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We used two-dimensional finite element models to explore different configurations of weak layers in undeformed sedimentary sequences to investigate the occurrence of three characteristic types of thrust configurations: ramp-flat; imbricate; and duplex. In our models, we embedded two low-friction weak layers with a finite spatial extent in a sequence of stronger rock. These two weak layers were initially horizontal, were separated vertically by 1 km, and were arranged in three different relative positions to each other. When the models were deformed and these weak layers developed into décollements, they interacted to produce one of the three types of thrust faults as a function of their initial configurations. When the tips of weak layers were separated by a large gap (>10 km), only the lower-level décollement became active, producing imbricate thrusts. When the two weak layers overlapped for a large distance (>10 km), they simultaneously became active décollements, producing duplexes in the overlapped zone. When the gap or overlap was small (<5 km), the two weak layers also simultaneously became active décollements but their tips linked up to form a ramp-flat geometry. These results suggest that thrust geometry is highly sensitive to the initial arrangement of décollements. 相似文献
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Dominique Frizon de Lamotte Jean-Claude Guézou Marie-Anne Albertini 《Geodinamica Acta》2013,26(4):267-281
AbstractThe Cenozoic westward motion of the Betic-Rif internal zone (“Alboran block”) between Iberia and Africa is constrained by paleogeographic considerations and by wrench faulting which affects both sides of the external zones. However, in the Alboran domain itself there was so far no evidence of significant internal deformation related to this westward displacement which was consequently consider as an en bloc” motion. Our work, in Eastern Andalucia, demonstrates that the main tectonic units building up the Betic zone should be regarded as large-scale tectonic sheets with a typical duplex style. The direction of the tectonic transport is to the West. At meso-scale, the major structures exhibit a combination of hindward and foreward dipping imbricates on the respective east and west sides of antiformal stacks or “rigid cores”. On a broader scale, the same geometric framework appears on both east and west sides of the Sierra Nevada window which we interpret as a tectonic culmination on the hangingwall of a Subbetic décollement zone. The development of this tectonics, in retrogressive metamorphic conditions, postdates the ductile deformation of the internal complexes. The morpho-tectonic relationships between the culmination of the metamorphic cores and the Neogene basins give a way to date the westward motion of the “Alboran System of Nappes” of the middle and upper Miocene. 相似文献
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以浙西北为例,基于上二叠统长兴组(P2c)和大隆组(P2d)以及下三叠统政棠组(T1z)深水浊积岩的发现,初步认为该区古生代至早三叠世具被动大陆边缘沉积楔特征。综合大地构造分析进一步表明研究区构造样式总体上以向北西逆冲的冲褶席(duplex)为特征,构造变形强度和密度自南东向北西呈递减趋势。自南东向北西具明显的分带性。该区大地构造相主要为前陆褶皱冲断带相,而上三叠统乌灶组(T3w)为前陆磨拉石盆地相,二者可能是该区始于早中生代(T1—T3)造山作用的响应。大地构造相分析不仅较为圆满地解释了研究区的众多地质现象,为造山带模式提供新的制约,而且能为研究区提出新的战略目标。 相似文献
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The Marathon portion of the Ouachita thrust belt consists of a highly deformed allochthonous wedge of Cambrian-Pennsylvanian slope strata (Marathon facies) that was transported to the northwest and emplaced over Pennsylvanian foredeep sediments. The foredeep strata in turn overlie early-middle Paleozoic shelfal sediments which are deformed by late Paleozoic basement-involved reverse faults. The Dugout Creek thrust is the basal thrust of the allochthon. Shortening in this sheet and overlying sheets is 80%. Steep imbricate faults link the Dugout Creek thrust to upper level detachments forming complex duplex zones. Progressive thrusting and shortening within the allochthon folded the upper level detachments and associated thrust sheets. The Caballos Novaculite is the most competent unit within the Marathon facies and controlled development of prominent detachment folds.Deeper imbricate sheets composed of the Late Pennsylvanian foredeep strata, and possibly early-middle Paleozoic shelfal sediments developed concurrently with emplacement of the Marathon allochthon and folded the overlying allochthon. Following termination of thrusting in the earliest Permian, subsidence and deposition shifted northward to the Delaware, Midland and Val Verde foreland basins. 相似文献
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针对汶川8.0级地震的主破裂面是否以陡立倾角延伸至地壳深部的争议,我们的研究旨在明确发震断层形态随深度分布的二维结构特征, 即断层的倾角及相应段落的深度, 并在此基础上分析发震断层的孕震和发震机理. 利用子空间置信域非线性反演方法, 通过拟合近场的同震水准变形, 获得了分别对应于清平-北川和南坝-青川发震断层的二维弹性位错模型. 结果显示, 此次龙门山中央断裂带的发震断层系统存在明显的南北分区特征. 以北川-南坝为过渡带, 北川以南至清平的发震构造为二元结构, 包括两部分:一是浅部高倾角的逆断层, 倾角在70°~80°以上, 底部深度可达10~15 km, 同震位错主要发生在10 km以上深度, 平均位错超过6 m;二是深部缓倾角的逆断层, 反演得其倾角约25°, 底部可达30 km深度, 位错主要分布于断层的顶部和底部, 平均位错约4 m. 南坝以北的发震断层为单一结构的逆断层, 倾角约60°~70°, 逆断层位错分布于10 km深度以上, 平均位错小于2 m.余震分布和主震震源机制也支持清平以南发震断层为二元结构的推论. 有限元模拟显示,在二元结构的逆断层系统中, 通过提高断层面上正的库仑应力, 深部缓倾角的逆断层活动对浅部高倾角逆断层有明显的促震作用. 模拟还显示地壳缩短不是现今松潘地块地表垂直变形的主要原因, 垂直变形更可能反映了青藏高原东缘相对四川盆地的差异抬升. 对高倾角逆断层的库仑应力作用显示, 差异抬升对龙门山逆断层活动有重要的促进作用. 相似文献