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文章系统梳理了青藏高原东部地区晚新生代重大构造事件的沉积记录、岩浆记录和构造变形响应,重新厘定了青藏运动或横断事件的起始时限,建立了青藏高原东部晚新生代构造演化序列与挤出造山构造体系。研究认为,发生在上新世之前的青藏运动是青藏高原东部最重要的构造作用阶段,起始于距今12~8 Ma,并持续到上新世早期,持续时间达6~8 Ma。在这个构造运动阶段,青藏高原东部地块(川滇地块、川青地块、西秦岭构造带和陇中地块等)有序地向东挤出,受到鲜水河、东昆仑、海原等WNW-ESE向大型断裂左旋走滑运动调节,构造挤出同时伴随地块内部逆冲褶皱变形,导致地壳增厚和高原东缘山脉快速崛起;构造挤出也超越了现今东缘地貌边界,向东扩展导致扬子地块盖层滑脱褶皱,形成龙泉山、大凉山等褶皱构造带。上新世出现的砾石层(东缘前陆地带的大邑砾石层、临夏盆地的积石砾石层、兰州盆地的五泉砾石层等)标志了青藏高原东部差异性构造地貌的形成。上新世晚期至早更新世时期(3.6~1.0 Ma)对应一个构造松弛阶段,青藏高原东部整体进入冰冻时期,沿其东缘发育一系列受正断层控制的南北向伸展断陷盆地,如安宁河谷地、元谋盆地、盐源盆地、滇西北盆地群等,其中加积了以昔格达组为代表的稳定河湖相沉积。发生在早、中更新世之交(距今1.0~0.6 Ma)的昆—黄运动或元谋事件使青藏高原东部地块进一步向东挤出、东缘地壳逆冲增厚和年轻山系加速隆升。晚更新世以来的构造运动称为共和运动或最新构造变动阶段,起始于距今约120 ka,青藏高原东缘构造变形系统出现重大分化,南段川滇菱形地块发生绕喜玛拉雅东构造结的顺时针旋转运动,形成川滇双弧形旋扭构造体系;而中段川青地块的挤出伴随东缘龙门山断裂带的右旋走滑运动和秦岭山系的向东挤出。在这个最新构造变动阶段,青藏高原东部下地壳通道流可能是重要的深部构造驱动因素。 相似文献
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2008年5月12日在青藏高原东缘龙门山断裂带中段发生汶川8.0级特大地震。大震发生时释放应力并对震源区及外围构造应力场产生影响,受汶川地震断层破裂方式和强度空间差异性的影响,震后龙门山断裂带地壳应力场也应表现差异特征,至今鲜有针对该科学问题深入的分析和讨论。经过系统收集、梳理汶川地震后沿龙门山断裂带水压致裂地应力测量数据与2008年汶川地震中强余震序列震源机制解资料,对汶川地震后龙门山断裂带中上地壳构造应力场进行厘定,通过与震前构造应力场对比,深入探讨了汶川8.0级地震对龙门山断裂带地壳应力场的影响,进而对汶川震后应力调整过程及青藏高原东缘龙门山地区深部构造变形模式进行研究,研究结果表明:受汶川8.0级地震的影响,震后龙门山断裂带地壳构造应力场空间分布具有差异性,近地表至上地壳15 km深度范围,映秀—青川段最大主应力方向为北西西向、地应力状态为逆走滑型,青川东北部最大主应力方向偏转至北东东向、应力状态转变为走滑型;15~25km深度范围,龙门山断裂带最大主应力方向仍为北西—北西西向、应力状态以逆冲型为主。汶川8.0级地震后,龙门山断裂带中地壳北西西向逆冲挤压的构造应力特征进一步支持了青藏高原东缘龙门山地区东西两侧刚性块体碰撞挤压、逆冲推覆的动力学模式。 相似文献
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汶川8级大地震同震破裂的特殊性及构造意义——多条平行断裂同时活动的反序型逆冲地震事件 总被引：33，自引：2，他引：31
汶川地震是有仪器记录以来发生的世界上最大的板内逆冲型地震之一。野外调查表明,沿北东走向的龙门山断裂带上,至少有两条逆冲断裂同时参与汶川地震的同震破裂过程,即北川断裂和安县灌县断裂（彭灌断裂）。倾向北西的高角度北川逆冲断裂上的地表破裂长度大于200 km,可能达225 km。运动方式在南部表现为以北西盘抬升的逆冲为主,往北东转为逆冲右旋走滑,走滑分量与垂向陡坎高度相当,陡坎高度最大值约为11 m。在彭灌断裂上,地表破裂表现为北西盘抬升的近纯逆冲性质的破裂,破裂长度达70 km,陡坎最高达3~3.5 m。汶川地震是世界上第一次明确记录到多条平行断裂参与同震破裂的逆冲型地震,而且因发震断层是龙门山断裂带内部的高角度逆冲断裂,而非断裂带前锋的低角度逆冲断裂,所以汶川地震属于反序型逆冲断裂活动。这与1999年我国台湾7.5级集集地震和2005年克什米尔7.6级地震类似,说明反序型逆冲地震具有普遍性。汶川地震这一震级大、破裂长的逆冲地震事件是对目前流行的青藏高原下地壳流动的变形假说提出的严峻挑战,同时也表明加强青藏高原东缘南北地震带上其他滑动速率较低但同样具有发生大地震可能性的活动断裂的滑动速率和古地震定量研究的紧迫性,因为这一地区人口密度与东部相当,但发生强震的频率更高。 相似文献
4.
龙门山地震带的地质背景与汶川地震的地表破裂 总被引：17，自引：0，他引：17
李勇 黄润秋 周荣军 Alexander L. DENSMORE Michael A. ELLIS 闫亮 董顺利 Nicholas RICHARDSON 张毅 何玉林 陈浩 乔宝成 马博琳 《工程地质学报》2009,17(1):3-18
龙门山位于青藏高原与扬子地台之间, 系由一系列大致平行的叠瓦状冲断带构成, 自西向东发育汶川茂汶断裂、映秀北川断裂和彭县灌县断裂，并将龙门山划分为3个构造地层带，分别为变形变质构造地层带（主要由志留系泥盆系浅变质岩和前寒武系杂岩构成）、变形变位构造地层带（主要由上古生界三叠系沉积岩构成）、变形构造地层带（主要由侏罗系至第三系红层和第四纪松散堆积构成）。
龙门山断裂带属地震危险区，3条主干断裂皆具备发生7级左右地震的能力，其中映秀北川断裂是引发地震的最主要断层，据对彭县灌县断裂青石坪探槽场地的研究结果表明，在该断裂带上最晚的一次强震发生在93040a.B.P.左右，据此，可以初步判定，这3条主干断裂的单条断裂上的强震复发间隔至少应在1000a左右，表明龙门山构造带及其内部断裂属于地震活动频度低但具有发生超强地震的潜在危险的特殊断裂，以逆冲-右行走滑为其主要运动方式。
汶川地震属于逆冲走滑型的地震，地表破裂分布于映秀北川断裂带和彭县灌县断裂带上。根据近南北向的断裂（小鱼洞断层、擂鼓断层和邓家坝断层）和地表断距可将映秀北川断层的地表破裂带划分为两个高值区和两个低值区，两个高值区分别位于南段的映秀-虹口一带和位于中北段的擂鼓北川县城邓家坝一带；两个低值区分别位于中南段的白水河茶坪一带和北段的北川黄家坝至平武石坎子一带，两个高值区分别与小鱼洞断层和擂鼓断层相关。根据保存于破裂面上的擦痕，可将该地震破裂过程划分为两个阶段，早期为逆冲作用，晚期为斜向走滑作用，其与地壳增厚构造模式和侧向挤出摸式在青藏高原东缘的推论具有不吻合性。鉴于龙门山的表层运动速率与深部构造运动速率具有不一致性，初步探讨了龙门山地区的地表过程与下地壳流之间的地质动力模型，认为下地壳物质在龙门山近垂向挤出和垂向运动，从而造成导致龙门山向东的逆冲运动、龙门山构造带抬升和汶川特大地震。在此基础上，根据汶川地震所引发的地质灾害，对地震灾后重建提出了的几点建议。 相似文献
5.
青藏高原东北缘海原断裂带新生代构造演化 总被引：4，自引：0，他引：4
海原断裂带作为青藏高原东北缘构造变形最显著断裂带之一,记录了青藏高原向北东扩展的构造信息。在详细的构造测量基础上,初步提出海原断裂带新生代以来的古构造应力场序列,反演了其新生代构造演化历史。详细构造解析表明,海原断裂带新生代以来主要经历了5个构造演化历史阶段,即始新世-中新世NWSE向构造伸展与沉积盆地发育、中新世晚期-上新世NNESSW向构造挤压与海原断裂带右行走滑活动、上新世末-早更新世NESW向构造挤压与强烈褶皱逆冲活动、晚更新世晚期以来ENEWSW向构造伸展与断陷盆地发育、全新世以来NESW向构造挤压作用与断裂带强烈左行走滑活动。变形分析表明海原断裂带现今地貌格局主要缘于上新世末-早更新世NESW向强烈逆冲活动,后期ENEWSW向构造挤压作用导致断裂走滑活动,并改造了局部地貌,主要表现为沿断裂带发育一系列第四纪小型拉分盆地。该带新生代构造演化研究,为探讨青藏高原东北缘新构造演化提供了具体构造证据。 相似文献
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青藏高原向东挤出的变形响应及南北地震带构造组成 总被引：12，自引：1，他引：12
受青藏高原物质在南北挤压下向东逸出的影响 ,四川地块、鄂尔多斯地块、川滇地块和滇西地块均发生了不同性质的变形响应。根据航磁异常揭示的四川、鄂尔多斯盆地基底构造样式和滇西地区的地质构造研究结果 ,在主要由变质褶皱基底组成的四川地块发生平行龙门山断层的逆冲推覆 ,基底岩石发生递进褶皱缩短的同时 ,由华北变质结晶基底组成的鄂尔多斯地块在前期逆冲推覆构造的基础上 ,结晶基底沿一系列近东西向左行走滑断层向东错移。滇西和川滇地块则分别沿金沙江—红河断裂 (2 0Ma前后 )和鲜水河—小江断裂 (5Ma前后 )发生了大规模的左行位移。发生在滇西、川滇、四川和鄂尔多斯地块上的最新构造变动叠加或改造了先存构造 ,并且表现为从南向北、由盖层向基底发展的趋势 ,变形程度自西向东减弱 ,反映了青藏高原持续同构造伸展作用的边缘和远程效应。青藏高原东缘多层次、多阶段的现今构造变动引发的地震活动组成了宏观的南北地震带。 相似文献
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龙门山断裂活动和川西高原隆升历史的裂变径迹测年 总被引：2，自引：0，他引：2
通过12个构造岩、变质砂岩和花岗岩样品的磷灰石裂变径迹测年年龄分析,结合前人研究成果,初步确定了青藏高原东缘龙门山地区晚新生代主要断裂活动时期和区域隆升历史。结果表明,龙门山逆冲推覆构造带2条主断裂:汶川—茂县断裂和映秀—北川断裂,最晚一次强烈活动发生在早更新世(FT年龄为1.2～1.3 Ma),高原内部北西向米亚罗断裂在中更新世(约0.5 Ma)发生过强烈活动;后龙门山逆冲推覆构造带在中新世晚期开始快速隆升,而高原内部强烈隆升发生在上新世末至中更新世。高原隆升导致深切河谷地貌的形成和发育。 相似文献
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大陆构造变形与地震活动——以青藏高原为例 总被引：5，自引：0，他引：5
大陆内部构造变形和地震活动往往突显出复杂的、区域性的特征,很难用板块构造理论来解释。青藏高原是大陆构造变形的典型实例,具有不同构造变形的分区特征,不仅表现在物质组成、地形地貌和断裂组合等方面的不同,而且还表现出不同的地震活动特征。东昆仑断裂带以北的青藏高原北部地块,主要发育一系列挤压环境下的盆岭构造,表现为以连续变形为特征的上地壳挤压缩短变形;高原中北部巴颜喀拉地块,具有整体向东运动的特点,变形主要集中在其边缘,表现为刚性块体运动特征。在东部,由于稳定的四川盆地(扬子地块)的阻挡,位于龙日坝和龙门山断裂带之间相对坚硬的龙门山地区受到东西向强烈挤压,西部边界为伸展变形;在高原中央腹地羌塘地块西部,由于上地壳物质在向东挤出的驱动下不断变形,沿一系列小型正断层和走滑断层以伸展变形为主,表现为弥散型变形特征。相比之下,羌塘地块的东部向东-南东方向挤出,在大型走滑断层之间形成一个刚性块体;高原南部地块以东西向伸展的南北向裂谷系为主要变形特征,高原南缘以南北向挤压的大型逆冲断裂系为特征。历史地震和仪器记录的大地震(M≥8)只发生在高原东北和东南部的大型走滑带,以及东部和南部边缘的大型逆冲断裂上,沿后者更为频发。到目前为止,高原其他地区只发生了8级以下地震。青藏高原这种分区域的地壳变形形式和地震活动分布是大陆构造变形的重要特征。 相似文献
9.
2008年5月12日14时28分,青藏高原东缘龙门山地区（四川汶川）发生了Ms8.0级地震。震后野外考察表明,5.12汶川地震发生在NE走向的龙门山断裂带上,该断裂带晚新生代以来的逆冲速率小于1mm/a,GPS观察结果表明其缩短速率小于3mm/a。这次5.12汶川地震造成了多条同震逆冲地表破裂带,总体长约275km,宽约15km,发震断裂机制主要为逆冲作用（由NW向SE逆冲）伴随右旋走滑。地表主破裂带沿龙门山断裂带的映秀—北川断裂发育,长约275km,笔者称为映秀—北川破裂带,破裂带具有逆冲兼右旋走滑性质。地表次级破裂带沿龙门山断裂带的前缘断裂安县—灌县断裂南段发育,长80km,笔者称为汉旺破裂带,破裂带基本为纯逆冲性质。在这两条破裂带之间发育两条更次一级的同震地表破裂带：一条长约20km呈NE走向的地表破裂带,笔者称为深溪沟破裂带,由于这条破裂带靠近主破裂带南段,并且与主破裂带变形特征一致,因此,笔者将深溪沟破裂带划归映秀—北川破裂带;另一条长约6km呈NW走向、由SW向NE逆冲并兼有左旋滑动的地表破裂带,笔者称为小鱼洞破裂带,它连接映秀—北川破裂带和汉旺破裂带,成为侧向断坡。另外,在灌县—安县断裂东侧的四川盆地内,由都江堰的聚源到江油发育一条NE向的沙土液化带,它可能是四川盆地西部深部盲断裂活动的结果。同震地表破裂带的分布特征表明,龙门山断裂带活动断裂具有强烈的逆冲作用并伴随较大的右旋走滑,断裂向四川盆地扩展。在龙门山断裂带上类似2008年5月12日Ms8.0汶川大地震的强震复发周期为3000～6000a。 相似文献
10.
岷江断裂带晚新生代逆冲推覆构造：来自钻孔的证据 总被引：6，自引：0，他引：6
岷江断裂带由2个不同性质的断裂组成:早期岷江逆冲断裂和晚期岷江正断裂。野外地质调查和钻孔资料发现在岷江西侧山麓之下存在一套厚度大于110m的早更新世灰黑色湖相地层,三叠系灰岩逆掩在这套湖相地层之上。由此确定岷江断裂是一条西倾的逆冲断层,逆冲作用发生在中更新世之前。在中更新世时期,岷江逆冲断裂发生构造负反转,在其前缘形成一条东倾的正断层,它控制了岷江上游漳腊盆地的发育。本文认为,岷山地区现今地震活动并非受控于岷江断裂带,而可能受到虎牙断裂及岷山隆起深部滑脱构造的控制,岷江断裂带位于该深部滑脱构造的上部。进而认为逆冲—推覆构造样式可能是青藏高原东缘晚新生代造山和快速隆升的主要变形机制。 相似文献
11.
Zhong-hai Wu Pei-sheng Ye Patrick J. Barosh Zhen-han Wu 《Journal of Asian Earth Sciences》2011,40(4):943-957
A Mw 6.3 magnitude earthquake occurred on October 6, 2008 in southern Damxung County within the N–S trending Yangyi graben, which forms the northern section of the Yadong-Gulu rift of south-central Tibet. The earthquake had a maximum intensity of IX at the village of Yangyi (also Yangying) (29°43.3′N; 90°23.6′E) and resulted in 10 deaths and 60 injured in this sparsely populated region. Field observations and focal mechanism solutions show normal fault movement occurred along the NNE-trending western boundary fault of the Yangyi graben, in agreement with the felt epicenter, pattern of the isoseismal contours, and distribution of aftershocks. The earthquake and its tectonic relations were studied in detail to provide data on the seismic hazard to the nearby city of Lhasa.The Damxung earthquake is one of the prominent events along normal and strike-slip faults that occurred widely about Tibet before and after the 2008 Mw 7.9 magnitude Wenchuan earthquake. Analysis of these recent M ? 5.0 earthquake sequences demonstrate a kinematic relation between the normal, strike-slip, and reverse causative fault movements across the region. These earthquakes are found to be linked and the result of eastward extrusion of two large structural blocks of central Tibet. The reverse and oblique-slip surface faulting along the Longmenshan thrust belt at the eastern margin of the Tibetan Plateau causing the Wenchuan earthquake, was the result of eastward directed compression and crustal shortening due to the extrusion. Prior to it, east–west extensional deformation indicated by normal and strike-slip faulting events across central Tibet, had led to a build up of the compression to the east. The subsequent renewal of extensional deformational events in central Tibet appears related to some drag effect due to the crustal shortening of the Wenchuan event. Unraveling the kinematical relation between these earthquake swarms is a very helpful approach for understanding the migration of strong earthquakes across Tibet. 相似文献
12.
Active Faulting Pattern,Present-day Tectonic Stress Field and Block Kinematics in the East Tibetan Plateau 总被引：1，自引：0，他引：1
ZHANG Yueqiao DONG Shuwen YANG Nong Key Laboratory of Neotectonic Movement Geohazard Ministry of L Resources Beijing China Institute of Geomechanics Chinese Academy of Geological Sciences China Chinese Academy of Geological Sciences Beijing China 《《地质学报》英文版》2009,83(4)
This paper examines major active faults and the present-day tectonic stress field in the East Tibetan Plateau by integrating available data from published literature and proposes a block kinematics model of the region.It shows that the East Tibetan Plateau is dominated by strike-slip and reverse faulting stress regimes and that the maximum horizontal stress is roughly consistent with the contemporary velocity field,except for the west Qinling range where it parallels the striking of the major strike-slip... 相似文献
13.
关于汶川地震发震机制 总被引：10，自引：0，他引：10
2008年5月12日汶川8级地震的发震断层是四川龙门山逆冲带的前锋灌县—安县断层,或此断层附近新产生相同产状的断层。发震断层走向NE倾向NW,逆冲兼右行平移。汶川地震的发震机制是印藏陆-陆碰撞后,印度次大陆活塞状嵌入欧亚板块造成青藏高原东部向SEE方向近水平挤压,在龙门山冲断带前锋向东南逆冲到四川盆地,构造应力积累和释放的结果。汶川地震演示了一个青藏高原东缘龙门山隆起的构造模型,即其经由龙门山冲断带的地壳冲断作用和缩短作用而隆升。这与Burchfiel的模型不同,该模型认为龙门山上升是由于韧性下地壳流受到四川盆地高强度地壳阻挡而上涌所致。这两种模型可能各有其适用时间阶段,然而本文的模型是不可或缺的,因汶川地震已显示了它的真实性。 相似文献
14.
Decomposition and Evolution of Intracontinental Strike-Slip Faults in Eastern Tibetan Plateau 总被引：2，自引：0，他引：2
Little attention had been paid to the intracontinental strike-slip faults of the Tibetan Plateau. Since the discovery of the Longriba fault using re-measured GPS data in 2003, an increasing amount of attention has been paid to this neglected fault. The local relief and transverse swath profile show that the Longriba fault is the boundary line that separates the high and flat tomography of the Tibet plateau from the high and precipitous tomography of Orogen. In addition, GPS data shows that the Longriba fault is the boundary line where the migratory direction of the Bayan Har block changed from eastward to southeastward. The GPS data shows that the Longriba fault is the boundary fault of the sub-blocks of the eastern Bayan Har block. We built three-dimensional models containing the Longriba fault and the middle segment of the Longmenshan fault, across the Bayan Har block and the Sichuan Basin. A nonlinear finite element method was used to simulate the fault behavior and the block deformation of the Eastern Tibetan Plateau. The results show that the low resistivity and low velocity layer acts as a detachment layer, which causes the overlying blocks to move southeastward. The detachment layer also controls the vertical and horizontal deformation of the rigid Bayan Har block and leads to accumulation strain on the edge of the layer where the Longmenshan thrust is located. After a sufficient amount of strain has been accumulated on the Longmenshan fault, a large earthquake occurs, such as the 2008 Wenchuan earthquake. The strike slip activity of the Longriba fault, which is above the low resistivity and low velocity layer, partitions the lateral displacements of the Bayan Har block and adjusts the direction of motion of the Bayan Har block, from the eastward moving Ahba sub-block in the west to southeastward moving Longmenshan sub-block in the east. 相似文献
15.
汶川地震断裂带科学钻探1号井(WFSD-1)非弹性应变恢复法(ASR法)三维地应力测试与"5.12"汶川地震的形成机制 总被引：1，自引：0，他引：1
汶川地震断裂带科学钻探1号井(WFSD-1)的ASR三维地应力测试结果表明,龙门山前陆逆冲带与其下伏的龙门山前陆盆地和上覆的松潘-甘孜地块的构造及地应力状态存在有重大差异。从整体上看,在汶川地震中,龙门山前陆逆冲带表现为在强烈的区域性挤压背景下,深部物质沿壳内拆离层自SW向NE方向的"层状"流动,在地壳上部转化为沿映秀-北川断裂(YBF)的快速垂向挤出,而其西侧的松潘-甘孜地块作自SE往NW方向的重力滑覆,东侧的龙门山前陆盆地则表现为自NE往SW方向的走滑或右行旋转。晚新生代以来,扬子地块相对于青藏高原东缘的龙门山造山带并无明显的或大尺度的陆内俯冲作用发生。龙门山前陆逆冲带深部高温低粘度物质垂直向上的、快速的流动和挤出,直接导致了"5.12"汶川地震的发生,而松潘-甘孜地块E向扩展导致龙门山前陆带的强烈挤压和陆壳增厚及深部应力和地震能量的积聚则是诱导深部位移场发生突变和物质快速垂向挤出的主因,E向扩展是深部地震能量积聚和快速垂向挤出作用的必要条件,而非地震发生的直接原因。ASR地应力测试得出的主压应力方向完全平行于GPS同震速度场的位移方向,似乎表明ASR测试获得的原地应力场或许真实地反映了或最接近于地震过程中的构造应力状态。 相似文献
16.
Active Faulting Pattern, Present-day Tectonic Stress Field and Block Kinematics in the East Tibetan Plateau 总被引：9，自引：1，他引：8
Abstract: This paper examines major active faults and the present-day tectonic stress field in the East Tibetan Plateau by integrating available data from published literature and proposes a block kinematics model of the region. It shows that the East Tibetan Plateau is dominated by strike-slip and reverse faulting stress regimes and that the maximum horizontal stress is roughly consistent with the contemporary velocity field, except for the west Qinling range where it parallels the striking of the major strike-slip faults. Active tectonics in the East Tibetan Plateau is characterized by three faulting systems. The left-slip Kunlun-Qinling faulting system combines the east Kunlun fault zone, sinistral oblique reverse faults along the Minshan range and two major NEE-striking faults cutting the west Qinling range, which accommodates eastward motion, at 10–14 mm/a, of the Chuan-Qing block. The left-slip Xianshuihe faulting system accommodated clockwise rotation of the Chuan-Dian block. The Longmenshan thrust faulting system forms the eastern margin of the East Tibetan Plateau and has been propagated to the SW of the Sichuan basin. Crustal shortening across the Longmenshan range seems low (2–4 mm/a) and absorbed only a small part of the eastward motion of the Chuan-Qing block. Most of this eastward motion has been transmitted to South China, which is moving SEE-ward at 7–9 mm/a. It is suggested from geophysical data interpretation that the crust and lithosphere of the East Tibetan Plateau is considerably thickened and rheologically layered. The upper crust seems to be decoupled from the lower crust through a décollement zone at a depth of 15–20 km, which involved the Longmenshan fault belt and propagated eastward to the SW of the Sichuan basin. The Wenchuan earthquake was just formed at the bifurcated point of this décollement system. A rheological boundary should exist beneath the Longmenshan fault belt where the lower crust of the East Tibetan Plateau and the lithospheric mantle of the Yangze block are juxtaposed. 相似文献
17.
The Deep Geophysical Structure of the Middle Section of the Longmen Mountains Tectonic Belt and its Relation to the Wenchuan Earthquake 总被引：1，自引：0，他引：1
Investigation of the deep geophysical structure of the Longmen Mountains tectonic belt and its relation to the Wenchuan Earthquake is important for the study of earthquakes. By using magnetotelluric sounding profiles of the Luqu–Zhongjiang and Anxian–Suining; seismic sounding profiles of the Sichuan Maowen–Chongqing Gongtan, the Qinghai Huashi Gorge–Sichuan Jianyang, and the Batang–Zizhong; and magnetogravimetric data of the Longmen Mountains region, the deep geophysical structure of the Songpan–Ganzi block, the western Sichuan foreland basin, and the Longmen Mountains tectonic belt and their relation was discussed. The eastward extrusion of the Qinghai–Tibet Plateau thrusts the Songpan–Ganzi block upon the Yangtze block, which obstructs the eastward movement of the Qinghai–Tibet Plateau. The Maoxian–Wenchuan, Beichuan–Yingxiu, and Anxian–Guanxian faults of the Longmen Mountains fault belt dip to northwest with different dip angles and gradually converge in the deeper parts. Geophysical structure suggests that an intracrustal low-velocity, low-resistivity, and high-conductivity layer is common between the middle and upper crust west of the Longmen Mountains tectonic belt but not in the upper Yangtze block. The Sichuan Basin has a thick low-resistance sedimentary layer on a stable high-resistance basement; moreover, there are secondary paleohighs and depression structures at the lower part of the western Sichuan foreland basin with characteristic of high magnetic anomalies, whereas the Songpan–Ganzi block has a high resisitivity cover of upper crust and continues to a low-resistance layer. Considering the Longmen Mountains tectonic belt as the boundary, there are Bouguer gravity anomalies of "one belt between two zones." Thus, we infer that there is a corresponding relation between the inferred crystalline basement of the Songpan block and the underlying basin basement of the Longmen Mountains fault belt. Furthermore, there may be an extensive ancient Yangtze block, which is west of the Ruoergai block. In addition, the crust–mantle ductile shear zone under the Longmen Mountains tectonic belt is the main fault, whereas the Beichuan–Yingxiu and Anxian–Guanxian faults at the surface are earthquake faults. The Wenchuan Ms 8.0 earthquake might be attributed to the collision of the Yangtze block and the Qinghai–Tibet Plateau. The eastward obduction of the eastern edge of the Qinghai–Tibet Plateau and eastward subduction of its deeper part under the influence of the collision of the Indian, Pacific, and Philippine Plates with the Eurasia Plate might have caused the Longmen Mountains tectonic belt to cut the Moho and extend to the middle and upper crust; thus, creating high stress concentration and rapid energy release zone. 相似文献
18.
由于印度板块持续向北运动,引起青藏高原的挤出,并于中新世末引起华北地块的向东挤出。大约在7.3 Ma,太行山西侧渭河盆地唐县面首先解体,继而向北、向东发展;到5 Ma左右,太行山东麓断裂带的右行走滑,导致华北中部唐县面全面解体,形成多个太行山内部山间盆地,以及太行山西侧山西地堑系。这些断陷盆地的断陷幅度各不相同,太行山西侧山西地堑系断陷幅度较大,太行山内部山间盆地断陷幅度较小,太行山东部的渤海湾盆地断陷活动不明显。伴随着盆地的形成,太行山相对进入快速隆升阶段。山西地堑系控盆断裂以及太行山东麓断裂带第四纪以来仍存在明显活动,切割并控制第四系,局部在地表形成地裂缝。华北地块中部的应力场恢复以及深部构造分析表明,深部地幔上涌对浅部伸展构造的形成具有重要的影响,深部构造演变与浅部构造演变具有高度的一致性和耦合性。太行山东部渤海湾盆地自中新世以来就进入拗陷阶段,断裂活动弱,构造演化与西侧差异较大,表明这期构造运动动力源于西侧,太行山东麓断裂带作为两侧差异演变的边界,调节着两侧的差异构造活动。 相似文献
19.
DONG Shuwen ZHANG Yueqiao WU Zhenhan YANG Nong MA Yinsheng SHI Wei CHEN Zhengle LONG Changxing AN Meijian 《《地质学报》英文版》2008,82(5)
An earthquake of Ms 8 struck Wenchuan County,western Sichuan,China,on May 12~(th), 2008 and resulted in long surface ruptures (>300 km).The first-hand observations about the surface ruptures produced by the earthquake in the worst-hit areas of Yingxiu,Beichuan and Qingchuan, ascertained that the causative structure of the earthquake was in the central fault zones of the Longmenshan tectonic belt.Average co-seismic vertical displacements along the individual fault of the Yingxiu-Beichuan rupture zone reach 2.5-4m and the cumulative vertical displacements across the central and frontal Longmenshan fault belt is about 5-6 m.The surface rupture strength was reduced from north of Beichuan to Qingchuan County and shows 2-3 m dextral strike-slip component.The Wenchuan thrust-faulting earthquake is a manifestation of eastward growth of the Tibetan Plateau under the action of continuous convergence of the Indian and Eurasian continents. 相似文献