The Vertical Deformation and Horizontal Displacement Fields,Movement, and Seismicity of the Island Arc Tectonics

In this work,the vertical deformation,horizontal displacement,and stress fields of arcuate tectonics are theoretically derived from the horizontal tectonic stress; then the characteristics of tectonic movement,seismicity,and focal mechanism of arcuate tectonics of the entire world are explained.It is pointed out that the island arc and other arcuate tectonics are gradually developed under the displacement and stress fields of the arcuate tectonics and that the under-thrusting action of the ocean plate is secondary.The distance formulas between the volcanic arc and the trench are suggested and also that theoretical results are consistent with actual data.

New insights of the Cenozoic Rotational Deformation of Crustal Blocks on the Southeastern Margin of the Tibetan Plateau and its Tectonic Implications

Objective The lateral extrusion of southeastern edge of the crustal materials around the Tibetan Plateau since the Oligocene is believed to be one of the main inducements of-1300 km latitudinal crustal convergence in the Tibetan Plateau, since the collision of India and Eurasia in the Paleogene. Two end-member models were used to describe the process of lateral extrusion of crustal material on the southeastern edge of the Tibetan Plateau. The ＂tectonic escape＂ model suggests the Indochina Block, Chuandian Fragment and Shan-Thai Block have experienced lateral extrusion along strike-slip fault systems, and the ＂crustal flow＂ model suggests that the upper crust has undergone southeastward escape in the form of ductile deformation, driven by viscous lower crustal flow channels. In addition, the GPS observations surrounding the Tibetan Plateau indicate that crustal materials currently experience clockwise rotation around the Eastern Himalaya syntaxis. This work conducted paleomagnetic studies in the Cretaceous and Paleogene red-beds along the southeastern margin of Tibetan Plateau,

Earthquake-induced Soft-sediment Deformation Structures in the Dengfeng Area,Henan Province,China:Constraints on Qinling Tectonic Evolution during the Early Cambrian

Soft-sediment deformation structures are abundant in the Cambrian Zhushadong and Mantou formations of the Dengfeng area, Henan Province, China. Soft-sediment deformation structures of the Zhushadong Formation consist of fluidized deformation, synsedimentary faults, seismo-folds and plastic deformation; the Mantou Formation is dominated by small-scale horst faults, intruded dikes, fluidized veins, and seismo-cracks. These structures are demonstrated to be earthquake-related by analysis of trigger mechanisms, and may indicate the activity of the Qinling tectonic belt during the early Cambrian. Furthermore, the assemblages of soft-sediment deformation structures altered with time： large-scale, intense deformation in the Zhushadong Formation alters to small-scale, weak deformation in the Mantou Formation. This striking feature may have been caused by changes in hypocentral depth from deep-focus to shallow-focus earthquakes, indicating that the Qinling tectonic belt developed from the subduction of the Shangdan Ocean to the extension of the Erlangping back-arc basin. This study suggests that soft-sediment deformation structures can be used to reveal the activity of a tectonic belt, and, more importantly, changes in deformation assemblages can track the evolution of a tectonic belt.

Multi-scale Decomposition of Co-seismic Deformation from High Resolution DEMs:a Case Study of the 2004 Mid-Niigata Earthquake

Decomposing co-seismic deformation is an immediate need for researchers who are interested in earthquake inversion analysis and geo-hazard mapping. However, conventional InSAR or digital elevation models （DEMs） imagery analyses only provide the displacement in the Line-of-Sight （LOS） direction or elevation changes. The 2004 Mid-Niigata earthquake in Japan provides lessons on how to decompose co-seismic deformation from two sets of DEMs. If three adjacent points undergo a rigid-body-translation movement, their co-seismic deformation can be decomposed by solving simultaneous equations. Although this method has been successfully used to discuss tectonic deformations, the algorithm needed improvement and a more rigorous algorithm, including a new definition of nominal plane, DEMs comparability improvement and matrix condition check is provided. Even with these procedures, the obtained decomposed displacement often showed remarkable scatter prompting the use of the moving average method, which was used to determine both tectonic and localized displacement characteristics. A cut-off window and a pair of band-pass windows were selected according to the regional geology and construction activities to ease the tectonic and localized displacement calculations, respectively. The displacement field of the tectonic scale shows two major clusters of large lateral components, and coincidently major visible landslides were found mostly within them. The localized displacement helps to reveal hidden landslides in the target area. As far as the Kizawa hamlet is concerned, the obtained vectors show down-slope movements, which are consistent with the observed traces of dislocations that were found in the Kizawa tunnel and irrigation wells. The method proposed has great potential to be applied to understanding post-earthquake rehabilitation in other areas.

TECTONIC DEFORMATION AND STRONG EARTHQUAKE ACTIVITIES ON THE EAST BORDER OF TIBET PLATEAU

The tectonic deformation image of Asia Continent can be explained successfully by the model of collision between India secondary continent and Euro\|Asia Plate (P. Molnar and P.Tapponnier, 1975). This paper mainly discusses the characteristics of tectonic deformation and strong earthquake activities on the east border of Tibet Plateau.1\ Characteristics of tectonic deformation on the east border of Tibet Plateau\;Controlled by the flow of the plateau crust material, the movement of the east border of Tibet plateau is mainly horizontal so as to produce two slipping\|block: one results from the slide out of Chuandian Rhombus Block along the SSE direction, the other results from the lateral extrusion of Chuanqing Block with the SEE direction. The slip rate of the north part of Chuandian Rhombus Block, the west region of Sichuan, is 5～8mm/a;2～3mm/a on the south part (the center part of Yunan); the slip rate of Chuanqing is 3～5mm/a and <1mm/a on Longmenshan region (Tang Rongchang, 1993). The slipping features of the blocks directly decide the movement characters of different fault systems: the uniform sinistral shear movement on the east boundary fault of Chuandian Rhombus Block, from the geological viewpoint, the average horizontal slip rate is about 10mm/a, and 5～8mm/a on the Anninghe, Zemuhe and Xiaojiang faults. The dextral shear movement can be found on the west boundary faults composed by Jinshajiang and Honghe faults. Located at the dextral diagonal region between Honghe and Zhongdian faults, the northwestern region of Yunnan shows a tensile stress field with near EW direction and large graben valleys with near NS direction on the ground due to the dextral slip movements of these two faults and slip of Chuandian Rhombus Block along the SSE direction. The normal features of extension tectonic deformation region can be found in this region. Some inner faults (such as Amaniqing, Xiqinglingbeilu) of Chuanqing block show the character of sinistral shear movement with some components of normal slip movement. As the east boundary of Tibet plateau, Minshan and Longmenshan Mountains form the east wall of the plateau. Contrasting to the moving direction of Chuanqing block, the transition from horizontal movement to vertical movement produced the huge nappe reverse deformation in this region, and formed some front\|Mount compensating press\|sag basins such as Gonggaling, Zhangla and Chengdu. Because of the diversity of slip rate of different boundary faults, some clockwise rotating movement can be found in different sub\|blocks.

An Inverse Analysis of the Comprehensive Medium Parameters and a Simulation of the Crustal Deformation of the Qinghai-Tibet Plateau

Based on the theory of finite element analysis, an inverse analysis model for the comprehensive medium parameters of the Qinghai-Tibet Plateau is set up. With the help of GPS velocity field, the comprehensive crustal medium parameters of the plateau are inversely analyzed and the characteristics of the related movement macroscopically simulated. It is then concluded that the tectonic deformation of the plateau is mainly in the form of a N-S compression accompanied by an E-W stretching, and the present tectonic setting of the plateau should be the result of the collision between the Indian and the Eurasian continents during the Cenozoic.

Relation between electricity structure of the crust and deformation of crustal blocks on the northeastern margin of Qinghai-Tibet Plateau

Study on the electricity structure along a magnetotelluric(MT)sounding profile on the northeastern margin of Qinghai-Tibet Plateau indicates that four crustal blocks can be de-termined from southwest to northeast,namely Bayan Har block(BH),Qin-Qi block(QQ),Hai-yuan block(HY)or the North-South seismotectonic belt and Ordos block(OD).The BH,QQ and OD blocks display a similar electricity structure of the crust.The upper crust represents a high-resistivity layer and the upper part of lower crust represents a low-resistivity layer with the resis-tivity increasing gradually with depth from the lower part of lower crust to the upper mantle.The electricity structure of the crust in these three blocks is similar to that in the complete blocks on the southern and eastern margins of the Qinghai-Tibet Plateau and belongs to normal electricity layering of the crust in slightly deformed or complete intracontinental blocks.The crust in HY block as a boundary zone has been significantly deformed,hence its electricity layering was de-stroyed and the structure was complex and the block became a recent tectonically active and great seismo-active region.The contact belts between the blocks on the northeastern margin of Qinghai-Tibet Plateau exhibit both upthrusting outward and strike-slip movement different from those on the southern and eastern margins of the plateau.The genesis of the low-resistivity layer in the crust is analyzed and the thickness of the lithosphere is estimated in the paper.

Early Mesozoic structural deformation in the Chuandian N-S Tectonic Belt,China

The Helan-Chuandian N-S Tectonic Belt is a mantle transitional belt in China. The southem part, forming the Chuandian N-S Tectonic Belt, comprises several tectonic systems, each displaying different characteristics. The Chuandian N-S Tectonic Belt along the western margin of yangtze Block is a strike-slip tectonic belt with a series of echelon left-lateral slip faults. The strike-slip fault systems experienced two stages of structural deformation： early NW-SE striking thrust faults formed under a NE-SW compression stress field, and later sinistral strike-slip structures formed along thrust faults under a NW-SE compression stress field. Mesozoic basins developed between the left-lateral slip faults. Sedimentary facies and paleocurrent directions indicate that basin development was controlled by the strike-slip faults. The oldest strata in the Chuandian N-S Tectonic Belt constrain its formation to early Mesozoic. In fact, The slip tectonic belt formed by clockwise rotation and north-directed subduction-collision of the Yangtze Block in Late Triassic-Jurassic. The strike-slip faults that developed within the belt also formed at this time.

Stress-Deformed State of Geological Environment and Prognosis of Antropogenic-Tectonic Earthquakes

The highest priorities of any civilized country are in providing interests of social safety.The anthropogenic influence on geological environment is becoming greater because of the human activities increase. That’s why anthropogenic-tectonic earthquake problem has become important recently.It appeared as a hypothesis in the 30 s and became much clearer in 60 s.The anthropogenic-tectonic earthquake epiceneters are located not far from the surface and,as a rule。

东昆仑西段岩碧山构造混杂带构造变形特征及就位机制研究

岩碧山构造混杂岩带,位于南昆仑地块北侧,东与畅流沟—向阳泉蛇绿混杂岩相连,东南汇入木孜塔格—布青山蛇绿构造混杂岩带,近北西西向发育以逆冲及走滑性质构造系为主体,叠加了晚期逆冲推覆构造的混杂岩带(邵东等,2017)(图1)。根据岩碧山构造混杂岩带的物质特征,将其划分为早古生代岛弧型、变质基底、洋壳杂岩3类岩块,长英质糜棱岩、构造碎裂岩2类基质和晚古生代洋盆演化相关的洋壳杂岩组成。

Geological modeling of coalbed methane reservoirs in the tectonically deformed coal seam group in the Dahebian block,western Guizhou,China

The widely spread Carboniferous-Permian coal seam group in southern China has great potential for coalbed methane resources,but the extensively developed tectonically deformed coal seriously restricts its development.Taking the Dahebian block in western Guizhou as the study area,the geological model of coalbed methane reservoirs in the tectonically deformed coal seam group was established,and the spatial distribution pattern of model parameters was clarified by clustering algorithms and factor analysis.The facies model suggests that the main coal body structures in Nos.1,4,and 7 coal seams are cataclastic coal and granulated coal,whereas the No.11 coal seam is dominated by granulated coal,which has larger thicknesses and spreads more continuously.The in situ permeability of primary undeformed coal,cataclastic coal,granulated coal,and mylonitized coal reservoirs are 0.333 mD,0.931 mD,0.146 mD,and 0.099 mD,respectively,according to the production performance analysis method.The property model constructed by facies-controlled modeling reveals that Nos.1,4,and 7 coal seams have a wider high-permeability area,but the gas content is lower;the high-permeability area in the No.11 coal seam is more limited,but the gas content is higher.The results of the self-organizing map neural network and K-means clustering indicate that the geological model can be divided into 6 clusters,the model parameter characteristics of the 6 clusters are summarized by data analysis in combination with 6 factors extracted by factor analysis,and the application of data analysis results in multi-layer coalbed methane co-development is presented.This study provides ideas for the geological modeling in the tectonically deformed coal seam group and its data analysis.

中国大陆活动地块边界带与强震活动

本文在前人对中国大陆及周边活动地块研究和划分的基础上,系统研究了6个Ⅰ级活动地块区和2 2个Ⅱ级活动地块之间共2 6个活动边界带的构造变形与强震活动,包括强震分布与活动边界带的关系,边界带构造活动速率与地震活动水平及强震复发期等的关系.给出了边界带强震活动水平与构造活动速率之间的线性关系和强震复发期长短与构造活动速率的反向变化关系.从而进一步揭示了中国大陆活动地块构造及其块体运动特征,以及块体边界带的构造变形对强震的控制作用.

大陆构造变形与地震活动——以青藏高原为例

大陆内部构造变形和地震活动往往突显出复杂的、区域性的特征,很难用板块构造理论来解释。青藏高原是大陆构造变形的典型实例,具有不同构造变形的分区特征,不仅表现在物质组成、地形地貌和断裂组合等方面的不同,而且还表现出不同的地震活动特征。东昆仑断裂带以北的青藏高原北部地块,主要发育一系列挤压环境下的盆岭构造,表现为以连续变形为特征的上地壳挤压缩短变形;高原中北部巴颜喀拉地块,具有整体向东运动的特点,变形主要集中在其边缘,表现为刚性块体运动特征。在东部,由于稳定的四川盆地(扬子地块)的阻挡,位于龙日坝和龙门山断裂带之间相对坚硬的龙门山地区受到东西向强烈挤压,西部边界为伸展变形;在高原中央腹地羌塘地块西部,由于上地壳物质在向东挤出的驱动下不断变形,沿一系列小型正断层和走滑断层以伸展变形为主,表现为弥散型变形特征。相比之下,羌塘地块的东部向东-南东方向挤出,在大型走滑断层之间形成一个刚性块体;高原南部地块以东西向伸展的南北向裂谷系为主要变形特征,高原南缘以南北向挤压的大型逆冲断裂系为特征。历史地震和仪器记录的大地震(M≥8)只发生在高原东北和东南部的大型走滑带,以及东部和南部边缘的大型逆冲断裂上,沿后者更为频发。到目前为止,高原其他地区只发生了8级以下地震。青藏高原这种分区域的地壳变形形式和地震活动分布是大陆构造变形的重要特征。

LiDAR技术在活动构造研究中的应用

沿断裂带的大比例尺地貌填图是活动构造研究的重要基础。传统方法一般通过遥感、航片解译以及典型地点的实地测量进行详细填图。因此传统方法一般只能获得二维变形特征,或者局部的三维变形。激光雷达测量(Light Detection And Ranging-LiDAR)技术优势为对地貌的高精度、全方位、三维直接测量,可以为活动构造研究提供沿整条断裂带的高精度地貌高程基础数据。基于LiDAR数据的量化分析是未来活动构造研究的趋势。目前,美国、欧洲、日本以及我国台湾地区等均已经开展沿主要活动断裂带的大规模机载LiDAR测量。与传统方法相比,LiDAR技术在森林覆盖区和城区的活动断裂填图中具有巨大的优势,在沿断裂位错测量上也更精准,更有效。并且震前与震后LiDAR数据对比也是研究同震变形特征、探索断裂发震模式的重要手段。本文综述LiDAR技术在活动构造研究中的主要应用,介绍LiDAR技术在活动构造研究中的优势与前景。分析表明,激光雷达技术在活动构造研究中的应用势在必行,沿国内主要活动断裂带的机载LiDAR测量将成为未来国内活动断裂研究基础数据获取的重要手段。

临汾与保德地区构造差异性特征及其对煤层含气性的控制

为研究鄂尔多斯盆地东缘煤层含气性的构造控制作用,在野外构造变形特征系统研究的基础上,结合区域构造背景分析及构造应力场恢复,揭示了鄂尔多斯盆地东缘临汾和保德区块构造发育的差异性特征及其对煤储层含气性的控制作用。结果表明:研究区主要经历了燕山期NW—SE向的构造挤压作用和喜马拉雅期NW—SE向的伸展作用;南部临汾区块燕山期NW—SE向的挤压作用强烈,发育NE—NNE向的逆冲断层和次级宽缓褶皱构造等,有利于煤层气的保存,即使后期叠加了一定的喜马拉雅期NW—SE向的伸展作用,使煤层气部分散失,但总体含量较高,且高值区与构造位置相关性很好;北部保德区块燕山期挤压构造变形作用不显著,喜马拉雅期NW—SE向的伸展作用较突出,NE向正断层较为发育,为煤层气的运移及散失提供了条件,致使煤层含气量相对较低。

川滇地区现代地壳运动速度场和活动块体模型研究

通过分析中国地壳运动观测网络的GPS数据得到川滇地区地壳水平运动速度场 ,由此划分活动块体并分析其运动特征。结果表明 :相对欧亚板块 ,滇中、雅江和中甸次级块体的顺时针转动速率分别为 0 37°± 0 16°/Ma ,0 84°± 0 39°/Ma和 0 90°± 0 39°/Ma ,造成块体间跨木里弧形断裂带约 3mm/a的SN向挤压、丽江 -大理断裂带约 4mm/a的EW向拉张和理塘断裂带约 6mm/a的近EW向拉张。鲜水河断裂带左旋走滑速率 8～ 10mm/a ,安宁河 -则木河 -小江断裂带左旋走滑 5～6mm/a。龙门山断裂带没有明显的地壳消减 ,而断裂带西北约 15 0km处有一形变速度阶跃带 ,右旋走滑速率 4～ 5mm/a。阶跃带两侧的岷山块体和阿坝地区逆时针转动速率分别为 0 13°± 0 0 8°/Ma和0 5 3°± 0 19°/Ma。鲜水河 -小江断裂带以南、以西地区 ,青藏高原物质的E向挤出和重力滑塌造成川滇块体东移 ,在东部相对稳定的华南地块的阻挡下 ,川滇块体沿鲜水河 -小江断裂带由东转向南运动 ,从而引起川滇块体内部各次级块体的顺时针转动。

由GPS观测结果推断中国大陆活动构造边界

利用“中国地壳运动观测网络”基本网 1998年和 2 0 0 0年两期观测数据 ,得到分布在全国各构造块体上的79个GPS观测站速度场 ,对中国大陆主要活动构造块体间的相对运动显著性进行了分析和检验 .分析结果表明 ,西部活动构造块体的边界有较明显的相对运动 ,而东部运动不明显 .根据分析得到的活动边界 ,将中国大陆归并为11个活动块体 ,逐一计算了这些块体边界的活动量大小 ,确定了它们最新活动的方式 .

下扬子南黄海沉积盆地构造地质特征

南黄海盆地作为下扬子块体之上的大型叠合盆地,海相构造层保存完整,陆相断拗构造层也较为发育,盆地地质结构复杂,构造变形强烈,利用最新的地质地球物理资料和解释成果,对低勘探程度的南黄海盆地进行了研究,认为盆地演化大致经历了克拉通被动陆缘初始发育阶段—南缘前陆北缘被动陆缘过渡阶段—南北对冲前陆定型阶段—滨太平洋弧后陆内调整四个阶段。南黄海盆地属于台地—断拗复合地质结构,中、新生代为具有盆内隆起带的断陷箕状结构,且中、新生代多期构造运动在盆地原型改造和后期沉积发育上起着至关重要的作用,尤其印支—燕山早期运动、燕山中期黄桥运动和喜马拉雅期盐城运动与盆地地层变形、沉积发育、断裂发育及构造样式等盆地要素演化密切相关,进而导致盆地垂向地质结构和构造变形的层次性极为显著,而中生代燕山期和新生代喜马拉雅期两期构造岩浆活动则与滨太平洋域的动力学背景相关。

青藏活动地块区运动与变形特征的数值模拟

利用二维有限元模型,以GPS测量的构造运动为约束条件,探讨了青藏活动地块在弹性应变积累过程中的运动与变形状态。模拟结果表明,青藏活动地块区在整体运动过程中,内部变形以大范围的分布为特征,其内部的应变分布和弹性应变能积累速率表明了Ⅱ级活动地块与活动边界带的显著变形差别活动地块内部的应变和弹性应变能积累速率相对较小且分布较均匀;活动边界带上变形相对集中,应变和弹性应变能积累速率相对较高,并呈非均匀分布。这反映了青藏地块区内所含的各Ⅱ级活动地块的运动变形的整体性特征及彼此间的差异性特征,也揭示了活动地块构造通过边界带变形等方式对大陆强震的控制作用。

华南块体的现今构造运动与内部形变

运用华南块体及周围地区最新的GPS观测结果,研究了华南块体的现今构造运动。华南块体无论是相对于欧亚板块或相对于西伯利亚块体都存在逆时针方向的旋转。由GPS观测结果得到的华南块体相对于西伯利亚块体的现今旋转运动与由地质学和地球物理学方法得到的自晚新生代以来华南块体相对于西伯利亚的旋转运动相比,运动速率相同,但运动方向顺时针旋转了20.7°。