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71.
L. Seeber O. Emre M.-H. Cormier C.C. Sorlien C.M.G. McHugh A. Polonia N. Ozer N. Cagatay The team of the R/V Urania Cruise in the Marmara Sea 《Tectonophysics》2004,391(1-4):239
Bends that locally violate plate-motion-parallel geometry are common structural elements of continental transform faults. We relate the vertical component of crustal motion in the western Marmara Sea region to the NNW-pointing 18° bend on the northern branch of the North Anatolian Fault (NAF-N) between the Ganos segment, which ruptured in 1912, and the central Marmara segment, a seismic gap. Crustal shortening and uplift on the transpressive west side of the bend results in the Ganos Mountain; crustal extension and subsidence on the transtensional east side produce the Tekirdağ Basin. We propose that this vertical component of deformation is controlled by oblique slip on the non-vertical north-dipping Ganos and Tekirdağ segments of the North Anatolian Fault. We compare Holocene with Quaternary structure across the bend using new and recently published data and conclude the following. First, bend-related vertical motion is occurring primarily north of the NAF-N. This suggests that this bend is fixed to the Anatolian side of the fault. Second, current deformation is consistent with an antisymmetric pattern centered at the bend, up on the west and down on the east. Accumulated deformation is shifted to the east along the right-lateral NAF-N, however, leading to locally opposite vertical components of long- and short-term motion. Uplift has started as far west as the landward extension of the Saros trough. Current subsidence is most intense close to the bend and to the Ganos Mountain, while the basin deepens gradually from the bend eastward for 28 km along the fault. The pattern of deformation is time-transgressive if referenced to the material, but is stable if referenced to the bend. The lag between motion and structure implies a 1.1–1.4 Ma age for the basin at current dextral slip rate (2.0–2.5 cm/year). Third, the Tekirdağ is an asymmetric basin progressively tilted down toward the NAF-N, which serves as the border fault. Progressive tilt suggests that the steep northward dip of the fault decreases with depth in a listric geometry at the scale of the upper crust and is consistent with reactivation of Paleogene suture-related thrust faults. Fourth, similar thrust-fault geometry west of the bend can account for the Ganos Mountain anticline/monocline as hanging-wall-block folding and back tilting. Oblique slip on a non-vertical master fault may accommodate transtension and transpression associated with other bends along the NAF and other continental transforms. 相似文献
72.
本文综合运用不同时代幔源包体平衡温压对比、玄武岩地球化学性质对岩石圈厚度的反演以及不同时代岩石圈地幔地球化学性质的对比的方法,把华北地块东部岩石圈的减薄时间限定在晚中生代至新生代之间。减薄的机制可能是华北东部地区晚白垩世以来大陆岩石圈的拉张作用。由于机械性拉薄和热、机械和化学侵蚀作用,岩石圈厚度最终减薄到70km以下。但古老的岩石圈地幔并没有完全因减薄而消失,残留部分受到了来自软流圈物质的强烈改造,使其Sr、Nd同位素组成类似于软流圈,但Os同位素没有受到明显的改变。改造后的岩石圈地幔成为华北地块东部新生代岩石圈地幔的主体。在时空上,岩石圈的减薄具有不均一的性质。 相似文献
73.
成熟勘探的矿集区非常有必要开展新一轮的找矿,但矿床模式的局限和大埋藏深度等困难制约了这些地区的预测性找矿发现。促进其预测性找矿发现的关键战略包括:勘查模型的创新、勘查技术的创新和各种信息的综合集成预测。勘查模型的创新必须包含基于地球动力学剖析的新成矿概念,动力学数值模拟是有效的创新手段之一;勘查技术创新的主要目的是加大探测深度和提高探测与解释的准确性,必须以详细可靠的地质资料为基础;综合信息集成是利用GIS和知识驱动及数据驱动的方法充分提取各种数据中的有用信息,集成为更加可靠的预测图。在这种思想的指导下,我们在铜陵凤凰山矿田进行了预测和勘查,并成功地发现了深部的隐伏矿床。 相似文献
74.
A numerical wave flume is constructed based on the Reynolds Averaged Navier-Stokes (RANS) equations with turbulence closure by a modified k-ε model to study the viscous interactions of waves with vertical breakwaters for different overtopping cases. The governing equations,the turbulence model,boundary conditions,and solution method for the numerical wave flume are introduced briefly. The reliability of the numerical wave flume is examined by comparing the numerical results with the experimental measurement... 相似文献
75.
本文介绍由重磁资料计算上海地区居里面、莫霍面、均衡重力异常及地幔流应力场的方法和成果,并在对成果初步分析的基础上,探讨了深部地质构造特征及其与地震活动趋势的关系,其中着重讨论了居里面及其与地震活动的关系。文章最后提出了对上海地区地震活动趋势的几点认识。 相似文献
76.
R.A. Duncan J. Backman L. Peterson The Shipboard Scientific Party 《Journal of Volcanology and Geothermal Research》1989,36(1-3)
Leg 115 of the Ocean Drilling Program recovered basaltic rocks from four sites along the ancient trail of the Réunion hotspot. The age of volcanism, determined from biostratigraphic data at the four sites, increases to the north and records the motion of India away from the Réunion hotspot through Tertiary time. Hotspot activity began with the eruption of the Deccan flood basalt flows at the time of the Cretaceous/Tertiary boundary. The Réunion hotspot has been stationary with respect to other hotspots in the Atlantic and Indian Ocean basins through Tertiary time. The geochemical compositions of the drilled basalts differ according to the relative contributions of magmas from hotspot and MORB mantle sources. 相似文献
77.
Zhang Guomin Geng Lumin and Shi YaolinCenter for Analysis Prediction Beijing China 'Graduate School Academia Sinica Beijing China 《中国地震研究》1995,(1)
Based on the study of activity of earthquakes with M**********>7.0 in mainland China,we have found a dynamic pattern,i.e.,the cyclic characteristics in time and migration from one seismic zone to another in space.In order to understand the physical mechanism of this pattern,we use a nonlinear dynamic model to simulate the seismic activity in fault zones under a unified tectonic stress field.The basic elements in our model consist of a Maxwell body and a rigid sliding block.Basic elements in a column represent a fault,and coupling elements connecting different columns simulate the interaction among faults and fault segments.The results provide insights to the cyclic activity of strong earthquakes and to the feature of mutual influence between strong earthquakes in groups in the climax of seismic activity. 相似文献
78.
空间数据仓库研究综述 总被引:7,自引:0,他引:7
论述了空间数据仓库的定义、基本特征;着重叙述了目前国内外空间数据仓库在学术研究、产品研制和实际应用方面的发展现状;设计出了空间数据仓库的体系结构,说明了空间数据仓库和应用系统的区别与联系;最后得出结论,为支持我国空间数据基础设施建设,研制空间数据仓库十分必要。 相似文献
79.
西太平洋海山磷酸盐的常量、微量和稀土元素地球化学研究 总被引:8,自引:0,他引:8
本文对主要取自于西太平洋我国调查区内不同海山、不同水深、不同产状的13个磷酸盐样品进行了常量、微量和稀土元素测定,以探讨与大洋富钴结壳密切伴生的磷酸盐的常、微量和稀土元素地球化学的特征。分析结果表明,调查区磷酸盐中主要氧化物的平均值与赤道太平洋的相近,暗示两者可能有相似的形成环境和形成机制。磷酸盐中微量元素Sr、Ba、Co、Cu、Ni及U丰度分别变化于862×10~(-6)~2181×10~(-6)、29×10~(-6)~3429×10~(-6)、6.3×10~(-6)~115×10~(-6)、23×10~(-6)~263×10~(-6)、12×10~(-6)~825×10~(-6)及4×10~(-6)~11×10~(-6),丰度多数低于泥质岩平均值,其CaO/P_2O_5、F/CO_2、Sr/P_2O_5值及常量、微量元素间的相关关系,清晰地显示了磷酸盐的种类、成分与结构、形成的地质背景和元素的主要组合特征。磷酸盐的稀土丰度为136.50×10~(-6)~853.70×10~(-6);Ce~*变化于0.01~0.18之间;(Ce/Yb)_N值变化于0.01~0.21之间。研究证实,不同产状磷酸盐的稀土元素配分模式基本一致,曲线相互平行,基本不呈现交叉现象,均呈Ce强烈亏损,轻、重稀土分馏程度大及重稀土富集的型式。调查区、赤道太平洋、中太平洋磷酸盐的稀土元素丰度、Ce~*、Ce/Yb值以及它们与海水稀土元素配分模式相似的特征,也进一步显 相似文献
80.
Researches on Plants from the Lower Devonian Xujiachong Formation in the Qujing District, Eastern Yunnan 总被引:1,自引:0,他引:1
WANG Deming HAO Shougang LIU Zhenfeng School of Earth Space Sciences Peking University Beijing 《《地质学报》英文版》2002,76(4):393-407
Fossil plants Hedeia sinica Hao et Gensel 1998, Huia gracilis Wang et Hao 2001 and Guangnania cuneata Wang et Hao are described from the Lower Devonian Xujiachong Formation, the Qujing district, eastern Yunnan, China. They contribute to our knowledge of the flora in this district. Based on the occurrence of common plants (Hedeia, Huia, Guangnania and Zosterophyllum australianum) and their horizons, it is proved for the first time that the mid-lower assemblage of the Xujiachong flora is comparable with the Early Devonian ((late) Pragian) Posongchong flora of southeastern Yunnan and the upper Baragwanathia flora of Australia. In view of this fact and the stratigraphic sequence, the mid-lower part of the Xujiachong Formation is considered to be of (late) Pragian age. Through comprehensive analyses of plant, bivalve and fish assemblages and the lithology, the upper part of the Xujiachong Formation is dated to be of early Emsian age. The Xujiachong flora belonged to the northeastern Gondwana palaeophytogeogr 相似文献