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1.
The long-period Rayleigh waves were investigated for the largest four deep shocks in 1963–1973 to determine the seismic moment by the same technique as used for shallow earthquakes. The results could be used for a quantitative comparison of source parameters between shallow and deep events. Three of the four shocks occurred beneath the South American continent (the Colombia earthquake, 1970; the western Brazil earthquake, 1963; the Peru—Bolivia border earthquake, 1963) and the other beneath the Japan Sea (1973). The focal depths are 653, 576, 593 and 575 km, respectively. The largest value of seismic moment was obtained as 2.1 · 1028 dyncm for the Colombia earthquake. This value is still about forty times smaller than that for the great Alaskan earthquake. A slight inconsistency was found between the first-motion diagram and the Rayleigh wave radiation pattern for the Colombia earthquake and the Peru—Bolivia border earthquake. 相似文献
2.
Regional metamorphic belts of the Japanese Islands 总被引：1，自引：0，他引：1
Abstract An overview of the regional metamorphic belts of Japan is given in the context of the tectonic evolution of the Japanese Islands. The Japanese Islands were situated on an active margin of the Eurasian continent or its constituent landmass before their assembly during the Phanerozoic. The Japanese Islands are composed mainly of metamorphosed and unmetamorphosed accretionary complexes, granitoids and their effusive equivalents that were formed by the Cordilleran-type orogeny. The metamorphic belts are regarded essentially as a deep-seated portion of an accretionary complex. In spite of continuous subduction of oceanic plates beneath the continents, these orogenic rocks were formed quite episodically, as evidenced by discontinuous matrix ages of the accretionary complexes and a striking concentration of isotopic ages of the granitoids. A systematic along-arc age shift of Cretaceous large-scaled granitic magmatism and regional metamorphism suggests a tectonic control such as ridge subduction, which triggered the episodic orogeny. A tectonic model based on the paired metamorphic belts, combined with the non-steady tectonic control, works well to explain this magmatism and metamorphism in a single arc-trench system as a continental margin process. However, the juxtapositional process of the paired metamorphic belts is still a problem. Two possible cases, namely transcurrent displacement and back-arc overthrusting are discussed. 相似文献
3.
Seismic tomography beneath the orogenic belts and adjacent basins of northwestern China 总被引：2，自引：0，他引：2
Three-dimensional velocity images of the crust and upper mantle beneath orogenic belts and adjacent basins of the northwestern
continent of China are reconstructed by seismic tomography, based on arrival data of P wave recorded in seismic networks in
Xinjiang, Qinghai, Gansu of China and Kyrgyzstan. The velocity images of upper crust demonstrate the tectonic framework on
the ground surface. High velocities are observed beneath orogenic belts, and low velocities are observed in the basins and
depressions that are obviously related to unconsolidated sediments. The velocity image in mid-crust maintains the above features,
and in addition low velocities appear in some earthquake regions and a low velocity boundary separates the western Tianshan
Mts. from eastern Tianshan Mts. The orogenic belts and the northern Tibetan plateau have a Moho depth over 50 km, whereas
the depths of the Moho in basins and depressions are smaller than 50 km. The velocity images of upper mantle clearly reveal
the colliding relationship and location of deep boundaries of the continental blocks in northwestern China, indicating a weakness
of the upper mantle structure of orogenic belts. The top depth of upper mantle asthenosphere varies from place to place. It
seems shallower under the northern Tibetan plateau, Altay and Qilian Mts., and deeper under the Tarim and Tianshan regions.
Hot mantle probably rose to the bottom of some orogenic belts along tectonic boundaries when continental blocks collided to
each other. Therefore their dynamic features are closely correlated to the formation and evolution of orogenic belts in northwestern
China. 相似文献
4.
Characteristics of mantle degassing and deep-seated geological structures in different typical fault zones of China 总被引：2，自引：1，他引：2
TAO Mingxin XU Yongchang SHI Baoguang JIANG Zhongti SHEN Ping LI Xiaobin & SUN Mingliang . Key Laboratory of Gas Geochemistry Lanzhou Institute of Geology Chinese Academy of Sciences Lanzhou China . Beijing Normal University Beijing China . The Practical Geologic Data Center State Land Resource Department Sanhe China 《中国科学D辑(英文版)》2005,48(7)
Large-scale fault zones play an important role in controlling and adjusting all kinds of geological proc-esses,such as deposition,magmatism,metamorphism,metallogenesis,tectonic stress field,tectonic deforma-tion,even the movement of geological massifs,earth-quakes,and they also are the key to solving geological problems concerned,especially regional and even global structures.Due to their special geological tec-tonic significance,they are one of the main research fields of tectonic geology and … 相似文献
5.
A. Keith Martin Chris J.H. Hartnady Stephen W. Goodlad 《Earth and Planetary Science Letters》1981,54(2):293-305
A new set of parameters for the total plate tectonic reconstruction of South America and south central Africa is presented: euler pole 46.75°N, 32.65°W; rotation angle 56.40°. This fit is constrained by at least three pre-drift tectonic features crossing from one continent to the other: (1) the geophysically defined eastern and western boundaries of the submarine Jurassic Outeniqua Basin (South Africa) and the Falkland Plateau Basin; (2) the Late Precambrian transcurrent fault and mylonite belts of Pernambuco (Brazil) and Foumban (West Africa); and (3) the Triassic northern tectonic front of the Cape Fold Belt and the major morphological feature on the Falkland Plateau with which it is closely lined up. Isotopic ages of Falkland Plateau gneisses correspond to Cape Pluton and Cape Fold Belt ages, suggesting their palaeoposition was within the realm of the Cape Fold Belt.In addition, the bathymetrically and geophysically defined northeastern apex of the Falkland Plateau fits into the re-entrant angle defined on the South African margin by the steep southeast-facing sheared Agulhas margin and the southern face of the Tugela Cone. Simultaneously known Precambrian outcrops in northeastern Brazil and in the Gulf of Benin area of West Africa are juxtaposed rather than overlapped. Reconstructions producing a closer fit of these cratonic areas are considered untenable. 相似文献
6.
7.
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
8.
构造热演化模拟是研究沉积盆地的重要手段之一，其模型依赖于沉积盆地的成因机制.裂谷盆地构造热演化的定量模型在描述盆地沉降和热流演化方面取得了极大的成功，实现了构造和热的完美结合.而前陆盆地的定量模型更多关注的是构造沉降，在构造与热的结合方面尚不够完善.关于克拉通盆地目前还没有很成熟的定量模型，构造热演化研究程度远远低于裂谷盆地和前陆盆地.随着我国陆域海相沉积盆地油气勘探的突破，对海相沉积盆地热体制的研究迫在眉睫.而我国陆域海相沉积盆地，如塔里木和四川盆地，演化历史长且复杂，是古生代海相克拉通与中、新生代前陆盆地组成的叠合盆地.现有的关于沉积盆地构造热演化的单一模式难以适应复杂的构造—热历史.对我国陆域海相大型沉积盆地进行深入全面的动力学分析，发展叠合盆地的构造—热演化模型，建立相应的构造热演化模式及模拟方法技术，将是一项具有开拓意义并极具挑战性的工作. 相似文献
9.
Heat flow anomalies and their interpretation 总被引：1，自引：0，他引：1
More than 10,000 heat flow determinations exist for the earth and the data set is growing steadily at about 450 observations per year. If heat flow is considered as a surface expression of geothermal processes at depth, the analysis of the data set should reveal properties of those thermal processes. They do, but on a variety of scales. For this review heat flow maps are classified by 4 different horizontal scales of 10n km (n = 1, 2, 3 and 4) and attention is focussed on the interpretation of anomalies which appear with characteristic dimensions of 10(n − 1) km in the respective representations.The largest scale of 104 km encompasses heat flow on a global scale. Global heat loss is 4 × 1013 W and the process of sea floor spreading is the principal agent in delivering much of this heat to the surface. Correspondingly, active ocean ridge systems produce the most prominent heat flow anomalies at this scale with characteristic widths of 103 km. Shields, with similar dimensions, exhibit negative anomalies.The scale of 103 km includes continent wide displays. Heat flow patterns at this scale mimic tectonic units which have dimensions of a few times 102 km, although the thermal boundaries between these units are sometimes sharp. Heat flow anomalies at this scale also result from plate tectonic processes, and are associated with arc volcanism, back arc basins, hot spot traces, and continental rifting. There are major controversies about the extent to which these surface thermal provinces reflect upper mantle thermal conditions, and also about the origin and evolution of the thermal state of continental lithosphere.Beginning with map dimensions of 102 km thermal anomalies of scale 101 km, which have a definite crustal origin, become apparent. The origin may be tectonic, geologic, or hydrologic. Ten kilometers is a common wavelength of topographic relief which drives many groundwater flow systems producing thermal anomalies. The largest recognized continental geothermal systems have thermal anomalies 101 km wide and are capable of producing hundreds of megawatts of thermal energy.The smallest scale addressed in this paper is 101 km. Worldwide interest in exploiting geothermal systems has been responsible for a recent accumulation of heat flow data on the smallest of scales considered here. The exploration nature of the surveys involve 10's of drillholes and reveal thermal anomalies having widths of 100 km. These are almost certainly connected to surface and subsurface fluid discharge systems which, in spite of their restricted size, are typically delivering 10 MW of heat to the near surface environment. 相似文献
10.
Ute Weckmann 《Surveys in Geophysics》2012,33(1):107-134
The African continent inherits a long history of continental accretion and breakup. The stage of “making” a continent goes
back to the Archean, when the first continental masses formed cratons which mostly remained stable ever since. Subsequent
collision of weaker continental masses was followed by several extension and compression episodes that resulted in the formation
of super-continents. After the assemblage of Gondwana, a period of predominantly “breaking” , i.e., the breakup of super-continents,
took over. The modern-day African continent exhibits different types of margins; continental rifting occurs side by side with
recent collision. Since the late 1960s, magnetotelluric (MT) experiments have played an important role in studies of the electrical
conductivity structure of Africa. The early results significantly shaped the MT community’s understanding of continental-scale
conductivity belts and basic characteristics of cratons and mobile belts on both crustal and lithospheric mantle scales for
some decades. Modern MT studies in Africa have generally supported earlier results with high resistivities observed on cratons
and low resistivities observed across mobile belts. Advances in instrumentation, data processing and interpretation resulted
in higher-resolution images of the lithosphere, which in consequence induce an improved understanding of tectonic processes
and geological prerequisites for the occurrence of natural resources. The high electrical conductivity of mobile belts and
their relation to reactivated fault and detachment zones were often interpreted to characterize mobile belts as tectonic weak
zones, which can accommodate stress and constitute zones along which continents can break. Recent breaking of the African
continent can be studied on land across the East African rift; however, the lack of amphibian MT experiments across today’s
margins does not allow for good resolution of remnants of continental breakup processes. Naturally, the regions and the focus
of the MT studies in Africa are diverse, but they all contribute to the story of making and breaking a continent. 相似文献
11.
《Physics of the Earth and Planetary Interiors》1982,28(3):261-268
The Runcorn stress equations and 2–30° harmonic coefficients of the geopotential have been applied to determine the mantle convection pattern beneath China. The pattern is compared with geophysical and geological observations and it is found that the directional change belts of mantle flows coincide with the major fault belts between tectonic units of China. The stress field generated by mantle flows, except in the Tian Shan region, also coincide with the stress field of recent tectonic movement in China. The Tarim and Junggar basins are formed by tensional stresses due to divergent mantle convection currents under northwest China. The formation of the Qinhai-Xizang (Tibet) plateau is due mainly to the compression of the Tarim block and Indian plate, caused by convergent mantle convection currents. The shear-fault belts in central China (100–105°E) are generated by the running change belt of mantle flows, a well-known N-S seismic zone. In eastern China, tensional faults, grabens, lake and sea depressions are related to the eastward displacement of continental lithosphere exerted by eastward dispersal mantle flows under this region.This paper provides new material for further study of the force source mechanism of recent tectonic movement from the viewpoint of mantle convection currents. 相似文献
12.
岩石圈下层的网状塑性流动 ,作为包含塑性流动网络的黏塑性流动 ,控制着大陆板块内部的构造变形和动力学过程。塑性流动网络由两组网带共轭相交而成 ,而塑性流动网带是黏塑性流动过程中因剪切局部化、黏性摩擦生热和网带介质的弱化而形成的延性弱面 (弱带 )。研究表明 ,类似于断裂和节理等脆性弱面 ,延性弱面对介质强度的影响也具有条件性 ,即当应力方向改变时 ,只有在滑移角θ不超出一定限值的条件 (θ1≤θ≤θ2 )下才可能沿原有弱面滑移 ,显示其弱化效应 ;延性弱面可以用弱化度R表示其屈服限的相对降低程度 ,弱化度与滑移角下限值之间的关系为R =sin2θ1;根据亚洲中东部地区“塑性流动 -地震”网络的最大共轭角推算 ,网带的弱化度R近似于 0 81。基于延性弱面效应的认识 ,文中就网带由剪切滑移向压性褶皱的转化、网带的继承与弃置以及应力方向的允许偏角等问题进行了探讨 相似文献
13.
本文报道了莺歌海盆地、北部湾盆地共148个新测热导率数据,根据收集的钻井温度数据新增计算65个大地热流数据;结合前人研究成果绘制了南海北部大陆边缘沉积盆地的地温梯度图、大地热流分布图;系统归纳了南海北部大陆边缘油气勘探成果.结果表明,南海北部大陆边缘珠江口盆地、琼东南盆地、北部湾盆地、莺歌海盆地的平均热流值分别为68.7±11 mW/m2、71.1±13 mW/m2、65.7±8.9 mW/m2、74.7±10 mW/m2,属于典型的“热盆”.热流区域分布特征总体上受大地构造背景控制,随地壳厚度从北向南,由陆架到陆坡区逐渐减薄而增高,水热活动与岩浆活动等是引起局部高热流异常的原因.盆地地温场的差异控制和约束了油气分布富集规律,从研究区油气勘探成果中可以发现,该区域的气田多发育于高热流盆地（凹陷）,而中-低热流盆地（凹陷）则多孕育油田,油气田具有“北油南气”的分布特征. 相似文献
14.
Northward subduction of the Cenozoic Tethys ocean caused the convergence and collision of Eurasia-Indian Plates, resulting in the lower crust thickening, the upper crust thrusting, and the Qinghai-Tibet uplifting, and forming the plateau landscape. In company with uplifting and northward extruding of the Tibetan plateau, the contractional tectonic deformations persistently spread outward, building a gigantic basin-range system around the Tibetan plateau. This system is herein termed as the Circum-Tibetan Plateau Basin-Range System, in which the global largest diffuse and the most energetic intra-continental deformations were involved, and populations of inheritance foreland basins or thrust belts were developed along the margins of ancient cratonic plates due to the effects of the cratonic amalgamation, crust differentiation, orogen rejuvenation, and basin subsidence. There are three primary tectonic units in the Circum-Tibet Plateau Basin-Range System, which are the reactivated ancient orogens, the foreland thrust belts, and the miniature cratonic basins. The Circum-Tibetan Plateau Basin-Range System is a gigantic deformation system and particular Himalayan tectonic domain in central-western China and is comparable to the Tibetan Plateau. In this system, northward and eastward developments of thrust deformations exhibit an arc-shaped area along the Kunlun-Altyn-Qilian-Longmenshan mountain belts, and further expand outward to the Altai-Yinshan-Luliangshan-Huayingshan mountain belts during the Late Cenozoic sustained collision of Indo-Asia. Intense intra-continental deformations lead ancient orogens to rejuvenate, young foreland basins to form in-between orogens and cratons, and thrusts to propagate from orogens to cratons in successive order. Driven by the Eurasia-Indian collision and its far field effects, both deformation and basin-range couplings in the arc-shaped area decrease from south to north. When a single basin-range unit is focused on, deformations become younger and younger together with more and more simple structural styles from piedmonts to craton interiors. In the Circum-Tibetan Plateau Basin-Range System, it presents three segmented tectonic deformational patterns: propagating in the west, growth-overthrusting in the middle, and slip-uplifting in the east. For natural gas exploration, two tectonic units, both the Paleozoic cratonic basins and the Cenozoic foreland thrust belts, are important because hydrocarbon in central-western China is preserved mainly in the Paleozoic cratonic paleo-highs and the Meso-Cenozoic foreland thrust belts, together with characteristics of multiphrase hydrocarbon generation but late accumulation and enrichment. 相似文献
15.
中国西部地区是地震活动十分强烈的地区,天山、阿尔泰、帕米尔和西昆仑都是著名的地震构造带,在这些地震构造带和周边地区发生了多次震级大于5级的强震.本文通过分析西部地区的重力场特征,根据重力数据结合地震剖面、应用Parker-Oldenburg方法反演得到了研究区莫霍面深度,通过对比地震层析成像的反演结果,分析了研究区的地壳结构特征.计算结果表明,研究区地壳结构不均匀特征明显,在造山带地区一般是莫霍面坳陷区,盆地则是莫霍面隆起区,主要造山带地壳速度结构表现为高速区,盆地和主要凹陷区为低速区.根据计算结果和以往强震震中位置分析了地壳构造与强震活动的相关性,西部地区的地震活动与地壳结构的横向不均匀密切相关,强震主要发生在地壳速度变化带附近和地壳速度结构差异较大的地区,在构造应力作用下,这些地壳介质非均匀地区易发生强震,这是中国西部造山带和盆-山边界附近频发强震的构造原因之一. 相似文献
16.
Depth distribution of Moho and tectonic framework in eastern Asian continent and its adjacent ocean areas 总被引：3，自引：0，他引：3
It is the essence of the study on the dynamics of eastern Asian continent to investigate the ef-fects of geophysical field and the process of the deep block boundaries, and furthermore, to estab-lish a geodynamic physical-mathematical model based on the d… 相似文献
17.
利用重、磁和天然地震资料对中南地区进行了综合地质地球物理研究.根据研究区的重、磁异常的分布特征,可将其分为4个重力异常区、3个航磁异常区.根据重力资料反演计算得到的研究区的地壳厚度在295～41 km之间,总的趋势为西厚东薄,地壳厚度与地形起伏基本上呈镜像关系.根据磁力资料计算得到的研究区居里界面在12～40 km之间变化.地震层析成像结果表明研究区内的速度分布总体上体现了纵横交错的断块特征.在纵向尺度上,江汉－洞庭盆地以及周缘造山带的上地壳结构变化不大,中地壳和下地壳则普遍受到现今构造活动的改造,以致岩石的结构发生了一定的变化.它们主要表现为低速区域的扩大,尤其是在地壳下部尤为突出,这与断陷盆地的拉张以及造山带岩石层的底侵和拆沉作用密切相关.通过对研究区地球物理场的分析计算,在研究区共提取主要断裂带34条.根据岩石层板块大地构造理论,依据岩石层结构、地壳结构和结晶基底等深部结构的不同,将研究区中板内不同构造单元——块体作为一级构造单元,块体之间的深大断裂带作为块体的边界——块体结合带,据此原则在研究区中划分出两个一级构造单元,五个二级构造单元. 相似文献
18.
华南大陆记录和保存了自太古代至今大陆生长层完整的历史过程.以杨子克拉通为核心，地壳不断向东南生长，古扬子块前寒武系以灰色片麻岩、古元古代科马提岩绿岩、新元古代蛇绿岩、绿岩为特征，为相对稳定高速高阻冷的残存地幔“残烃柱”；而沿海一带火成岩以中、新生代壳－幔混合源火山－侵入杂岩、碱性花岗岩和正长岩带以及不同类型的玄武岩类为特征，为相对活动低速高导热的超地幔柱．巨型裂解构造是物质热传输的主要形式，地幔柱迁移是华南大陆构造演化的原动力． 相似文献
19.
Chile is a very important country that forms part of the Andean metallogenic belts. The Atacama and Domeyko fault systems in northern Chile control the tectonic–magmatic activities that migrate eastward and the types of mineral resources. In this paper, we processed and interpreted aeromagnetic data from northern Chile using reduction to pole, upward field continuation, the second derivative calculation in the vertical direction, inclination angle calculation, and analytical signal amplitude analysis. We revealed the locations and planar distribution characteristics of the regional deep faults along the NNE and NS directions. Furthermore, we observed that the major reasons for the formation of the tectonic–magmatic rocks belts were the nearly parallel deep faults distributed from west to east and multiple magmatic activities along these faults. We ascertained the locations of volcanic mechanisms and the relationships between them using these regional deep faults. We deduced the spatial distributions of the basic–intermediate, basic, and acidic igneous rocks, intrusive rocks, and sedimentary sequences. We showed the linear positive magnetic anomalies and magnetic anomaly gradient zones by slowly varying the background, negative magnetic anomaly field, which indicated the presence of strong magmatic activities in these regional deep faults; it also revealed the favorable areas of copper and polymetallic mineralization. This study provides some basic information for further research on the geology, structural characteristics, and mineral resource prospecting in northern Chile. 相似文献
20.
Current state of knowledge regarding South America wetlands and their future under global climate change 总被引：1，自引：0，他引：1
Wolfgang J. Junk 《Aquatic Sciences - Research Across Boundaries》2013,75(1):113-131
The exact size of the wetland area of South America is not known but may comprise as much as 20% of the sub-continent, with river floodplains and intermittent interfluvial wetlands as the most prominent types. A few wetland areas have been well studied, whereas little is known about others, including some that are very large. Despite the fact that most South American countries have signed the Ramsar convention, efforts to elaborate basic data have been insufficient, thereby hindering the formulation of a wetland-friendly policy allowing the sustainable management of these areas. Until now, the low population density in many wetland areas has provided a high level of protection; however, the pressure on wetland integrity is increasing, mainly as a result of land reclamation for agriculture and animal ranching, infrastructure building, pollution, mining activities, and the construction of hydroelectric power plants. The Intergovernmental Panel on Climate Change has predicted increasing temperatures, accelerated melting of the glaciers in Patagonia and the Andes, a rise in sea level of 20–60 cm, and an increase in extreme multiannual and short-term climate events (El Niño and La Niña, heavy rains and droughts, heat waves). Precipitation may decrease slightly near the Caribbean coast as well as over large parts of Brazil, Chile, and Patagonia, but increase in Colombia, Ecuador, and Peru, around the equator, and in southeastern South America. Of even greater impact may be a change in rainfall distribution, with precipitation increasing during the rainy season and decreasing during the dry season. There is no doubt that the predicted changes in global climate will strongly affect South American wetlands, mainly those with a low hydrologic buffer capacity. However, for the coming decades, wetland destruction by wetland-unfriendly development planning will by far outweigh the negative impacts of global climate change. South American governments must bear in mind that there are many benefits that wetlands bring about for the landscape and biodiversity as well as for humans. While water availability will be the key problem for the continent’s cities and agroindustries, intact wetlands can play a major role in storing water, buffering river and stream discharges, and recharging subterranean aquifers. 相似文献