共查询到17条相似文献，搜索用时 218 毫秒
1.
海山等粗糙海底的俯冲对增生楔的结构、地貌、应力和地震灾害有着重要的影响。希库朗伊（Hikurangi）俯冲带位于新西兰北岛外海,希库朗伊高原向西正以40～47 mm/a的速率俯冲于澳大利亚板块之下。希库朗伊高原内部发育大量形态各异的海山,其俯冲造成希库朗伊北缘经历了严重的构造侵蚀。目前该区域的慢滑移事件有了很好的地震学和测地学约束,但对于希库朗伊北缘的构造侵蚀和构造应力体制如何演化以及对地震活动的影响仍然不清。本文基于离散元方法（DEM）数值模拟,结合地震反射剖面,探讨了海山俯冲对希库朗伊俯冲带北缘增生楔的形态、断裂结构、活动性、应变分配的影响。模拟结果显示海山的俯冲在其顶部形成一条巨型分支断层(mega-splay fault),吸收主要的缩短量并沿海底发生长距离、低角度逆冲推覆。随着俯冲的持续,海山前缘形成一个双重构造剪切带,而随着滑脱层的下移并向前扩展,最终形成前缘逆冲断裂体系。模拟证实海山俯冲提高了弧前增生楔内应力分布的非均质性,海山前缘最大剪切应力显著累积,而海山后缘则表现为一个稳定的应力影区。海山俯冲显著增加了希库朗伊俯冲带板间逆冲断层的几何粗糙度和物质非均质性,对微地震和... 相似文献
2.
《海洋地质与第四纪地质》2017,(2)
为确定南海西部的中—西沙地块是否存在前新生代地层与构造,对研究区内多道反射地震剖面资料进行了地层-构造解释,并结合围区钻井、拖网等岩石地层资料,在研究区北部发现了前新生代地层-构造变形形迹。运用回剥法、去断层恢复法和地质反序法对前新生代地层的构造变形进行了古恢复。结果表明,研究区的地层可划分为上、中、下三套构造层,其中属于前新生界的下构造层可见褶皱、逆冲等挤压构造样式,前新生代末期,其构造形态表现为一系列连续的宽缓褶皱,结合断层逆冲推覆方向可判断其主要挤压应力来自于东南方向,并推测该挤压作用与古南海的扩张有关。 相似文献
3.
经过对"探宝号"调查船在2001年8月在南海东北部陆坡及台湾南部恒春海脊海域采集的多道地震剖面资料进行的地震反射波数据分析、研究和解释,结果表明:(1)南海东北部陆坡段区域和台湾南部恒春海脊海域地震剖面上均显示有被作为天然气水合物存在标志的BSR,但两区域构造成因、形式和相关地质环境的不同造成了此两处的天然气水合物成因及过程的不同.(2)南海东北部陆坡区域的水合物形成与该区广泛发育的断裂带、滑塌构造体及其所形成的压力场屏蔽环境有关,而台湾南部恒春海脊海域的天然气水合物的形成则与马尼拉海沟俯冲带相关的逆冲推覆构造、增生楔等及其所对应的海底流体疏导体系有关.(3)南海陆缘区域广泛发育有各种断裂带、滑塌构造体、泥底辟、俯冲带、增生楔等,且温压环境合适,是天然气水合物矿藏极有可能广泛分布的区域. 相似文献
4.
台湾增生楔的构造单元划分及其变形特征 总被引：6，自引：0，他引：6
台湾增生楔位于欧亚板块、菲律宾海微板块和南海的结合部位,是现代弧陆碰撞研究的理想场所。通过对南海973航次在该区域的多道地震剖面的解释,对该增生楔进行了构造单元的划分,并分析了变形特征。认为台湾增生楔是由3个部分,即弧陆碰撞产生的增生部分、洋内俯冲产生的增生部分和增生楔后端在恒春海脊和北吕宋海槽之间的构造楔组成,研究区的高屏斜坡、恒春海脊和北吕宋海槽西端变形带分别是3个部分的反映。自中中新世以来,南海洋壳开始沿着马尼拉海沟向菲律宾海微板块俯冲,形成增生楔中洋内俯冲增生部分;与此同时菲律宾海微板块开始向NW方向移动,前缘的吕宋岛弧自6．5Ma B．P以来与亚洲陆缘斜向碰撞,形成增生楔中弧陆碰撞增生部分。碰撞首先发生在台湾岛的北部,由于弧陆强烈的挤压作用,增生楔后端部分向北吕宋海槽倒冲楔人,使得上部的北吕宋海槽的沉积发生隆升变形。滨海的各个地貌单元可以和台湾陆上的地貌单元相联系,它们具有相似的地质特征,但是由于陆上部分增生历史久,不仅抬升为陆,而且地层的年代也更老。 相似文献
5.
褶皱调节断裂是一种在褶皱发育过程中形成的、与构造和地层位置有关的、调节应力变化的二级断裂。最常见的褶皱调节断裂有四种类型。伸出向斜的逆冲断裂和进入背斜的逆冲断裂主要是由褶皱核部不断增加的地层曲率所引起的，虽然层面方向不同级别的差异应力也影响了断裂的断距。根据主要褶皱动力学演化机制的不同，这些逆冲断裂可以沿不对称褶皱的陡翼或缓翼延伸，也可以沿对称褶皱的枢纽延伸。楔状逆冲断裂主要是由于刚性地层中相邻地层之间层面方向的刺穿应力变化而形成的。翼部楔主要表现为断弯褶皱或断倾褶皱的上盘和，或下盘，而枢纽楔则主要表现为趋于加厚刚性较强的地层的多重嵌套断裂。前翼逆冲断裂和后翼逆冲断裂具有一系列的形成机制。前翼空间调节逆冲断裂是一种断距较小的逆冲断裂，它所调节的是由褶皱核部不断增加的地层曲率所引起的应力不连续性。前翼切变逆冲断裂形成于褶皱作用的晚期，主要成因是褶皱陡倾前翼的地层旋转和平行于层面的拉张作用。大多数的后翼逆冲断裂均起源于伸出向斜的逆冲断裂。最终，这些断裂还可以与前翼逆冲断裂一起组成前翼-后翼逆冲断裂。背冲断裂所调节的是断裂相关褶皱形成过程中的上盘应力，它们可以形成于刚性地层之中，还可以以主逆冲断裂的发育速度穿过地层。虽然褶皱调节断裂是一种二级构造，但是，它们却是确定褶皱-逆冲断裂构造中构造圈闭的几何形态及规模的重要因素。因此，在解释褶皱和逆冲断裂带的构造几何形态时，对这些构造进行的准确成图将是非常关键的。 相似文献
6.
7.
菲律宾海板块沿台湾岛和吕宋岛之间东倾的马尼拉海沟向欧亚板块仰冲。板块汇聚边缘自南而北逐渐由南海岩石圈的正常俯冲过渡到台湾造山带的初始碰撞。与俯冲相关的地震遍及台湾附近，往台湾方向增生体急剧增宽。为了认识这种以俯冲一碰撞转换带为特征的汇聚板块边缘，我们分析了12条位于吕宋岛与台湾岛之间横切马尼拉海沟的地震反射剖面。结果显示，南海海盆北部基底通常向东和向南倾。在马尼拉海沟北段，海沟充填沉积物南部比北部多，t0层序界面是近海沉积与海沟充填沉积物的界面。可能由于台湾地区的碰撞作用，t0层序北部坡度更平缓或者被抬升。构造分析显示，马尼拉海沟北段俯冲地壳具有三个特征带：正断层带（NFZ）、原始逆冲带（PTZ）和逆冲带（TZ）。正断层带主要由俯冲地壳顶部或上部的一系列正断层组成，在接近深海沟的部位，这些正断层逐渐被海沟充填沉积物所覆盖，暗示正断层带发生在地壳开始弯曲、并引起上部沉积层重力变化的地方。由于增生体附近板块边缘强烈的汇聚作用，一些被埋藏的正断层而被活化为隐伏逆冲断层。原始逆冲带位于正断层带和增生体的前缘逆冲带之间，含隐伏的逆冲断层或者褶皱而不是逆冲断层。海沟区正断层、隐伏逆冲断层和逆冲断层在地壳结构中的连续分布，指示隐伏逆冲断层是沿着之前拉张正断层的位置发育的。上部沉积层的脆性变形很可能是强烈的挤压作用和水分较少的原因所致，最终隐伏逆冲断层可能向上发展，成为海底逆冲断层。 相似文献
8.
南海东北部陆坡与恒春海脊天然气水合物分布的地震反射特征对比 总被引：3，自引：0，他引：3
对“探宝号”调查船2001年8月在南海东北部陆坡及台湾南部恒春海脊海域采集的多道地震剖面资料进行了地震反射波数据分析、解释和研究,并对南海北部陆坡、陆隆及其东侧俯冲带等区域天然气水合物矿藏的成藏规律及分布特征作了初步的分析与探讨,结果表明:(1)南海东北部陆坡和台湾南部恒春海脊海域地震剖面上均显示有BSR,但两区域构造成因、形式和相关地质环境的不同造成了天然气水合物的成因及过程不同。(2)南海东北部陆坡区域的天然气水合物形成与该区广泛发育的断裂带、滑塌构造体及其所形成的压力场屏蔽环境有关,而台湾南部恒春海脊海域天然气水合物的形成则与马尼拉海沟俯冲带相关的逆冲推覆构造、增生楔及其所对应的海底流体疏导体系有关。(3)南海陆缘区域广泛发育有各种断裂带、滑塌构造体、泥底辟、俯冲带、增生楔等,且温压环境合适,是天然气水合物矿藏极有可能广泛分布的区域。 相似文献
9.
10.
印支运动为现今渤海海域构造格局的形成奠定了基础,导致渤海海域内部发育3个主要逆冲带。渤海基底内部的先存断层与滑脱层在此过程中可能起到了极为重要的作用,但其如何影响渤海海域印支期的构造变形与分带特征的机制尚不清楚。为了解决上述问题,本文基于地震剖面数据,结合二维热力学数值模拟代码LaMEM对渤海海域印支期的构造变形展开了详细研究。模拟结果揭示,在先存断层存在的条件下,当基底内部无滑脱层或未呈阶梯式在渤海海域分布时,渤海海域内部不会形成相应的逆冲中心;而当基底内部的滑脱层呈阶梯状分布在渤海海域西南部、渤中坳陷以及辽东坳陷3个区域时,应力通过滑脱层在基底内部进行传导,使海域形成了3个逆冲中心,并导致渤海内部大规模的逆冲断层与褶皱变形的发育,与地震剖面具有较好的一致性。数值模拟实验结果证实,基底内部的先存断层与滑脱层是控制渤海海域构造分带性及构造变形特征的重要因素。同时,多逆冲中心演化模式也为解释现今龙门山和四川盆地的形成与演化过程提供了重要的借鉴。 相似文献
11.
Crustal structure and deformation associated with seamount subduction at the north Manila Trench represented by analog and gravity modeling 总被引：1，自引：0，他引：1
We investigated the deformation in the accretionary wedge associated with subducted seamounts in the northern Manila Trench by combining observations from seismic profiles and results from laboratory sandbox experiments. From three seismic reflection profiles oriented approximately perpendicular to the trench, we observed apparent variations in structural deformation along the trench. A number of back-thrust faults were formed in the accretionary wedge where subducted seamounts were identified. In contrast, observable back-thrusts were quite rare along the profile without seamounts, indicating that seamount subduction played an important role in deformation of the accretionary wedge. We then conducted laboratory sandbox experiments to investigate the effects of subducted seamounts on the structural deformation of the accretionary wedge. From the analog modeling results we found that seamount subduction could cause well-developed back-thrusts, gravitational collapse, and micro-fractures in the wedge. We also found that a seamount may induce normal faults in the wedge and that normal faults may be eroded by subsequent seamount subduction. In addition, we constrained the crustal structure of the South China Sea plate from modeling free-air gravity data. The dip angle of the subducting plate, which was constrained by hypocenters of available earthquakes, increased from south to north in the northern Manila Trench. We found a laterally heterogeneous density distribution of the oceanic crust according to the gravity data. The density of subducted crust is ~2.92 g/cm3, larger than that of the South China Sea crust (2.88 g/cm3). 相似文献
12.
南沙海槽南缘逆掩推复构造地区的动力学分析 总被引：1，自引：1，他引：1
提出南沙海槽南缘推复构造的运动和形变是一种周期性的弹塑性运动,周期约为14Ma.建立推复楔形体的动力学模型及两个约束条件,求解得推复楔形体的底部中点的推复方向的主应力和逆掩面动摩擦系数的解析式.建立推复楔形体前缘地层被推复剪断的力学模型、密度模型和内摩擦角模型,求得推复前缘地层被推复剪断时的有效主应力、静岩压应力、推复方向的主应力及其合力和推复构造应力的解析式,建立推复底部的有效塑性屈服模型,求得推复底部屈服时中点的有效主应力和推复方向的主应力的解析式.选择两个剖面进行动力学计算,得到推复楔形体前缘的两个应力图、逆掩面的动摩擦系数及推复方向的主应力的合力. 相似文献
13.
Junjiang Zhu Zongxun Sun Heidrun Kopp Xuelin Qiu Huilong Xu Sanzhong Li Wenhuan Zhan 《Marine Geophysical Researches》2013,34(3-4):379-391
Based on bathymetric data and multichannel seismic data, the Manila subduction system is divided into three segments, the North Luzon segment, the seamount chain segment and the West Luzon segment starts in Southwest Taiwan and runs as far as Mindoro. The volume variations of the accretionary prism, the forearc slope angle, taper angle variations support the segmentation of the Manila subduction system. The accretionary prism is composed of the outer wedge and the inner wedge separated by the slope break. The backstop structure and a 0.5–1 km thick subduction channel are interpreted in the seismic Line 973 located in the northeastern South China Sea. The clear décollement horizon reveals the oceanic sediment has been subducted beneath the accretionary prism. A number of splay faults occur in the active outer wedge. Taper angles vary from 8.0° ± 1° in the North Luzon segment, 9.9° ± 1° in the seamount segment to 11° ± 1° in the West Luzon segment. Based on variations between the taper angle and orthogonal convergence rates in the world continental margins and comparison between our results and the global compilation, different segments of the Manila subduction system fit well the global pattern. It suggests that subduction accretion dominates the north Luzon and seamount chain segment, but the steep slope indicates in the West Luzon segment and implies that tectonic erosion could dominate the West Luzon segment. 相似文献
14.
Deep water fold and thrust belts (DWFTBs) are sedimentary wedges that accommodate plate-scale deformation on both active and passive continental margins. Internally, these wedges consist of individual structures that strongly influence sediment dispersal, bathymetry and fluid migration. Most DWFTB studies investigate basin- and intra-wedge- scale processes using seismic reflection profiles, yet are inherently limited by seismic resolution. Of critical importance is strain distribution and its accommodation on discrete faults compared to distributed deformation. Recent studies have considered strain distribution by investigating regional reflection DWFTBs profiles within coupled systems, which contain down-dip compression and up-dip extension. There is broad agreement of a mis-balance in compression versus extension, with ∼5% excess in the latter associated with horizontal compaction, yet this remains unproven.Using two exceptionally well exposed outcrops in the Spanish Pyrenees we consider deformation of DWFTB at a scale comparable to, and beyond, seismic resolution for the first time. By coupling outcrop observations (decametre to hectometre scale) with a re-evaluation of seismic profiles from the Orange Basin, South Africa, which contains one of the best imaged DWFTBs globally, we provide a unique insight into the deformation from metre to margin scale. Our observations reveal hitherto unrecognised second order structures that account for the majority of the previously recognised missing strain. This re-evaluation implies that ∼5% missing strain should be accounted for in all DWFTBs, therefore existing studies using restorations of the sediment wedge will have underestimated crustal shortening in active margins, or sedimentary shortening in gravity driven systems by this amount. In contrast to previous studies, our observations imply that the majority of this strain is accommodated on discrete fault surfaces and this can explain the occurrence and location of a range of intra-wedge processes that are intimately linked to structures including sediment dispersal, fluid migration pathways and reservoir compartmentalisation. 相似文献
15.
16.
Ho-Shing Yu 《Marine Geophysical Researches》2004,25(1-2):109-122
Marine seismic reflection profiles from offshore SW Taiwan combined with onland geological data are used to investigate the distribution and nature of the deformation front west of Taiwan. Locations of the frontal structure west of Taiwan are generally connected in a linear fashion, although the alignment of frontal structures is offset by strike-slip faults. The deformation front begins from the northern Manila Trench near 21°N and continues northward along the course of the Penghu Submarine Canyon in a nearly N–S direction north of 21°N until it reaches the upper reaches of Penghu Canyon at about 22°15′N. The deformation front then changes direction sharply to the northeast. It connects to the Chungchou thrust fault or the Tainan anticline in the coastal plain and continues northwards along the outer Western Foothills to the northern coast of Taiwan near 25°N. Characteristics of structural style, strain regime, sedimentation and tectonics vary along the trend of the deformation front. Ramp anticlines, diapiric intrusion and incipient thrust faults are commonly associated with the deformation front. Variations in structural style along strike can be related to different stages of oblique collision in Taiwan. The deformation front (collision front) west of Taiwan can be considered as a boundary between contraction in the Taiwan orogen and extension west of the collision zone. The deformation front east of the Tainan Basin and its northward extension along the outer limit of the Western Foothills is the surface trace separating the foreland thrust belt from the nearby foredeep, not a boundary between the Chinese and Taiwan margins. The submarine deformation front off SW Taiwan is the surface trace separating the submerged Taiwan orogenic wedge from the Chinese passive continental margin, not a surface trace of the plate boundary between the Eurasian and Philippine Sea plates. 相似文献
17.
The accumulation mechanism of methane hydrates has been a central issue in previous hydrate research regarding the Nankai accretionary prism, southwest of Japan. Expulsion of formation fluids is significant during the prism accretion process, and the migration of these methane-bearing fluids exerts a strong control on the accumulation of hydrates. Two types of fluid pathways, inter-granular porosity and faults, need to be evaluated to understand hydrate accumulation. Fluid migration along faults can be partly modeled by examining faulting activity. Our study modeled the accretion process by using two granular methods that approximated the geologic body as an assemblage of particles: (1) analog experiments using granular materials, and (2) a numerical simulation based on the distinct element method. The analog experiments closely reproduced the prism geometry observed in seismic profiles across the Nankai accretionary prism. Digital image correlation analysis indicated that the frontal thrust is generally active but older structures are also frequently reactivated. The numerical simulations produced prism geometries similar to those of the analog experiments. The velocity distributions of the particles showed evidence of episodic faulting and reactivation, but the internal stress field exhibited little change in the deeper part of the prism during deformation. The frequent and substantial changes in fault activity displayed by the models indicate episodic fluid flow along fault surfaces. Active frontal thrusting suggests that formation fluids generally migrate from deep within the prism to the deformation front, but may move along reactivated older faults. Inter-granular permeability also fluctuates, as it is controlled by temporal and spatial variations in the internal stress field. However, fluid flow is likely to be relatively stable in the deeper segment of the prism. 相似文献