内蒙古狼山地区南北向断裂构造应力场特征及其与区域构造演化关系

内蒙古狼山地区断裂构造十分复杂,主要发育有南北、东西、北东和北西走向的断裂构造.从南北向断裂的几何形态、运动性质、构造应力场特征入手进行研究,结合野外实地调查与测量,运用极射赤平投影方法,求出构造应力场的主应力轴方位,进而对本区的构造演化进行了探讨.初步认为,研究区发育的近南北向断裂至少受到过两期构造应力场的作用,第一期是在晚二叠世,由于华北克拉通向北、西伯利亚板块向南活动而形成碰撞拼贴运动所产生的近南北向近水平挤压构造应力场,此时构造应力场的主应力轴σ₁为北偏东10°左右,向北倾伏,倾伏角为15°~20°.在这一期构造应力场的作用下,狼山地区发育了一套破裂系统,它们分别表现为近东西走向的挤压构造带和逆断层、近北东走向的以左行为主的走滑断层、近北西走向的以右行为主的走滑断层以及近南北走向的张性断层.这些早期的断裂系统也制约着该区域后来的构造活动,第二期构造应力场是侏罗纪以来古太平洋板块向亚洲大陆俯冲而产生的.此构造应力场的主应力轴σ₁为北西-南东向,倾伏向为150°左右,倾伏角为10°~20°.第二期构造应力场的作用,使早期南北向断裂由原来的张性破裂面转为左行走滑,早期东西向断裂转为右行走滑,早期北东向左行滑动面转为压性面和褶皱轴方向,而早期的北西向破裂面则转为张性破裂性质.      

2019年5月18日松原M5.1地震构造机制分析

基于区域地震台网的数字化波形资料,使用ISOLA方法对2019年5月18日吉林松原M5.1地震进行矩张量反演,研究地震的震源机制,并且收集了地震序列中M_L2.5以上地震的震源机制解,采用FMSI（focal mechanism stress inversion）方法反演震中区构造应力场。结果显示：松原M5.1地震的矩震级为4.9,矩心深度为6 km,双力偶分量为91.5%,主压应力P轴方位角、倾角分别为76°和3°,主张应力T轴方位角、倾角分别为166°和16°,震源机制解显示典型的构造地震特征;震中区构造应力场理论应力轴σ₁方位角、倾伏角分别为88.0°和0.9°,σ₂方位角、倾伏角分别为178.2°和9.6°,σ₃方位角、倾伏角分别为352.5°和80.4°,这一结果与区域构造应力场一致。推断认为区域构造应力场触发了2019年松原M5.1地震活动,地震震源机制解的北西向节面与震中区附近的第二松花江断裂现今活动性质完全一致,认为第二松花断裂可能是松原M5.1地震的发震断层。     

青藏高原中部的东西向扩张构造运动

系统分析了1933~2003年间青藏高原及其周缘发生的745个中、强地震的震源机制解,研究了高原地壳构造运动及其动力学特征。结果表明,大量正断层型地震集中发生在青藏高原中部海拔4000m以上的地区,其中许多地震是纯正断层型地震。震源机制结果显示,该区正断层型地震的断层走向多为南北方向,断层位错矢量的水平分量均位于近东西方向,这表明青藏高原高海拔地区存在着近东西方向的扩张构造运动。地震震源应力场的研究结果表明,在高原中部高海拔地区,E-W向或WNW-ESE向的水平扩张作用控制着该区的地壳应力场。青藏高原高海拔地区近东西方向的扩张构造运动是该区引张应力场的作用结果,其动力学原因可能与持续隆升的高原自重增大引起的重力崩塌及其周边区域构造应力状况有关。而青藏高原周缘地区,除了东部边缘外,南部的喜马拉雅山前沿以及青藏高原的北部、西部边缘所发生的绝大部分地震都是逆断层型或走滑逆断层型地震。在青藏高原周缘地区,北东或者北北东方向水平挤压的构造应力场为优势应力场。在中国西部的大范围内,主压应力P轴水平分量位于NE-SW方向,形成了一个广域的NE-SW方向的挤压应力场。青藏高原及其周缘应力场特征表明,印度板块的北上运动以及它与欧亚板块之间的碰撞所形成的挤压应力场是高原强烈隆起的直接原因。在青藏高原中南部形成了近东西向引张应力场为主的区域,并以东西向扩张构造运动部分释放其应力积累。研究高原高海拔地区的引张应力场和近东西向扩张构造运动的特征,对于认识青藏高原强烈隆起的地球动力学过程与机制,有着重要的理论意义。     

青藏高原及其周围地区区域应力场与构造运动特征

本文系统解析并分析了1931年8月-2005年10月期间青藏高原及其周围发生的905个震级M4．5-8．5地震的震源机制结果,研究了青藏高原岩石圈的区域应力场与构造运动特征。结果表明,来自印度板块的北北东或北东方向的水平挤压应力控制了青藏高原及其周缘地区的岩石圈应力场。从喜马拉雅到贝加尔湖以南包括中国西部的广大范围内,主压应力P轴的水平分量位于近NE-SW方向,形成了一个广域的NE-SW方向的挤压应力场。特别是青藏高原周缘地区,除其东部边缘外,南部的喜马拉雅山前沿以及青藏高原的北部、西部边缘地区所发生的绝大部分地震都属于逆断层型或走滑逆断层型地震,表现出周缘地区的水平挤压应力更为强势。应力场特征充分表明, 印度板块的北上运动,以及它与欧亚板块之间的碰撞,所形成的挤压应力场是青藏高原强烈隆起的直接原因。在青藏高原周缘地区受到强烈挤压应力场控制的同时,有大量正断层型地震集中发生在青藏高原中部海拔4000m以上的地区,其中许多地震是纯正断层型地震。震源机制结果显示,近E-W向或WNW-ESE向的水平扩张应力控制着该区的岩石圈应力场;正断层型地震的断层走向多为南北方向,断层位错矢量的水平分量大体位于近东西方向。这表明青藏高原中部高海拔地区存在着近东西方向的扩张构造运动,且扩张构造运动是该区引张应力场的作用结果。其动力学原因可能与持续隆升的高原自重增大引起的重力崩塌及其周边区域构造应力状况有关。研究青藏高原存在挤压应力场与引张应力场及其构造运动的区域特征,对于认识青藏高原形成、发展的地球动力学机制,有着极其重要的意义。     

中国岩石圈应力场与构造运动区域特征

笔者系统分析了1918—2005年间中国大陆及其周缘发生的3130个中、强地震的震源机制解,根据其特征进行了岩石圈应力场构造分区,首次得到区域应力场的压应力轴和张应力轴空间分布的统计数字结果。在此基础上研究了应力场的区域特征、探讨了其动力学来源以及构造运动特征。总体结果表明,中国大陆及其周缘岩石圈应力场和构造运动可以归结为印度洋板块、太平洋板块、菲律宾海板块与欧亚板块之间相对运动,以及大陆板内区域块体之间的相互作用的结果。印度洋板块向欧亚板块的碰撞挤压运动所产生的强烈的挤压应力,控制了喜马拉雅、青藏高原、中国西部乃至延伸到天山及其以北的广大地区。在青藏高原周缘地区和中国西部的大范围内,压应力P轴水平分量方位位于20～40°,形成了近NE方向的挤压应力场。大量逆断层型强震集中发生在青藏高原的南、北和西部周缘地区,以及天山等地区。而多数正断层型地震集中发生在青藏高原中部高海拔的地区,断层位错的水平分量位于近东西方向。表明青藏高原周缘区域发生南北向强烈挤压短缩的同时,中部高海拔地区存在着明显的近东西向的扩张运动。中国东部的华北地区受到太平洋板块向欧亚板块俯冲挤压的同时,又受到从贝加尔湖经过大华北直到琉球海沟的广阔地域里存在着的统一的、方位为170°的引张应力场的控制。华北地区大地震的震源机制解均反映出该区地震的发生大体为NEE向挤压应力和NNW向张应力的共同作用结果。台湾纵谷断层是菲律宾海板块与欧亚板块之间碰撞挤压边界。来自北西向运动的菲律宾海板块构造应力控制了从台湾纵谷、华南块体,直到中国南北地震带南段东部地域的应力场。地震的震源机制结果还表明,将中国大陆分成东、西两部分的中国南北地震带是印度洋板块、菲律宾海板块与太平洋板块在中国大陆内部影响控制范围的分界线。     

四川盆地南部地震区发震构造及其新构造背景

近10年以来,在四川盆地南部的川黔滇交界地区发生了一系列中、强地震,其发震机理引起了广泛的关注和讨论。本文基于历史地震震中分布和区域活动断裂构造编图,发现四川盆地南部地震主要集中在4个地震亚区,分别为马边—永善、鲁甸、长宁和自贡—荣昌等地震亚区,华蓥山断裂带西南段是其中一条重要的地震构造边界带。通过综合分析主、余震分布特征、震源深度和震源机制解等资料,认为该地震区存在2类发震断层,其中马边—永善、鲁甸、长宁地震亚区以基底断层走滑型或走滑逆冲型地震为主,而自贡—荣昌亚区则以浅层滑脱断层逆冲型地震为主。区域挤压应力方向从WNW ESE向至ENE WSW向。双震型地震频发,一次走滑地震往往会触发一组共轭基底断层的同时活动。这些地震构造特征表明它们不同于盆地西缘的龙门山—岷山逆冲走滑型地震构造带,也不同于鲜水河—安宁河—小江走滑型地震构造带,属于一个新生的克拉通地震构造区,因西南扬子地块遭受青藏高原的向东推挤和压迫,构造应力通过“大凉山地块”传递并作用到四川盆地南部,导致扬子地块的断块型结构及其基底断层的逆冲走滑活动,进而主导了该地区的一系列中、强地震的破裂事件。     

新城金矿主成矿期构造应力场对矿体倾伏、侧伏、富矿柱的控制及成矿深度的估算

成矿构造应力场研究是控矿构造研究、认识矿体空间展布形态、位置、预测及布置探矿设计的基础。依据弹性力学和莫尔库仑剪切破裂理论,推导出形成共轭及在剪切构造带内形成羽列、雁列等构造应力场的产状和形成羽列、雁列主应力大小的数学解析表达式,进而应用计算机对新城金矿床主矿体进行了测算。结果显示：该矿主容矿构造是在NNW向缓倾拉张主应力、NE向陡倾主压应力、焦家构造带平面呈右行扭动下形成的。NWW向中间主应力控制新城Ⅰ号主矿体在NW向倾斜平面上延深的长轴方向。该轴在水平面上投影的倾伏向为281°,与水平面的夹角倾伏角为26°,在N40°E纵投影面上向SW侧伏,侧伏角为45°,富矿柱产状亦与中间主应力轴产状一致。在已获取容矿构造产状基础上,据相关岩石力学性质测试成果,分析并建立了主容矿羽列与控制剪切构造带两者的力学关系和剪切破裂方程式。联立解出成矿应力场的最大和最小主应力的量值,再由陡倾主应力大小估算出该矿头部的成矿深度在2 750 m左右。     

新城金矿主成矿期构造应力场对矿体倾伏、侧伏、富矿柱的控制及成矿深度的估算

成矿构造应力场研究是控矿构造研究、认识矿体空间展布形态、位置、预测及布置探矿设计的基础。依据弹性力学和莫尔库仑剪切破裂理论,推导出形成共轭及在剪切构造带内形成羽列、雁列等构造应力场的产状和形成羽列、雁列主应力大小的数学解析表达式,进而应用计算机对新城金矿床主矿体进行了测算。结果显示：该矿主容矿构造是在NNW向缓倾拉张主应力、NE向陡倾主压应力、焦家构造带平面呈右行扭动下形成的。NWW向中间主应力控制新城Ⅰ号主矿体在NW向倾斜平面上延深的长轴方向。该轴在水平面上投影的倾伏向为281°,与水平面的夹角倾伏角为26°,在N40°E纵投影面上向SW侧伏,侧伏角为45°,富矿柱产状亦与中间主应力轴产状一致。在已获取容矿构造产状基础上,据相关岩石力学性质测试成果,分析并建立了主容矿羽列与控制剪切构造带两者的力学关系和剪切破裂方程式。联立解出成矿应力场的最大和最小主应力的量值,再由陡倾主应力大小估算出该矿头部的成矿深度在2 750 m左右。     

2019年四川长宁MS6.0地震的地质构造成因——区域性构造节理贯通、破裂结果

根据野外地质调查结果并结合区域地质资料, 对2019年长宁MS6.0地震震区的地质背景和新构造运动特征进行分析后, 讨论了此次地震的发震构造并给出该地区孕震模型。基于区域地质与地震资料, 结合地表调查结果发现, 该区的新构造运动具有间歇性整体弱隆升、断裂晚第四纪活动不明显以及地震活动相对微弱等特征。此次强震的仪器震中位于长宁双河大背斜的西段, 该背斜经历了古老的NE向挤压应力场和顺时针旋转应力场的双重叠加构造作用。在大背斜的核部和翼部普遍发育了两组NW向节理和一组NE向节理, 并显示出区域性分布特征, 构成了具一定规模的构造破碎带(软弱带)。地震记录显示, 此次强震的地震序列呈现出明显的NW向线性条带, 震源机制解主要指示了NEE—NE向水平挤压应力作用的结果。结合地表构造特征可进一步推断, 长宁地震的震源破裂型式是以沿NW向破裂面发生以逆冲为主兼具左旋走滑分量的破裂过程为特征。综合分析认为, 2019年长宁MS6.0地震可能是双河背斜中的赋存超压环境叠加NE向古构造应力场和旋转应力场作用, 导致区域性NW向纵向节理发生构造强化、贯通, 并进一步破裂的结果。     

中国东部海域及其邻区现代构造应力场研究

中国东部海域是指渤海、黄海和东海地区。前人利用震源机制解、井壁崩落和水压致裂等资料,分别对有关海区的现代构造应力场作过不同程度的研究。文中根据前人的工作并结合海陆地区新构造运动及其动力条件分析,对东部海域及邻区的现代构造应力场进行较深入的研究。该区现代构造应力场以水平至近于水平挤压作用为主要特征,压应力方向从北到南由NE逐渐转为NEE、EW、SEE至SE向,总体呈向东发散的扇形分布。构造应力作用强度具有非一致性,北强南弱。海域具有与大陆统一的现代构造应力场,相应可划为东北、华北和华南3个应力区。中国东部大陆和海域在青藏高原东部被印度板块挤出的构造块体往NE-SE方向滑动推挤及东边太平洋和菲律宾海板块向NWW俯冲推挡的共同作用下,形成现代构造应力场,且青藏高原东部被挤出块体东向滑动的推挤是现代构造应力场产生的主要动力。     

Understanding of Petobo liquefaction flowslide by 2018.09.28 Palu-Donggala Indonesia earthquake based on site reconnaissance

Landslides - The Palu-Donggala earthquake struck Palu city of Sulawesi island, Indonesia, on 28 September 2018. A large-scale liquefaction phenomena occurred in some areas which caused massive...     

Study on potential tsunami by earthquake in subduction zone of Sulawesi Sea

Indonesia is one country in the world featuring a complex tectonic structure. This condition makes earthquakes often occur in many areas of this country and as an earthquake rages beneath the sea, it will potentially trigger tsunami. One of the areas in Indonesia with a high seismic activity is Sulawesi region particularly in the Sulawesi Sea subduction zone, making it important to carry out a study on the potential tsunami at this location. The purpose of this study was to analyze the existing huge potential energy in Sulawesi Sea subduction zone and to identify tsunami modeling likely to occur based on the potential energy of the region. The approach used in assessing the tsunami disaster was the calculation of the potential energy of an earthquake and tsunami modeling based on the potential energy. The method used in this research was the least squares method for the calculation of potential energy, and near-field tsunami modeling with the assistance of TUNAMI-N2 COD. The research finding has shown that the Sulawesi Sea subduction zone has potential energy of 1.35469?×?10²³ erg, equivalent to an earthquake with a magnitude of 7.6 Mw. The tsunami modeling made shown the average wave propagation reaching ashore within 12.3 min with a height varying between 0.1 and >?3 m. The tsunami modeling also indicated that there are seven sub-districts in Buol District, Central Sulawesi, which is affected by a significant tsunami.     

Past and present geotectonic position of Sulawesi, Indonesia

Sulawesi with its peculiar K-shaped pattern is situated in an area where the Eurasian, Indian—Australian and Pacific plates interact and collide.Complex geological processess in this area resulted in the transformation of a normal island-arc structure into an inverted one, deformation of an already tectonized belt, sweeping of fragments against unrelated terrain, thrusting of oceanic and mantle material over the island arc, closing of deep-sea basins behind the arc, trapping of old oceanic crust caused by the rolling up of an island arc, formation of a marginal basin by the spreading of the sea floor behind the arc, development of small subduction zones with reverse polarities etc.Small deep-sea basins surrounding Sulawesi such as the Gulf of Bone and the Gulf of Gorontalo originally formed the arc—trench gap of the Sulawesi island arc.The Banda Sea is considered as an oceanic crust trapped by the bending of the east—west trending Banda arc due to the northward drift of Australia combined with the westward movement of the Pacific plate. Similarly the Sulawesi Sea consists of an old Pacific crust trapped by the westward bending of the Sulawesi island arc, caused by the spearheading westward thrust along the Sorong transform-fault system, in which later a minor spreading center became active in its central part. The Molucca Sea comprises tectonic mélange in which presumably a small spreading center developed between the two colliding arcs of northern Sulawesi and western Halmahera. While the Benioff zones dip under the northern Sulawesi and Halmahera arcs in normal fashion, the mélange thrusts over them. The Strait of Makassar is a marginal basin which was brought into existence by the spreading of the sea floor between Kalimantan and Sulawesi.The evolution of Sulawesi started in Miocene time or even earlier when 800 km east of Kalimantan a north—south trending east-facing island arc came into existence, originating from a spreading center located in the Pacific Ocean. Volcanism and plutonism accompanied this subduction process.Collision between Sulawesi and the Australian—New Guinea plate which occurred in early Pliocene time severely transformed Sulawesi into an island with its convex side turned towards the continent, at the same time causing obduction of ophiolite in the eastern arc of this island.The movement of the Pacific plate continued and gradually pushed Sulawesi towards the Asian continent, resulting in the closing of the sea between Kalimantan and Sulawesi islands separated by small straits and deep seas resembling the complicated pattern of the Philippine Archipelago, in which the original double island-arc structure can no longer be recognized.     

Numerical modeling of Late Miocene tectonic inversion in the Xihu Sag,East China Sea Shelf Basin,China

The East China Sea Shelf Basin is an important oil- and gas-bearing basin in the West Pacific continental margin. This region was affected by subduction of the Pacific Plate and the Philippine Plate in Cenozoic and experienced multi-stage tectonic inversions. This paper presents results from a numerical simulation by finite element method to the Xihu Sag in the East China Sea Shelf Basin and neighboring areas in an attempt to evaluate the WNW-directed compression on the sag during Late Miocene. Based on comprehensive structural analysis of a large number of seismic profiles, we determine the structural geometry of the sag, including the basement of the basin, the sedimentary cover, and 29 major faults in the Xihu Sag. Simulation results show that under continuous WNW-directed compression, tectonic inversion occurred firstly in the Longjing and Yuquan tectonic zones in the sag. Based on quantitative analysis of vertical displacement field of the Xihu Sag and peripheral areas and its stress intensity evolution, we identify a compressional regime in the Longjing Anticline Zone with a gradually propagated uplifting from south to north; whereas the propagation of uplifting in the Yuquan Anticline Zone is from north to south. The inversion intensity decreases from north to south. The formation of the tectonic inversion zone in the Xihu Sag is not only correlated to the direction of compression and fault patterns in the basin, but also closely related to the spatial configuration of fault surfaces of the Xihu–Jilong Fault in the Xihu Sag.     

论日本海区深震等深线凸进方向的动态变化及其在地震预报中的意义

深震等深线加深的梯度方向,反映了板块插入方向和板块俯冲力作用的主体方向;等深线凸进方向的动态变化,反映了贝尼奥夫带的偏转;日本海深源地震和我国东部地区浅震的个体(强震)和群体迁移,反映了深、浅部应力场强区的转移。这种转移的深层原因,可能与上地幔物质流流动方向变化有关。强区范围的圈定和转移规律,对地震的地点预报,具有重要意义。     

New data on mantle seismicity of the Caspian region and their geological interpretation

The results of detailed seismological observations with bottom recording systems carried out in 2004 and 2006 near the Dagestan coast of the Middle Caspian are considered. The records of more than 550 micro- and weak earthquakes with M_L = 0.1–4.7 (M_LH = ?0.7 to 4.3) were obtained during 165 days of recording; a fifth of these earthquakes occurred in the upper mantle at a depth of 50–200 km. Over the entire period of instrumental recording since the 1930s, only 10 mantle earthquakes with M_LH = 3.5?6.3 have been recorded by on-land systems. The highest density of earthquake epicenters with source depths down to 50 km is established on the Middle Caspian coast between Derbent and Izberbash and in the adjacent water area. The mantle earthquakes with hypocenters at a depth of 60–80 km cluster beneath the western wall of the Derbent Basin, whereas deeper hypocenters are located beneath both the wall of this basin and the Middle Caspian coast. The sporadic mantle earthquakes recorded in 2004 (about 30 shocks), determined by a network of systems with a small aperture, depicted a zone plunging beneath the Greater Caucasus with indications of a peculiar “subduction” of the Scythian Plate beneath the Caucasus. Subsequent observations based on a more extensive network were carried out in 2006. They substantially changed the pattern of mantle earthquake hypocenters. According to this evidence, the sources of mantle earthquakes make up a dispersed cloud extended in the vertical direction beneath the Middle Caspian coast and water area, which may be regarded as a relic of tectonic activity of a bygone tectonic epoch. A comprehensive tectonic interpretation of the detected seismological phenomenon is given.     

大南海地区新生代板块构造活动

在新生代澳大利亚板块和欧亚板块之间的大洋中，存在一些地块(微板块)；同时，澳大利亚板块北部边缘的一些地块先后和澳大利亚板块分离，向北运动，与一些和欧亚板块分离出来的地块先后发生碰撞缝合。在此期间，由于地块分离而发生海底扩张，产生许多小洋盆，如南海、苏录海、苏拉威西海、安达曼海等，最后形成了东南亚地区今日的构造景观。笔者从大南海地区新生代的构造演化史之框架来研究南海地区新生代的构造演化历史，认为南海地区新生代的构造活动既与印度板块和欧亚板块的碰撞有关，也与太平洋板块向欧亚板块的俯冲活动有联系；同时，还受到澳大利亚板块向北运动之影响。南海地区在新生代发生过两次海底扩张，第一次海底扩张发生在42～35Ma前．是受印度板块和欧亚板块碰撞而引起欧亚大陆之下向东南方向之地幔流的影响而发生的，其海底扩张方向为NWSE，产生了南海西南海盆；第二次海底扩张发生于32～17Ma前。由于太平洋板块向欧亚板块俯冲，俯冲的大洋岩石圈已达700km深处，阻挡了欧亚大陆的上地幔向东南方向之流动，从而转向南流动。引起南海地区南北向海底扩张，即新生代第二次海底扩张，产生了南海中央海盆。南海新生代洋盆诞生之后，由于大南海地区继续有地块碰撞和边缘海海底扩张，对南海南部地区产生挤压，从而使这里的沉积发生变形，这就引起万安运动(南海南部)。     

Late Cretaceous-Paleogene deepwater basin of North Afghanistan and the Central Pamirs: Issue of Hindu Kush earthquakes

The within-Iranian backarc basins, including the largest Sebzawar Basin, opened in the Mid-Cretaceous. Spreading in this basin was completed by the end of the Cretaceous. The basin closed in the Eocene with the formation of subduction zones and volcanic-plutonic belts. Data on North Afghanistan and the Central Pamirs have allowed us to reconstruct the eastern continuation of the Sebzawar Basin up to the west of the Central Pamirs. No fragments of oceanic crust are retained in Afghanistan and the Pamirs, but by analogy with the Sebzawar Basin, thick Paleogene flysch sequences and volcanic-plutonic complexes indicate setting of the active margin and subduction. It is suggested that the belt of mantle seismicity that extends for 550 km to the south of the Central Pamirs is related to the plunging and deformation of the lithosphere once underlying the Cretaceous-Paleogene basin. The extremely vigorous seismicity of the Hindu Kush megasource at the western termination of the seismic belt is caused by a number of specific tectonic features that predetermined the early onset of plunging of the subducted sheet (slab). In the megasource, the slab sank to a depth of 300 km and became vertical; its active deformation has proceeded up to the present. In the eastern part of the seismic belt, the slab started to plunge much later and therefore has retained a gentle slope, so that the depth of the hypocenters is shallower (down to 200 km), and earthquakes are less strong.