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Using methods of discontinuous deformation analysis and finite element (DDA+FEM), this paper simulates dynamic processes of the Tangshan earthquake of 1976, which occurred in the northern North China where its internal blocks apparently interacted. Studies focus upon both the movement and deformation of the blocks, in particular, the Ordos block, and variations of stress states on the boundary faults. The Tangshan earthquake was composed of three events: slipping motions of NNE-striking major fault, NE-striking fault near the northeastern end of the NNE-striking fault, and NW-striking fault on the southeastern side of the NNE-striking fault. Compared with previous studies, our model yields a result that is more agreeable with the configuration of aftershock distributions. A number of data are presented, such as the principle stress field during the earthquake, contours of the maximum shear stress, the strike-slip deformation between blocks near the earthquake focus, time-dependent variations of slips of earthquake-triggered faulting, the maximum slip distance, and stress drops. These results are in accord with the earthquake source mechanism, basic parameters from earthquake wave study, macro-isoseismic line, observed horizontal displacement vectors, etc. The Tangshan earthquake exerted different influences on the adjacent blocks and boundary faults between them, thus resulting in differential movement and deformation. The Ordos block seems to have experienced the small-scale counterclockwise rotation and deformation, but its northeast part, bounded on the east by the Taihangshan and on the north by the Yanshan and Yinshan belts, underwent relatively stronger deformation. The Tangshan earthquake also changed the stress state of boundary faults of the North China, leading to an increase in shear stress and a decrease in normal stress in the NW-trending Zhangjiakou-Penglai fault through Tangshan City and the northern border faults of the Ordos block, and therefore raises the potential risk of earthquake occurrence. This result is supported by the facts that a series of Ms≥ 6 earthquakes took place at the northern margin of the Ordos block after the Tangshan earthquake. 相似文献
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华北板块与扬子板块于加里东晚期沿商丹带发生碰撞的同时,在扬子板块北缘,即现今南秦岭构造带,开始发育一条近东西向延伸的拉伸带,其中包括武当地块伸展滑脱构造、武当地块古生代大规模基性岩浆活动及其西侧紫阳-岚皋古生代碱性岩浆活动带、镇安-旬阳浅层塌陷盆地以及佛坪隆起等.该伸展构造带主体在时间上发生在秦岭两期碰撞事件之间,空间上位于南北两个缝合带之间,因此,是秦岭造山带演化过程中的一个非常重要的阶段.该伸展构造的开始很可能与南、北秦岭碰撞后的造山带重力塌陷有关,随着该伸展带南侧晚古生代勉略洋的形成,南秦岭逐渐演化为华北板块南侧的被动大陆边缘,从而使南秦岭的地壳伸展一直延续到早一中三叠世.武当地块伸展滑脱系统中顺层侵位的基性岩席群的年代学与岩石地球化学的研究表明,这些基性岩与勉略蛇绿岩组合中的变辉绿岩及变基性火山岩具有很大的相似性,因此勉略洋很可能也是南秦岭这次拉伸作用的结果. 相似文献
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氢能够显著地影响岩石的物理性质,如岩石的流变等.它能赋存于通常不含水的矿物中,如上地幔的橄榄石.为了解上地幔的物理性质和地球化学过程,测量氢在橄榄石中的溶解度是非常重要的.在 相似文献
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Impedance spectroscopy analysis on electrical properties of serpentine at high pressure and high temperature 总被引:1,自引:0,他引:1
The electrical conductivity of serpentine is measured and the microscopic conductance mechanisms are investigated with impedance
spectroscopy at 2.5–4.0 GPa and 220–780°C. The results show that the electrical conductivity is strongly dependent on the
frequencies used, and that only arc I, which reflects grain interior conductance, occurs and dominates the whole conductance
processes over 12-105Hz at high pressure before dehydration. The arc II, which indicates the grain boundary process, begins to occur at the initial
stage of dehydration. After dehydration, due to the presence of highly conductive networks of free water, the electrical conductivity
is not dependent on frequencies any longer and the total electrical conductivity is dominated by process of ionic conductance
of free water in interconnected networks. Dehydration of serpentine enhances pronouncedly the total electrical conductivity,
through which highly conductive layers (HCL) may be formed in the earth’s interior. 相似文献
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