是发育于塔里木地壳内部的高角度断裂,其形成原因在于塔里木和天山构造变形方向的差异。塔里木北缘断裂为研究区大地震的主要发震构造,天山推覆构造和塔里木基底断裂系统均具有不同性质的中强地震发震能力 相似文献
12.
The Central Asian Orogenic Belt (CAOB) represents the world's largest Phanerozoic accretionary orogen, the major phase of which was built during the closure of the Paleo-Asian Ocean. The Tianshan orogenic belt forms the southwestern segment of the CAOB and has been the focus of investigations related to the evolution of the CAOB. Here we present results from an analysis of the crustal structure and upper mantle discontinuity beneath the Chinese Tianshan by employing H-k stacking technique as well as depth domain and synthetic receiver functions. Our results identify a double peak of Moho Ps in the Tianshan orogenic belt, suggesting the possibility of insertion of the lower crust of the Tarim Basin into this belt, with the latter retaining its initial crustal architecture. Our results provide insights into the dynamics of northward extrusion and the N–S trending crustal shortening of the Tianshan orogen during the convergence of the India and Eurasia blocks. 相似文献
13.
《Earth and Planetary Science Letters》2006,241(3-4):804-814
We present new seismic refraction/wide-angle-reflection data across the Altyn Tagh Range and its adjacent basins. We find that the crustal velocity structure, and by inference, the composition of the crust changes abruptly beneath the Cherchen fault, i.e., ∼100 km north of the northern margin of the Tibetan plateau. North of the Cherchen fault, beneath the Tarim basin, a platform-type crust is evident. In contrast, south the Cherchen fault the crust is characterized by a missing high-velocity lower-crustal layer. Our seismic model indicates that the high topography (∼3 km) of the Altyn Tagh Range is supported by a wedge-shaped region with a seismic velocity of 7.6–7.8 km/s that we interpret as a zone of crust–mantle mix. We infer that the Altyn Tagh Range formed by crustal-scale strike-slip motion along the North Altyn Tagh fault and northeast–southwest contraction over the range. The contraction is accommodated by (1) crustal thickening via upper-crustal thrusting and lower-crustal flow (i.e., creep), and (2) slip-parallel (SW-directed) underthrusting of only the lower crust and mantle of the eastern Tarim basin beneath the Altyn Tagh Range. 相似文献
14.
小波变换在地震宽角反折射资料处理中的应用 总被引：8，自引：1，他引：7
小波分析方法用于地震宽角反折射资料处理 ,它可将地震信号的分辨率由传统的1 /2- 1 /4λ（波长 ）提高到优于 1 /6λ .利用小波分析方法对沙雅-布尔津地震宽角反折射剖面资料进行处理 ,发现天山造山带的壳幔过渡带由 7- 8个高低速相间的薄层构成 ,平均速度较低 ,总厚度约 2 0km .而塔里木盆地北缘与准噶尔盆地的壳幔过渡带不具有这一特点 ,壳幔间主要以一级间断面实现过渡 .天山造山带与准噶尔盆地壳幔过渡带详细结构及其二者之间的差异特征为天山造山带地球动力学“层间插入消减模型”的建立提供了重要依据 相似文献
15.
西南天山-塔里木盆地结合带浅深构造关系 ——深地震反射剖面的初步揭露 总被引：4，自引：0，他引：4
盆山结合部的浅-深结构样式是进行陆内造山动力学研究与讨论的重要依据.2007年,在喀什东的天山与塔里木盆地之间的过渡带上,完成了一条近南北向的长度为121 km的主动源深地震反射剖面,显示出盆山结合部现今地壳尺度的构造格架.剖面南部呈现出10~12 km巨厚的沉积盖层,沉积盖层内发育滑脱断层;盆山结合部多排隆起构造以及天山山前上地壳显现出向北倾斜的断裂与地表地质观察吻合;盆山结合带展现出滑脱与逆冲推覆构造相关的断层褶皱;与塔里木盆地稳定沉积层相比,在南天山浅、中层地层受到强烈的变形改造,导致地层比较破碎,反射变弱、连续性较差;时间剖面上可以追踪到比较连续的Moho反射,从南向北有加深的趋势.深地震反射剖面揭露出的西南天山与塔里木盆地的这些浅-深构造,展现出塔里木盆地盖层向南天山滑脱与南天山向塔里木盆地逆冲推覆的特征,反映出陆内汇聚下的盆山耦合关系. 相似文献
16.
利用横跨塔里木盆地、阿尔金造山带和柴达木盆地的拜城—大柴旦综合地球物理剖面的人工地震宽角反射/折射资料，对拜城—大柴旦剖面研究区上地壳的Q值结构进行了反演. 结果表明，研究区上地壳的Q值结构具有明显的分层性，Q值随深度的加大而增大；横向对应的不同地质构造单元的Q值具有不同的分布特点. 塔里木盆地的上地壳具有稳定的Q值结构，但盆地北缘（特别是库车坳陷）的Q值比南缘的低，表明北缘的介质比较破碎. 这可能与盆地北缘活跃的构造特征与巨大的沉积厚度有关，是引起盆地南北两侧地震活动性差异（北缘强，南缘弱）的重要原因之一. 阿尔金造山带上地壳的平均Q值较高（约500），这可能由于结晶基底埋藏较浅，基岩出露，因此地震波在此处传播能量衰减较慢所致. 柴达木盆地西半部分上地壳的Q值除了表层的（厚1.0～2.0km）较高外，其余各层的Q值与塔里木盆地中部的相当（平均约400），显示了与塔里木盆地相似的稳定构造. 相似文献
17.
中国西部三维速度结构及其各向异性 总被引：24，自引：5，他引：24
本文用覆盖中国的358条勒夫面波路径资料,研究了10.45-113.80s范围内中国西部的三维SH波速度结构.结果表明,各构造单元的SH波速度结构均有明显的差别.作为稳定块体的塔里木盆地,壳内重力分异程度较高,上、中、下地壳厚度差别小,壳内无明显的低速层,地壳平均速度比较小;上地幔低速层埋深大且层中速度大;区内横向变化小.构造活动区如天山、青藏高原,其突出的特征是下地壳厚度大且速度大,上地幔盖层速度值相当高.这与西伯利亚、印支板块的挤压有密切的关系.青藏高原东部及其北、东边缘地区壳内存在低速层,上地幔低速层埋深浅,一些地区存在壳幔过渡层.面波各向异性研究表明,青藏高原、天山及印支板块北缘下存在明显的各向异性,以构造边缘地区及上地幔低速层附近最为突出.印度板块、西伯利亚板块与中国大陆间的碰撞引起强大的水平压力和一定的下插作用,是造成青藏高原隆起、地壳增厚、天山隆起的最根本的因素,同时也促成壳幔中辉石、橄榄石的定向排列和物质运移,因而出现明显的各向异性现象. 相似文献
18.
以深部地球物理资料为基础,介绍了天山地震带上地幔的基本结构,讨论了天山不同地区上地幔介质的动力学性质和可能的驱动机制。认为水平挤压形变是造成西天山和天山毗邻西昆仑附近区域上地幔岩石圈缩短和增厚的主要原因;而在中天山和东天山靠近准噶尔盆地南缘一带,除了板块运动造成的水平挤压力之外,上地幔热物质有可能上浮甚至侵入到地壳之中。它们与水平运动一样,对壳内脆性介质的构造活动起到非常重要的作用,特别是地壳底部莫霍面附近的低速滑脱层成为震源区深部构造的一个明显标志。此外,自从印度 亚洲大陆碰撞以来,天山部分地区固结冷却的山根有可能在多重挤压变形和小尺度热对流的共同作用下,脱离它们的原有的层位而沉入上地幔 相似文献
19.
大量的地质和地球物理资料表明 ,年轻的大陆构造活动区的下地壳可能因热软化而出现透入性非地震式顺层韧性流动 ,这种下地壳层流作用驱动大陆上地壳发生地震式脆性断块运动 ,形成盆山格局 ,发生圈层耦合。大陆下地壳低粘度物质顺层流动可能是在地幔岩浆底侵作用为下地壳提供热能和添加幔源物质的基础上 ,并在地幔上升派生的重力和剪切力作用下 ,造成大陆下地壳热软化物质从盆地下部的幔隆区顺层流向相邻造山带之下的幔拗区。在下地壳层流过程中 ,地温场和速度场发生变 相似文献
20.
Tian Qinjian 《中国地震研究》2007,21(1):74-84
The interaction zone between southern Tianshan and northern Tarim is located at the northeast side of Pamir. It is a region with high seismicity. We constructed a seismotectonic model for the west part of this zone from geological profiles, deep crust seismic detection and earthquake focal mechanisms data. Based on the synthesized geological features, deep crust structure, and earthquake focal mechanisms, we think that the main regional tectonic feature is that the Tianshan tecto-lithostratigraphic unit overthrusts on the Tarim block. The Tianshan tectonic system includes the Maidan fault and thrust sheets in front of the fault; The Tarim tectonic system includes the underground northern Tarim margin fault, conjugate faults in basement and overthrust fault in shallow. The northern Tarim margin fault is a high angle fault deep in the Tarim crust, adjusting different trending deformation between Tianshan and Tarim. It is a major active fault that can generate large earthquakes. The other faults, such as the Tianshan overthrust system and the Tarim basement faults in this area may generate moderately strong earthquakes with different styles. 相似文献