共查询到18条相似文献，搜索用时 125 毫秒
1.
《地球物理学报》2020,(9)
对于羌塘盆地是否存在横贯东西的中央隆起带,目前学术界仍有分歧.本文提供的最新高精度航空重、磁资料证实存在呈东西向贯通羌塘盆地的中央隆起带,并对该带的构造特征进行了精细刻画.隆起带受南北两侧深大断裂控制,其空间跨度(宽度)由西向东逐渐收敛,并被一组近南北向的隐伏断裂系切割、左滑错动.重、磁场资料还显示中央隆起带在双湖东、西两侧存在明显差异:西段基底大规模隆起,基岩深度一般在3～5 km以内,明显浅于南北羌塘坳陷7～15 km的基底埋深;东段基底隆起幅度明显降低,主要表现为潜伏的低隆起,其中双湖—雅曲段基底埋深5～7 km,雅曲—岗尼段基底埋深7～9 km;即中央隆起带基底自西向东"台阶状"降低,隆起的幅度和分布范围受到近南北向断裂控制.构造分层表明,与南羌塘地块相比,北羌塘地块的基底隆起幅度小、稳定性更好.南北羌塘基底地球物理属性的显著差异说明羌塘盆地并不存在统一的前寒武系变质基底,中央隆起带的形成应该与古特提斯洋关闭时形成的混杂岩带有关. 相似文献
2.
羌塘含油气盆地是我国境内最大的中新生代海相沉积盆地.羌塘地体内的中央隆起将盆地分为南北两个盆地.中央隆起带构造属性认识存在两种截然不同的分歧,一是伸展环境下形成,整个羌塘盆地有着同一的基底.而另一认识其是一古特提斯缝合带,其两侧盆地具有不同的演化机制.调查羌塘中央隆起的深部结构特征及其与南北两侧的盆地间的构造关系是认识羌塘盆地基底性质及其油气远景之关键科学问题.尽管羌塘地体在青藏高原形成演化过程中遭到了强烈改造,但在收集并分析已有地球物理资料基础上认为其深部结构仍有可能被完整保存.因此,利用密集宽频带流动台网观测,获取其深部结构,进而研究其与两侧盆地关系,是当前羌塘含油气盆地研究之重要突破口,同时该项研究符合我国当前国家油气资源战略评估政策. 相似文献
3.
大丰—包头剖面以"高密度观测点距与炮距"为特点,我们在1334 km测线上获得了21炮高信噪比的地震资料.在对Pg波震相特点分析基础上利用反演方法处理、构建了基底的精细结构图像,揭示了沿剖面不同构造地块基底结构的差异.苏北盆地基底埋深4.5~9.0 km、苏鲁隆起1.5~2.0 km,基底埋深与速度结构的强烈起伏变化可视其为华北与扬子板块碰撞、挤压构造环境下形成复杂的构造格局在地震学上的体现;鲁西隆起区基底埋深浅、速度高,结构稳定;华北盆地Pg波到时滞后、视速度低,基底埋深7.0~10.km,速度结构与基底面存在局部的起伏变化.诸多现象揭示出该区为新生代沉积巨厚、规模较大的基底坳陷区.同时在盆地内不同构造单元基底结构呈局部分块、凹陷与凸起并存的构造格局,显示出新生代沉积活动显著、变化强烈、结构不稳定的构造特点;太行山前断裂、聊兰断裂是具有显著地震学标志的断裂构造带,断裂两侧基底界面呈现出"断崖式塌陷"和速度结构的强烈横向非均匀性.综合研究认为,太行山前断裂是华北地区一条重要的构造带,它的复杂性不仅体现在两侧地形地貌、地层介质的截然不同,其基底埋深及速度结构、地壳及地幔岩石圈结构均存在显著的差异,其重要的标志是太行山以东不仅地壳厚度发生了相当规模的减薄,岩石圈的厚度也明显减薄,亦即形成了华北克拉.通破坏在东西部其基底一地壳一岩石圈的结构在空间上具有明显的差异性及强烈的横向非均匀性. 相似文献
4.
青藏高原内部除大规模的东西向走滑断裂以外,另一个显著的地质特征就是在藏南及高原腹地广泛发育东西向的伸展构造,形成走向近南北的断裂构造,如亚东一谷露裂谷带及双湖断裂.伸展构造已经成为青藏高原地质研究的一个焦点问题.在羌塘地块89°E附近存在明显的低重力、负磁、深度达300 km的低速异常及连通壳幔的高导异常,且地表伴生大规模的新生代火山岩,这些特殊的地质及地球物理场特征的发生位置与地表双湖断裂的位置基本对应.本文通过卫星重力数据的多尺度小波分析结果发现,双湖断裂之下,存在一明显由上地壳一直向下延伸至地幔深部的低重力异常,说明双湖断裂向下延伸深度大,且上下连通性好.结合已有的地质和地球物理资料,认为由于双湖断裂的存在,使得深部幔源岩浆沿断裂构造薄弱带上涌,从而导致羌塘地块之下壳幔温度的升高及大规模部分熔融的发生. 相似文献
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本文通过对羌塘盆地内49个临时宽频带地震观测台阵数据的接收函数分析,采用H-κ叠加和CCP 叠加成像两种方法,获得到了藏北羌塘中部莫霍面深度以及泊松比分布.作为羌塘盆地构造单元的南缘边界,班公湖-怒江缝合带下的Moho存在一个南深北浅、断距约10 km的台阶;把羌塘盆地分为两部分的羌塘中央隆起带下存在一个3 km的Moho台阶;北羌塘盆地下的Moho 平均深度约为60 km,而南羌塘约为63 km.羌塘高原下的近水平Moho结构可能是受到印度大陆北向俯冲作用下的青藏高原隆升过程中Moho再均衡所致或者与其构造演化有关.泊松比值具有明显的构造分区特征,如南羌塘下的泊松比平均为0.31,双湖缝合带下的泊松比接近正常值,为0.265,而北羌塘的泊松比平均为0.285. 相似文献
6.
《中国科学:地球科学》2015,(8)
从长1300余公里的盐城-包头深地震宽角反射/折射剖面21次爆破所得到的地震记录截面中,识别出6组清楚的壳内震相和1组岩石圈界面反射震相,采用射线追踪技术得到了华北克拉通东部、山西断陷带和银川-河套裂陷带岩石圈二维P波速度结构.研究结果表明,太行山东、西两侧岩石圈结构差异明显,太行山不仅是重力梯度带,也是一条岩石圈厚度的突变带和岩石成分分隔带.太行山以东的华北克拉通东部中新生代岩石圈结构遭受强烈改造和破坏,岩石圈厚度减薄至70~80 km;华北盆地有巨厚的新生代沉积盖层,结晶基底最深处约7.0 km,地壳厚度减薄至约31.0 km;鲁西隆起区结晶基底相对较浅,埋深1.0~2.0 km,地壳厚度33.0~35.0 km;苏北盆地有较厚的新生代沉积,结晶基底最大埋深5.0~6.0 km,地壳厚度31.0~32.0 km;郯庐断裂是一条岩石圈级别的深大断裂,其两侧速度结构差异明显,在华北克拉通东部的岩石圈破坏中起着重要作用.太行山以西地壳厚度明显增厚,山西断陷带下方地壳厚度约46 km,且其下方中地壳上部存在速度小于6.1 km s?1的低速结构.结合其他地球物理探测研究成果,环鄂尔多斯块体的陕西-山西断陷带和银川-河套裂陷带岩石圈遭受的破坏是不均匀的,其岩石圈厚度在大同-包头附近约为80~90 km,在定襄-神木附近为75~137 km,在安阳-宜川附近为80~120 km.造成岩石圈不均匀破坏的原因可能是环鄂尔多斯古老的构造带在长期的构造演化过程中,受多期构造事件影响而活化,被多次改造弱化,弱化的程度与鄂尔多斯块体的作用有关,在新生代印度板块与欧亚大陆的陆-陆碰撞和青藏高原块体北东向推挤的作用下,其岩石圈受到进一步改造减薄. 相似文献
7.
《中国科学:地球科学》2017,(2)
位于南北构造带北段的贺兰山和银川盆地是华北克拉通西部的一个板内构造变形带和活动构造带,有着复杂的形成和演化历史,对该区复杂的地质构造和现代地震活动有着重要的控制作用.2014年初,跨银川盆地和贺兰山完成的长度135km的深地震反射剖面揭示了该区的岩石圈层结构和断裂的深浅构造特征.研究结果表明,沿剖面莫霍面埋深自东向西逐渐加深,地壳厚度40~48km,且不同构造部位的地壳反射结构图像、速度分布、壳内界面形态和莫霍面起伏存在着明显差异.深地震反射剖面揭示,贺兰山两侧有着不同的断裂构造特征,在贺兰山东侧,黄河断裂、贺兰山东麓断裂以及银川盆地内的多条隐伏断裂均为第四纪以来仍在活动的正断层,控制了银川盆地的新生代沉积,在剖面上呈"负花状"构造展布;在贺兰山西侧,巴彦浩特断裂和贺兰山西麓断裂在剖面上表现为东倾的逆冲断层,使得贺兰山隆起区的中生代地层发生褶皱、冲断和结构变形;地壳深断裂位于银川盆地的西侧,该断裂倾角陡直,向下错断中-下地壳和莫霍面,向上可能与两组上地壳断裂相联系;这套不同时期形成的走滑、逆冲和正断并存的深浅断裂系统是该区盆山耦合、地壳结构变形和壳幔结构变化的构造条件.深地震反射剖面揭示的另外一个重要现象是,在贺兰山和银川盆地之下还存在有一组强能量的上地幔反射波组(UMR),其界面深度约为82~92km,暗示该区上地幔中存在有速度跃变层或速度间断面,反映了该区上地幔结构的纵向不均匀性.探测结果为进一步分析研究华北克拉通西部复杂的深部结构、不同地块的结构差异和深浅构造关系等提供了地震学证据. 相似文献
8.
本文综合利用广州海洋地质调查局历年来在中国南海西沙海域采集的重、磁、震资料,结合前人研究成果.采用了场源边缘识别、磁性体顶面埋深欧拉反演以及重、磁、震剖面联合反演等技术.针对西沙海槽盆地岩浆岩分布、重大断裂、深部构造等进行了综合研究.研究结果表明,盆地内岩浆岩主要形成于印支期和燕山期,大部分分布于盆地断阶带上;识剐出了NE向和EW向两组断裂.二者分别从北部和中部横贯盆地;盆地磁性基底埋深在6.0~12.6km之间。整体上呈"中部深、南北浅"的特征;西沙海槽盆地的莫霍面埋深在19~26 km之间,呈现出"南北深中部浅"的拉张裂谷特征.本文研究获取了西沙海槽盆地的基础地质构造特征.可深化盆地地质构造背景的认识,为该盆地下一步的油气工作提供基础研究资料. 相似文献
9.
黄骅坳陷盆地结构及构造单元展布受深断裂及盆地基底的控制与影响,利用重磁异常可以较大范围地揭示出控制盆地构造格局的深断裂及基底结构特征.本文综合考虑研究区盆地基底的宏观磁性差异以及存在的剩磁影响,采用对磁化方向依赖性小的磁异常模量数据,研究了黄骅盆地区域横向构造转换带的展布与磁性基底结构.识别出五条NW向与优势构造走向高角度相交的区域横向构造转换带和两条呈“T” 型展布的隐伏深断裂;研究区基底具有三分性结构特征,隐伏深断裂可能为三分基底的拼合线;基底结构差异及区域横向构造转换带共同控制了黄骅盆地“南北分区,东西分带”的宏观构造格局及沉积构造单元的展布. 相似文献
10.
藏北羌塘盆地查桑地区构造格局与演化 总被引：7，自引：0，他引：7
通过对近年新获得的各种地球物理和地质等资料的综合研究认为, 羌塘西部隆起查桑段不是一个简单的、长期隆升的古隆起, 而是总体由两三个东西向展布的大型南倾构造块体叠覆而成. 此结构和地球物理特征, 仅限于双湖-绒马之间, 不具区域意义. 其形成主要与该区东、西两侧中生代即发育近南北向转换断层、并与后期持续活动密切相关. 该段挤压、叠覆和隆升始于早白垩世羌塘盆地反转期, 与班公湖-丁青洋关闭相邻地块会聚直接有关; 始新世以来, 印度板块碰撞继续向北推挤, 该区的挤压、叠覆又得到进一步的发展和改造. 相似文献
11.
利用中国大陆东南缘四条北西向人工地震测深剖面的初至Pg波走时,使用有限差分层析成像方法反演剖面基底速度结构,并通过初始模型选取、射线数分布、走时拟合等手段分析结果的可靠度.研究结果表明,剖面表层速度比华北克拉通的地表速度高,闽东火山断拗带地表速度普遍高于西侧的闽西南坳陷带.相邻构造带的分界线两侧均有明显的速度横向变化,剖面东段的闽东火山断拗带内的东南沿海一带,速度变化较大,地层的褶皱变形要强于西段.基底埋深自西向东呈逐渐变浅的趋势,剖面东段的闽东火山断拗带基底起伏剧烈,基底深度与闽西南坳陷带相比较浅,与闽西北隆起带相比较深.西段的闽西北隆起带基底变化较为平缓,基底深度相对较浅;闽西南坳陷带基底深度明显加深,在龙岩新泉盆地内最深接近4 km.基底形态的起伏变化揭示出东南缘基底是坳陷与隆起并存的构造特征,与研究区近代的地质构造特征相吻合.邵武—河源、政和—大埔和长乐—诏安断裂带都切割基底,其中,政和—大埔断裂4 km深度下方有比较明显的低速异常带,结合本文以及现有的研究结果,进一步确认政和—大埔断裂是不同断块构造单元的分界. 相似文献
12.
羌塘盆地是我国最大的海相盆地.本文根据在羌塘盆地内布设的27个宽频带地震观测台站记录的远震波形数据,利用非线性复谱比反演算法得到各台站下方100 km深度范围内S波速度结构.结果表明.羌塘地区Moho深度较为平缓,平均深度为61 km;北羌塘地壳内低速层广泛分布;北羌塘具有两个较大的沉积盆地,龙尾错和白滩湖坳陷,沉积厚度分别有10 km和15 km.尽管北羌塘下地壳受到强烈的新生代火山岩作用改造,但是这种深部岩浆热作用会加速烃源岩中有机质的热演化历程.北羌塘两个盆地具有很好的油气前景.与北羌塘低速层分布相比,南羌塘下低速层更深,可能与班公怒江洋于中生代的俯冲消减及拉萨地体北向俯冲有关. 相似文献
13.
ShuaiJun Wang FuYun Wang JianShi Zhang ShiXu Jia ChengKe Zhang JinRen Zhao BaoFeng Liu 《中国科学:地球科学(英文版)》2014,57(9):2053-2063
For the first time on the Chinese mainland, long-range wide-angle seismic reflection/refraction profiling technology has been applied to seismic wave phases from different depths and with different attributes within the various blocks of the North China Craton to characterize the structure of the crust and upper mantle lithosphere. By comparative analysis of the seismic wave phase characteristics in each block across a 1500-km-long east-west profile, we have identified conventional Pg, Pci, PmP and Pn phases in the crust, made a clear contrast between PL1 and PL2 waves belonging to two groups of lithospheric-scale phases, and produced a model of crust-mantle velocity structures and tectonic characteristics after one- and two-dimensional calculations and processing. The results show that the thickness of the crust and lithosphere gradually deepens from east to west along the profile. However, at the reflection/refraction interface, seismic waves in each group show obvious localized changes in each block. Also, the depth to the crystalline basement changes greatly, from as much as 7.8 km in the North China fault basin to only about 2 km beneath the Jiaodong Peninsula and Taihang-Lüliang area. The Moho morphology as a whole ranges from shallow in the east to deep in the west, with the deepest point in the Ordos Block at 47 km; in contrast, the North China Plain Block is uplifting. The L1 interface of the lithosphere is observed only to the west of Taihang Mountains, at a relatively slowly changing depth of about 80 km. The L2 interface varies from 75 to 160 km and shows a sharp deepening to the west of Taihang Mountains, forming a mutation belt. 相似文献
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JOINT INVERSION OF AMBIENT NOISE AND SURFACE WAVE FOR S-WAVE VELOCITY OF THE CRUST AND UPPERMOST MANTLE BENEATH WEIHE BASIN AND ITS ADJACENT AREA 
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下载免费PDF全文 The Weihe Basin is the main component of the extrusion and escape shear zone between the ancient North China craton block in Ordos and the ancient Yangtze platform in Sichuan Basin, and carries the dynamic transmission from the main power source of the Qinghai-Tibet Block in the west to the North China and South China regions in the east. The basin itself plays multi roles in the east-west and north-south tectonic movement, and is an excellent site for studying the structural interlacing, dynamic transformation and transmission. At the same time, Weihe Basin is also a famous strong earthquake zone in China. Historically, there was a strong earthquake of magnitude 8 1/4 occurring in Huaxian County in 1556, causing huge casualties and property losses. In view of the special geological structures and the characteristics of modern seismicity activities in the Weihe fault-depression zone, it is necessary to carry out fine three-dimensional velocity structure detection in the deep part of Weihe Basin and its adjacent areas, so as to study the relationship between velocity structure and geological structural units and their evolution process, as well as the deep medium environment where earth￣quakes develop and occur.
We investigate the S-wave velocity structure beneath Weihe Basin and its adjacent regions based on continuous background noise data and teleseismic data recorded by 257 broadband stations in Shaanxi Province and its adjacent regions and China Seismological Science Array Exploration Project, and by adopting seismic surface wave inter-station method and background noise cross-correlation method, a total of 10 049 fundamental-mode Rayleigh surface wave phase velocity dispersion curves in the periods of 5~70s are obtained. Firstly, using the average dispersion curve in this study area, we obtain the one-dimensional average S-wave velocity structure model of the study area, and then we apply the ray-tracing surface-wave-dispersion direct inversion method to obtain the S-wave velocity structure of the crust and uppermost mantle (3~80km) beneath Weihe Basin and its adjacent regions. The test results of a 1°×1° grid checker board show that the recovery is good, except for the areas east of 111° and south of 32° of the study area, where there is almost no resolution. The imaging results show that the velocity structure beneath each tectonic unit in the study area has a certain distribution rule, and there is a good correlation between surface geological structure and deep velocity structure.
Based on the analysis of velocity slices at different depths and S-wave velocity structures of three profiles, and combined with existing geological structures, geophysics and other deep exploration research results, we obtain the following knowledge and conclusions:1)The thick sedimentary layer covering the top of Weihe Basin is the cause of low velocity anomaly in its shallow crust, the middle and upper crust of the basin are of low velocity structure, and the low-velocity zone extends about 25km, the Moho interface uplifts abruptly relative to both the Ordos Block and the Qinling orogenic belt on opposite sides, and high-speed materials from the upper mantle intrude into the lower crust, which may be related to the underplating of mafic-ultramafic materials from the upper mantle in Mesozoic-Cenozoic period; 2)The south Ordos Block is not a homogeneous whole, the low-velocity structure of the shallow crust in southern Ordos Block is thin in east and thick in west, which may be related to the overall tilting of the Ordos Basin since the Phanerozoic, as well as the differential uplift and strong and uneven denudation of the Ordos Block since the Late Cretaceous. The crustal structure of the south Ordos Block is relatively simple and homogeneous. There is no significant low-velocity structure in the curst of the block, which shows that the low-velocity structure in the crust does not penetrate the whole Ordos block. We speculate that the southern Ordos Block still maintains the stable craton property, and has not been reformed significantly so far; 3)The variation characteristics of deep structure of the Qinling orogenic belt reflect the deep crustal structure and tectonic deformation characteristics of the orogenic belt which are strongly reformed by land-land collision and suture between North China plate and Yangtze plate, intracontinental orogeny, uplift of Qinghai-Tibet Plateau and its northeastern expansion since the Late Hercynian-Indosinian period. The deep structure beneath the eastern and western Qinling orogenic belt is different and has the characteristics of segmentation. The low-velocity anomaly at the bottom of the lower crust of the orogenic belt may be affected by tectonic activities such as uplift and outward extension of the NE Tibetan plateau, and the analysis considers that there is little possibility of the existence of lower crustal circulation channel for the eastward flowing of Tibetan plateau materials in the Qinling orogenic belt. However, since the maximum depth from the inversion of this paper is 80km, which is located at the top of the upper mantle, our results cannot prove that there exists a mantle flow channel for the eastward flow of Tibetan plateau material beneath the Qinling orogenic belt. 相似文献
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Deep crustal structures of eastern China and adjacent seas revealed by magnetic data 总被引：5，自引：0，他引：5
Through reduction to the North Pole and upward continuation of the total field magnetic anomalies, we analyze magnetic patterns
and spatial distributions of different tectonic blocks and crustal faults in eastern China and adjacent seas. Depths to the
Curie isotherms are further estimated from radially averaged amplitude spectra of magnetic data reduced to the pole. Data
reductions effectively enhance boundaries of regional tectonic belts, such as the Dabie ultra-high metamorphic belt, the Tanlu
Fault, and the Diaoyudao Uplift. Curie depths are estimated at between 19.6 and 48.9 km, with a mean of 31.7 km. The Subei
Basin and the south Yellow Sea Basin in the lower Yangtze block show relatively deep Curie isotherms, up to about 35 km in
depth, whereas in the surrounding areas Curie depths are averaged at about 25 km. This implies that the lower Yangtze Block
has experienced a unique tectonic evolution and/or has unique basement lithology and structures. From a regional perspective,
sedimentary basins, such as the Subei Basin, the south Yellow Sea Basin, and the East China Sea Basin, normally show deeper
Curie isotherms than surrounding uplifts such as the Diaoyudao Uplift and the Zhemin Uplifts. Curie isotherms also upwell
significantly in volcanically active areas such as the Ryukyu Arc and the Cheju Island, confirming strong magmatic and geothermal
activities at depth.
Supported by National Natural Science Foundation of China (Grant Nos. 40776026 and 40876022) and National Basic Research Program
of China (Grant No. 2007CB411702) 相似文献
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四川西部的理塘—巴塘地区以近SN向的断裂构造为主,并发育 1组NNE和NW向的共轭剪切破裂带。文中在详细的TM卫片和航空照片判译的基础上,以活动构造地貌学为主线,重点解析了该地区断裂构造晚更新世—全新世以来活动的表现形式,确定近SN向的金沙江断裂带晚第四纪以来的近EW向的缩短速率为 2~3mm/a,NNE向巴塘断裂的右旋水平滑动平均速率为1. 3~2. 7mm/a,NW向理塘断裂的左旋水平滑动平均速率为 2 .6~4. 4mm/a。结合地球物理场、震源机制解、GPS测量等资料,分析了该地区现今地壳运动的总体态势及其所导致的块体运移规律,指出 1989年巴塘 6 .7级震群的成因,是由于NNE向巴塘断裂和NW向理塘断裂共轭剪切所派生的近EW向正断层的张性破裂所致,揭示了一个挤压构造环境内正断层发震的典型震例 相似文献