我国大陆及其邻区6级以上地震的“缺震事件”——一种大地震中期预测指标的分析研究   总被引：1，自引：0，他引：1  

黄圣睦 《内陆地震》1991,(3)

在内陆强震活动的起伏中,6级以上地震的大范围长时间缺震,具有重要的意义。有的研究者已将其作为将发生7级地震前的标志之一。作者系统地清理了1897—1988年8月间中国大陆及其邻区6级以上地震“缺震事件”的始末,较多的震例表明,限定“缺震事件”起止的地震具有中期预报意义。它们在地震构造上的原因可能是代表区域最活跃的破裂,突然处于阻碍、闭锁状态,其持续时间大于10个月,再次发生6级以上地震为解锁,并随即出现新的一轮大地震活动。故可以作为一种大地震中期预测的指标。  相似文献   

华北大陆地壳─上地幔岩石学结构与演化     

吴宗絮  邓晋福  赵海玲  杨主恩  罗淑兰 《岩石矿物学杂志》1994,(2)

本文基于出露的前寒武纪变质岩系、中、新生代岩浆活动以及新生代玄武岩中上地幔包体的岩石学与地质压力计研究，结合地球物理测涤资料与高温高压下岩石中地震波传播速度的实验成果，提出了华北大陆三个地区（河北平原、太行－五台、鄂尔多斯）的地壳－上地幔岩石学结构，讨论了界面性质及其演化。在强调ｖ＿ｐ、ｖｂ、σ结构与岩石学结构共同约束的基础上，有效地识别了不同地区硅铝质陆壳在物质组成上的差异和上地幔低速层或矿物相转变等特征。本文提出壳－幔岩石学结构及其演化，密切地与陆壳主要形成时期的太古－早元古构造岩浆事件相关，又与显生宙构造岩浆事件对它的改造程度有关，壳－幔岩石学结构是我们追索大陆的构造性质及其演化的一个重要记录和科学依据。  相似文献   

陆内碰撞体制流体作用及成矿作用研究的意义和现状   总被引：11，自引：0，他引：11  

陈衍景  于方 《地球科学进展》1995,10(4):318-322

陆内碰撞作用和流体作用都是８０年代以来的研究前沿，它们的研究必然会大大促进成矿作用研究的发展，也是跟踪和超越世界地球科学先进水平的重要途径。中国拥有最多最复杂的陆内碰撞带，为中国学者开发有关研究并取得高水平成果提供了得天独厚的条件。对陆内碰撞、流体作用和成矿作用研究现状的分析表明，三者之间研究的相互结合是薄弱环节，限制了有关问题的深入，但为我国学者开发该方向的研究，取得领先于国家水平的成果，提供了  相似文献   

由台湾海峡7．3级地震分析中国地震大形势     

刁守中 《高原地震》1995,(2)

本文论述了１９９４年９月１６日台湾海峡７．３级地震对中国地震大趋势所产生的可能影响。作者认为，这次地震应属于中国大陆板内地震，它可能标志着中国大陆及边邻地区７级以上地震从本世纪以来第五活动期（起始于１９８８年）的相对平静时段转入活跃时段并可能步入高潮。它打破了近十年来中国大陆７级地震只分布于青藏块体的格局，但并不意味着本期主体活动区（青藏块体及边邻）的改变；同时，这次地震标志着东南沿海地区进入新的地震活跃幕；台湾地区７级地震活动也将增强。  相似文献   

Geomorphological study on a clastic accretionary prism: The Nankai Trough     

Kyoko  Okino Yukihiro  Kato 《Island Arc》1995,4(3):182-198

Abstract The Nankai Trough, off southwest Japan, is one of the best sites for the study of geomorphic characteristics of a clastic accretionary prism. A recent multibeam survey over the central and eastern parts of the Nankai accretionary prism has revealed a large variation of the topography along the trough axis. Analysis of the bathymetric data suggests the existence of prism deformational features of different scales, such as depressions, embayment structures and cusps. These structures are the results of slope instability caused by basement relief of subducted oceanic plate. Unstable slopes recover by new accretion and development of a low angle thrust. Small-scale deformation due to the subduction of a small isolated seamount is then adjusted to the regional trend. By contrast, a 30 km indentation of the wedge observed in the eastern part of the Nankai Trough, the Tenryu Cusp, has seemed to retain its geometry. The subducted Philippine Sea plate has deformed greatly near the eastern end of the Nankai Trough, because of the collision between the Izu-Ogasawara (Bonin) arc and central Japan. Therefore, the indentation may be the result of the continuous subduction of a basement high, such as the Zenisu Ridge, which has been formed under north-south compression due to the arc-arc collision.  相似文献   

The Collision Manifold of the Collinear One-Bumper Two-Body Problem     

Samuel R. Kaplan 《Celestial Mechanics and Dynamical Astronomy》2001,79(1):1-14

We present a special model which is a caricature of the collinear three-body problem. Near triple-collision behavior for the model is governed by the collision manifold. We study the bifurcations of the dynamics on this manifold as we vary the ratio of masses. Both analytic and numerical results are presented.This revised version was published online in October 2005 with corrections to the Cover Date.  相似文献   

Simulations of strong ground motion in SW Iberia for the 1969 February 28 (M_s= 8.0) and the 1755 November 1 (M∼ 8.5) earthquakes – II. Strong ground motion simulations     

Raphaël Grandin  José Fernando Borges  Mourad Bezzeghoud  Bento Caldeira  Fernando Carrilho 《Geophysical Journal International》2007,171(2):807-822

This is the second paper of a series of two concerning strong ground motion in SW Iberia due to earthquakes originating from the adjacent Atlantic area. The aim of this paper is to use the velocity model that was proposed and validated in the companion paper for seismic intensity modelling of the 1969 ( M _s= 8.0) and 1755 ( M = 8.5–8.7) earthquakes.
First, we propose a regression to convert simulated values of Peak Ground Velocity (PGV) into Modified Mercalli Intensity (MMI) in SW Iberia, and using this regression, we build synthetic isoseismal maps for a large ( M _s= 8.0) earthquake that occurred in 1969. Based on information on the seismic source provided by various authors, we show that the velocity model effectively reproduces macroseismic observations in the whole region. We also confirm that seismic intensity distribution is very sensitive to a small number of source parameters: rupture directivity, fault strike and fault dimensions. Then, we extrapolate the method to the case of the great ( M = 8.5–8.7) 1755 earthquake, for a series of hypotheses recently proposed by three authors about the location of the epicentral region. The model involving a subduction-related rupture in the Gulf of Cádiz results in excessive ground motion in northern Morocco, suggesting that the source of the 1755 earthquake should be located further west. A rupture along the western coast of Portugal, compatible with an activation of the passive western Iberian margin, would imply a relatively low average slip, which, alone, would could not account for the large tsunami observed in the whole northern Atlantic ocean. A seismic source located below the Gorringe Bank seems the most likely since it is more efficient in reproducing the distribution of high intensities in SW Iberia due to the 1755 earthquake.  相似文献   

Upper mantle beneath foothills of the western Himalaya: subducted lithospheric slab or a keel of the Indian shield?   总被引：1，自引：0，他引：1  

L. Vinnik  A. Singh  S. Kiselev  M. Ravi Kumar 《Geophysical Journal International》2007,171(3):1162-1171

  相似文献   

发展中的板块边界:天山-贝加尔活动构造带   总被引：5，自引：1，他引：5  

冯锐  马宗晋  方剑  吴宣 《地学前缘》2007,14(4):1-17

亚洲内陆的强地震密集地发生在天山-贝加尔一线,但该处并不存在一条连续的大断裂,学术界对这个问题的认识长期相左。文中分析了这条地震带的时空分布、分区特点、应力状态和活动周期,计算了欧亚大陆的布格重力异常场、均衡重力异常场,反演了上地幔的密度分布和剪切波速分布。发现在这个部位的70~250km的深部有一条北东向的密度、速度陡变带,它是新生代的冷地幔和热地幔的交界带,与浅部构造存在立交关系,对亚洲大陆的现今构造运动和应力场具有重要的控制作用。这个带的地震不同于传统意义上的板缘地震和板内地震,是一种因为深浅构造不同而造成的结构性地震,性质上为大陆内缘地震。文中还就深浅构造的空间立交关系、时间镜像关系进行了讨论,指出在南北地震带和伊朗东侧地震带的立交结构也与上地幔构造有关。天山-贝加尔活动构造带是正在发展中的板块边界,是大陆内部的一个典型构造,北侧为稳定的俄罗斯-西伯利亚次板块,南侧为活动的中国-东南亚次板块。  相似文献   

Comparison of element abundance between the exposed crust of the continent of China and the global averaged upper continental crust: Constraints on crustal evolution and some speculations     

Wang Yang 《Frontiers of Earth Science》2007,1(1):69-79

Based on the results of a study of regional element abundance in eastern China and the 1:200 000 geochemical surveys in northern Xinjiang, the element geochemical characteristics of the exposed crust in 23 tectonic units of the continent of China are summarized. Compared with the global average abundance of the upper continental crust, the exposed crust of the continent of China is compositionally more evolved than the upper crust of the island arc, but less evolved than the mature Precambrian Canadian shield. The exposed crust of the North China and Yangtze platforms has a lower SiO₂ content, but markedly higher CaO and MgO contents due to the presence of widespread carbonate strata, which suggests that we should not neglect the contribution of carbonate rocks in the study of the exposed crust and the element abundance of the upper crust. In comparison with two recently published average compositional models of the global upper continental crust, the exposed crust of the continent of China is depleted in Au, Hg, Mo, Sn, and W, which suggests that their abundance in the present global models is overestimated. The exposed crust of the North China platform and the Qinling-Dabieshan fold belt to its south has lower μ(²³⁸U/²⁰⁴Pb) values (<8), but other regions of the continent of China exhibit much higher μ values, which implies that the low μ feature of the North China platform and its adjacent regions does not have global significance. Considering the apparent lateral variation in composition of the exposed crust for the tectonic units of the continent of China, there is no adequate reason to take the average upper crust compositional model of the North China platform and its adjacent regions as a reliable composition representative for Chinese and global upper continental crust composition. Translated from Geological Bulletin of China, 2005, 24(10–11): 906–915 [译自: 地质通报]  相似文献