新加坡地应力测量

2008年和2009年, 通过和新加坡宜康地质技术有限责任公司合作, 在新加坡18个浅钻孔中进行了水压致裂地应力测量. 通过测量获得了新加坡地壳浅部的现今应力状态, 为新加坡拟建地下管缆隧道设计施工提供了地应力依据, 也为世界应力环境数据库提供了参考. 测试结果表明, 在38.00~56.95 m深度域内最大水平主应力σ_h值为3.45~9.64 MPa, 最小水平主应力σ_h为2.49~6.28 MPa. 水平主应力和用上覆岩层重量计算的垂直应力σv之间的关系为σ_h>σ_h>σv,最大、最小水平主应力平均值分别是垂直应力平均值的5.13倍和3.23倍, 表明新加坡应力场以水平应力为主导. 初步分析认为, 新加坡陆域浅部构造应力场的量值大致呈南、北两端偏低, 中间高的态势, 在北端最大与最小水平主应力值都小于它们各自的平均值, 而南端则与平均值相当. 最大水平主应力优势方向为NE—NEE向, 该方向与前人在其邻区获得的构造应力场方向和由震源机制解反映的主压应力方向较为一致. 新加坡现今构造应力场状态与印度板块、澳大利亚板块、菲律宾板块与欧亚板块的汇聚作用有着密切的联系. 根据库仑摩擦滑动准则, 断层面摩擦系数取0.6~1.0, 分析了研究区内断层产生摩擦滑动的可能性.     

Characteristics of present-day active strain field of Chinese mainland

On the basis of the GPS data obtained from repeated measurements carried out in 2004 and 2007,the horizontal principal strain of the Chinese mainland is calculated,which shows that the direction of principal compressive strain axis of each subplate is basically consistent with the P-axis of focal mechanism solution and the principal compressive stress axis acquired by geological method.It indicates that the crustal tectonic stress field is relatively stable in regions in a long time.The principal compressive stress axes of Qinghai-Tibet and Xinjiang subplates in the western part of Chinese mainland direct to NS and NNE-SSW,which are controlled by the force from the col-lision of the Eurasia Plate and India Plate.The principal compressive strain axes of Heilongjiang and North China subplates in the eastern part direct to ENE-WSW,which shows that they are subject to the force from the collision and underthrust of the Eurasia Plate to the North America and Pacific plates.At the same time,they are also af-fected by the lateral force from Qinghai-Tibet and Xinjiang subplates.The principal compressive strain axis of South China plate is WNW-ESE,which reflects that it is affected by the force from the collision of Philippine Sea Plate and Eurasia Plate and it is also subject to the lateral force from Qinghai-Tibet subplate.It is apparent from the comparison between the principal compressive strain axes in the periods of 2004～2007 and 2001～2004 that the acting directions of principal compressive stress of subplates in both periods are basically consistent.However,there is certain difference between their directional concentrations of principal compressive stress axes.The sur-face strain rates of different tectonic units in both periods indicate that the events predominating by compressive variation decrease,while the events predominating by tensile change increase.     

Tectonic stress field in East Eurasia

The overall pattern of the recent tectonic stress field in the eastern part of the Eurasian plate is inferred from the geological features of large transcurrent and reverse faults, graben structures and from focal mechanism solutions of shallow earthquakes. NE-SW striking trajectory lines, of maximum horizontal tectonic stress axis (σ Hmax), are estimated at the north of Tibet and mainland China, but its strike turns to easterly near the eastern margin of the Eurasian plate. This suggests that the main origin of the σ Hmax in East Eurasia is due to a compressive stress regime along, the Himalayan belt, Tibet and the Japan Trench (and also the Sakhalin and Nankai Trough). This tectonic stress field seems to provide some influence on the extensional tectonics in the Shansi region, Baikal, and also in the Okinawa Trough where the N-S opening has been confirmed. The systematic view of the tectonic stress field in East Eurasia, makes it possible to appreciate the fundamental background of a number of complicated intra-plate tectonics.     

Geological analysis and physical modeling of structural pumping in high effective formation of Kela 2 gas field

In a 3-D closed geological body, in case “structural expanding” inside is induced by stress, it can produce the pressure difference between the expanding cell and surrounding rock, then generate a pumping force directed toward the cell and accelerate the directional flow of fluid in the strata. The structural style and conditions of gas reservoir-formation in the Kuqa depression are favorable to the structural pumping. According to similarity principle, a physical modeling of structure formation and gas filling process of the Kela 2 gas field has justified the occurrence of structural pumping and its important role in gas-reservoir formation with high efficiency under the compressive and well-sealed circumstance. Therefore, authors propose that structural pumping is an important mechanism of gas reservoir-formation with high efficiency in the Kuqa depression.     

中国大陆现今地应力场黏弹性球壳数值模拟综合研究

中国大陆现今实测地应力场的状态与板块构造环境、活动断裂带分布、地形地貌以及地壳结构呈现一定相关性. 在中国大陆西缘,印度洋板块与欧亚板块陆发生陆碰撞,在中国大陆东缘,菲律宾海板块、太平洋板块俯冲到欧亚板块之下. 中国大陆内部被大型活动断裂带分割为多个块体,各个块体的地壳结构和厚度呈不均匀分布,地形地貌起伏具有很大的差异. 笔者以中国大陆块体模型为基础,把板块构造作用和重力势作为主要影响地应力状态的两个主要要素,在现今活动构造、GPS和实测地应力等成果的约束下,利用线性黏弹体球壳有限元模拟分析了中国大陆现今地应力场的分布特征和控制因素. 结果表明: (1)构造应力场总体上呈现出西部挤压,东部拉张的特征,印度板块与欧亚板块的持续碰撞形成了青藏高原及其周缘的挤压性质的构造应力场,而东部菲律宾板块与太平洋板块的俯冲形成了黄海、东海和环渤海区域的拉张性质的构造应力场,中间为拉张环境和挤压环境的过渡,最大主应力的方向受到板块构造环境和活动构造分布的控制;(2)重力的影响主要体现在地形梯度大和地壳厚度结构变化大的地壳浅部区域,在藏南、滇西北局部地区的地壳浅部由于受到重力势控制,呈现为张性应力场,在塔里木地区由于重力势引起的应力场与构造应力场同为挤压性质,因此该区的挤压强度得以增加;(3)中国大陆浅部地应力场的状态主要受到区域板块构造环境、块体边界活动构造带的展布和地形的控制,总体上以南北构造带为界,西部以较强的压性构造环境为主,东部为较弱的压性构造环境,藏南和滇西北局部地区存在有张性构造环境;构造应力对地应力的贡献比重随着深度增加而增加;(4)采用黏弹性模型的构造应力场模拟结果比完全弹性模型的模拟结果能够更好地与实测地应力场相吻合,利用完全弹性模型分析由地震等诱发的地应力瞬时变化是有效的;(5)青藏高原东南缘最大主应力方向发生了较大的偏转,其主要控制因素有:印度板块持续的碰撞、中下地壳对上地壳拖曳以及印度板块通过实皆断裂对欧亚板块的剪切拉伸作用. 中国大陆现今地应力场是整个地壳岩石黏弹特性长期演化和断裂活动的结果,是地应力场动态演化过程中在现今时间点上的状态,受到板块构造环境、大陆内部活动断裂分布、地形地貌和地壳结构等因素不同程度的控制,模拟结果为中国大陆地应力场提供了一个定量的参考模型.     

郯庐断裂带鲁苏皖段构造应力场及分段特征研究

利用Snoke方法求解和收集得到的77次中小地震的震源机制解资料, 采用Gephart应力张量反演方法, 获得了郯庐断裂带鲁苏皖段构造应力场, 最大主压应力方位角为80°, 最小主压应力方位角为172°, 最大、 中等和最小主压应力倾角分别为15°、 65°和19°, 反映了研究区处于近EW向水平作用和近NS向的水平拉张作用环境下。 根据地震活动、 地质构造及震源机制解差异, 我们将郯庐断裂带鲁苏皖段分5个区段开展研究, 结果显示: 5个分区应力场存在局部差异, 最大主压应力方位角处于63°～88°之间, 从北往南总体方向成顺时针偏转的趋势。 跨郯庐断裂带两侧的应力场研究结果显示, 从西到东最大主压应力方向有一个逆时针偏转的趋势, 西侧最大主压应力方向更接近EW向, 东侧更接近NE向, 郯庐断裂带内处于两侧的过渡地段。     

清江大龙潭水库区新生代以来地壳应力场特征

根据震旦－第三纪地震中构造变形的实际观测及卫星影象解译资料,计算了清江大龙潭水库区新生代以来区域应力场的主应力方向。结果表明：主压应力为北东东向,主张应力为北北西向;现代构造应力场与新生代以来应力场基本一致;晚第三纪以来,该区构造应力场相对稳定和统一。     

欧亚地震带现代构造应力场及其分区特征

利用美国哈佛大学矩心矩张量目录中的2818个地震的震源机制解资料,分析了欧亚地震带及其5个分区现代构造应力场的基本特征,给出了5个分区的震源机制主压应力方向分布图。结果表明:①欧亚地震带以逆断型和走滑型断层活动为主;②地中海地震区以走滑断层活动为主,主压应力方向为SSW向;③伊朗—阿富汗—巴基斯坦地震区以逆断型断层活动为主,主压应力优势方向为NNE—NS向;④喜马拉雅地震以逆断型为主,主压应力优势方向为NS和NE向;⑤川—滇—缅地震区以走滑断层活动为主,主应力场方向为NNE向;⑥印度尼西亚地震区以逆断型断层活动为主,主压应力优势方向为NE—SSW向。各分区的主压应力方向明显受其所在区域板块运动的影响,由此推测板块运动可能是产生欧亚地震带构造应力的主要力源。     

龙首山地区构造应力场初步探讨

讨论了沟谷成因与构造应力场的关系,利用沟谷资料计算了龙首山地区的主压应力方向,结果表明,主压应力为北东向。新构造应力场、现代构造应力场、地震应力场趋于一致。认为晚第三纪以来,龙首山地区地壳构造应力场相对稳定,应该是青藏地块与阿拉善地块相互作用的结果。     

长江三峡地区新生代以来地壳应力场的基本特征

根据白垩－第三纪红层中构造变形实际观测及水系统计资料，计算了三峡地区新生代和新构造期分区及区域应力场的主应力方向。结果表明：方压应力为北东东向，主张应力为北北西向，现代构造应力场与新生代以来应力场基本一致。     

Depositional sequence architecture and filling response model of the Cretaceous in the Kuqa depression, the Tarim basin

The Cretaceous system of the Kuqa depression is a regional scale (second order) depositional sequence defined by parallel unconformities or minor angular unconformities. It can be divided into four third-order sequence sets, eleven third-order sequences and tens of fourth- and fifth-order sequences. It consists generally of a regional depositional cycle from transgression to regression and is composed of three sets of facies associations: alluvial-fluvial, braided river-deltaic and lacustrine-deltaic facies associations. They represent the lowstand, transgressive and highstand facies tracts within the second-order sequence. The tectonic subsidence curve reconstructed by backstripping technique revealed that the Cretaceous Kuqa depression underwent a subsidence history from early accelerated subsidence, middle rapid subsidence and final slower subsidence phases during the Cretaceous time, with the correspondent tectonic subsidence rates being 30-35 m/Ma, 40-45 m/Ma and 5-10 m/Ma obtained from northern foredeep. This is likely attributed to the foreland dynamic process from early thrust flexural subsidence to late stress relaxation and erosion rebound uplift. The entire sedimentary history and the development of the three facies tracts are a response to the basin subsidence process. The slower subsidence foreland gentle slope was a favorable setting for the formation of braided fluvial deltaic systems during the late period of the Cretaceous, which comprise the important sandstone reservoirs in the depression. Sediment records of impermanent marine transgression were discovered in the Cretaceous and the major marine horizons are correctable to the highstands of the global sea level during the period.     

用滑动方向拟合法反演富蕴地震断裂带应力场

本文根据野外考察测得的1931年新疆富蕴8级地震形成的地震断裂带内42组断层水平和垂直位移数据,求得42个断层面上的滑动方向.利用滑动方向拟合法(使计算的断层面上的剪切力方向与观测的滑动方向之间夹角最小)求出了断裂带上由北向南四个区段的驱动断层滑动的平均应力场.结果表明,四个区段的最大和最小主压应力轴皆水平,最大主压应力轴方位大致在 N15E 至 N30E 之间.整个断裂带的应力场相当均一,这说明富蕴大地震的发震原因不象是局部因素,而可能是大范围构造运动的结果.      

北京地区地应力测量与主要断裂稳定性分析

2008年汶川地震后,为查明北京地区现今地应力状态、评价断裂稳定性,相继在北京地区开展了5个深孔（600~1000 m）的水压致裂法地应力测量,并在适宜深度安装了地应力相对变化监测探头,建立了地应力变化监测台站.本文首先利用实测地应力数据分析了北京地区地壳浅表层应力状态,结果表明：（1）北京地区千米深度内,最大、最小水平主应力随深度增加梯度系数分别为0.0328和0.0221,侧压系数K_av和K_Hv值,最大、最小水平主应力之比K_Hh值与国内外已有认识基本一致,而水平向剪应力相对强度参数μ_m值较低;（2）北京地区最大水平主应力优势方向为近EW向,与华北地区构造应力场方向基本一致,同时受区内断裂活动等影响,存在与区域主应力方向偏差的局部应力场;（3）实测数据揭示的应力结构显示,北京地区地壳浅表层最大主应力（σ₁）总体为最大水平主应力（σ_H）,受区域构造演化以及测点附近断裂的影响,中间主应力（σ₂）与最小主应力（σ₃）所对应的实测地应力存在变化,但总体来讲,实测地应力数据揭示的应力结构与北京地区主要断裂性质基本相吻合.其次,基于实测应力数据,采用库仑摩擦滑动准则,结合拜尔定律,并取摩擦系数为0.2~1.0,初步评价了北京地区主要断裂稳定性,结果显示：（1）在摩擦系数取0.6~1.0条件下,北京地区现今应力状态尚未达到导致断裂失稳滑动水平,断裂不会出现失稳滑动现象;（2）摩擦系数弱化到0.4时,西峰寺钻孔应力状态满足断裂失稳滑动条件,揭示出八宝山断裂存在失稳滑动可能性,而夏垫-马坊断裂和黄庄-高丽营断裂附近测点应力状态将趋近满足断裂失稳滑动条件,表明这两条断裂有趋向失稳滑动可能性;（3）只有当摩擦系数弱化到0.2时,北京地区主要断裂才可能在现今应力状态出现断裂失稳滑动.本文的认识对北京地区乃至华北地区构造应力场、地震地质研究有重要参考意义.     

The Yanshan orogeny and late Mesozoic multi-plate convergence in East Asia—Commemorating 90th years of the “Yanshan Orogeny”

The Yanshan movement/orogeny has been proposed for 90 years, which is of special significance in the history of geological research in China. This study conducted a review by synthesizing major achievements regarding episodic deformation features, sedimentary and magmatic records of the Yanshan orogeny in China, and clarified the episodic tectono-magmatism and its geodynamic origins. The tectonic implications of the Yanshan orogeny are discussed in the context of global plate tectonics and supercontinent reconstruction. Lines of evidence from structural, sedimentary and magmatic data suggest that the Yanshan orogeny represents a regional-scale tectonic event that affected the entire China continent in late Mesozoic period. Numerous age and structural constraints consistently indicate that the Yanshan orogeny was initiated in the Jurassic(at ～170±5 Ma). and was characterized by alternating stages of crustal shortening at ～170–136 Ma, crustal extension at ～135–90 Ma, and weak shortening at ～80 Ma. The 170–136 Ma crustal shortening was reflected in the generation of two regional stratigraphic unconformities(the Tiaojishan and Zhangjiakou unconformities), which were initially named the A and B episodes of "the Yanshan Orogeny" by Mr.Wong Wenhao in 1928. Geodynamically, the Yanshan orogeny in East Asia was associated with nearly coeval oceanic subduction and continental convergence in the Paleo-Pacific, Neo-Tethys, and Mongol-Okhotsk tectonic domains. As a consequence, three giant accretionary-collisional tectonic systems were formed along the continental margins of East Asia, i.e., the Mongol-Okhotsk, Bangonghu-Nujiang, and SE China subduction-and collision-related accretionary systems. The Yanshan orogeny induced widespread crustal-scale folding and thrusting, tectonic reactivation of long-lived zones of crustal weakness,and extensive magmatism and mineralization in intraplate regions. Based on the time principle of supercontinent assembly and break-up, we propose that the mid-Late Jurassic multi-plate convergence in East Asia might represent the initiation of the assembly of the Amasia supercontinent, and the Yanshan orogeny might be the first "stirrings" that is a prerequisite for the birth of the Amasia supercontinent.     

中国大陆及其周边地区应力场特征

本文收集了1976—2018年发生在中国大陆及其周边地区(15°~55°N, 65°~125°E)的4303个地震震源机制解, 分析了该区震源机制解和P、 T轴空间分布特征, 并使用这些震源机制解, 反演得到了中国大陆及周边地区二维构造应力场分布。 应力场反演结果表明, 云南大部、 青藏高原大部以及华北华南大部以走滑型应力性质为主, 印度洋板块与欧亚板块的强烈碰撞控制着中国西部地区, 大量的逆断型地震集中分布在青藏高原周缘和西域活动地块的天山地区。 青藏高原内部也存在正断型地震, 且应力场方向在26°N发生了很大的变化。 位于青藏高原东构造线以南的滇缅活动块体, 最大主压应力σ₁方向在大致100°E发生突变, 由以西的NNE方向偏转到NNW方向。 中国东部的东北块体到华北块体再到华南块体, 最大主压应力方向有一个从NE向逐渐转变成EW向再变化到NW向的旋转趋势。 应力场总体结果表明, 中国东部应力场主要受到太平洋板块和菲律宾板块对欧亚大陆俯冲的作用, 中国西部主要受印度板块向北碰撞欧亚大陆的影响, 块体内部相互作用、 块体与断裂带相互作用也对应力场变化产生影响。     

菲律宾海板块的整体旋转线性应变模型与板内形变-应变场

用菲律宾海板块上7个站ITRF2000的速度建立了菲律宾海板块的整体旋转线性应变模型. 结果认为菲律宾海板块的现今运动是顺时针方向旋转,与NNR_NUVEL_1A估计的旋转方向一致,但与NNR_NUVE_1A估计的旋转极位置和旋转角速度有较大差别. 本文模型与Sella等建立的刚体运动模型相比能更精确地描述菲律宾海板块的现今构造运动与板内形变. 菲律宾海板块内部存在强烈的形变-应变场. 在板块上存在一致的向东形变,形变速率在中央构造线附近小,东、西边界附近大,南、北两端小,中部大,在Mariana弧上向东的形变速率达到484 mm/a. 板块上南北方向的形变,东、西部存在明显差别,东部的南北向形变速率很小,西部在Manila海沟附近南北向形变速率较大,北端向北的形变速率为113 mm/a,南端向南的形变速率为293 mm/a. 板块的中央构造线把板块的主应变场分为东、西两个区. 东区存在非常强烈的张应变,压应变则很弱. 主张应变为近东西方向,从中央构造线向东主张与主压应变率逐渐增加,板块东南边界附近（148°E,15°N）主张应变率最大为858×10-8/a. 在西区,存在很强的主压应变而主张应变则较弱,主压应变为NW-SE方向,主压与主张应变率呈现从中央构造向西逐渐增加的特征,在板块西北边界（122°E,23°N）附近,主压应变率最大为571×10-8/a. 菲律宾海板块主应变场的空间变化与板块内部及周围的构造背景密切相关,是构造应力场的反映.     

关中盆地地壳应力场特征分析

通过收集整理关中盆地1972-2018年中小地震的震源机制解,分析其震源破裂类型与空间分布特征,反演得到关中盆地地壳应力场特征为:最大主压应力轴方位261.8°,倾角48.8°;中等主压应力轴方位74.3°,倾角40.9°;最小主压应力轴方位167.4°,倾角3.7°。同时结合活动构造,探讨关中盆地构造变形和强震发生的动力学机制。     

CHARACTERISTICS OF FOCAL MECHANISMS AND STRESS FIELD OF YUNNAN AREA

Using the seismic waveform data recorded by regional seismic network of Yunnan and Sichuan and the method of CAP, we calculate and obtain the focal mechanism of 268 earthquakes with the magnitude of M_L≥4.0 occurring in Yunnan during Jan. 1999 to Aug. 2014; then, we analyze the types and the regional feature of the focal mechanism of earthquakes in Yunnan, on the basis of the focal mechanism of 109 earthquakes analyzed by Harvard University. Based on the data of the above focal mechanism solutions, we adopt the method of damped regional-scale stress inversion to calculate the best-fitting tectonic stress tensor of every grid in Yunnan; and adopt the method of maximum principal stress to calculate the direction of maximum horizontal principal stress in Yunnan. The result shows that: (1)the strike-slip type is the most principal type of the earthquake focus in the study area and the second is the normal faulting type; while, the reverse-fault type is relatively small. The spatial distribution of focal mechanism is obvious. This reflects that the dynamic source and acting force are different in different parts of the study area. (2)The direction of the stress field in Yunnan shows a certain spatial continuity. Maximum horizontal principal compressive stress is mainly clockwise from north to south and counterclockwise from the west to the east. The direction of stress field shows inhomogeneity in space. There exist two stress conversion zones respectively in EW and NS direction. The inversion result of stress field shows that the stress field in Yunnan is complex and the principal stress direction changes greatly; and there are obvious differences in different regions.     

ESTIMATING THE MAGNITUDE OF TECTONIC STRESS BASED ON THE FRICTION CRITERIA OF FAULT AND ANALYSING THE PARAMETERS' INFLUENCE

Based on Zoback's method for estimating the tectonic stress magnitude and the two assumptions, we consider the conditions that three principal stresses are vertical principal stresses respectively(corresponding to three kinds of tectonic stress types). We deduced the formulae for estimating the tectonic stress magnitude by using the stress form factor and frictional strength of the fault and discussed the correlative influence of friction coefficient, pore pressure parameter and stress form factor on the stress value. When the maximum principal stress is approximately horizontal (when stress regime is strike-slip or reverse), the maximum principal stress (or the slope of stress increasing linearly with depth) is positively related with the friction coefficient and negatively related with the pore pressure coefficient. When the minimum principal stress is approximately horizontal (when stress regime is strike-slip or normal), the minimum principal stress (or the slope with depth) is negatively related to the friction coefficient, and positive to the pore pressure. Besides, these three parameters have great influence on the estimation of the tectonic stress magnitude. If the friction coefficient is too big and the pore pressure is too small, there could be a wide difference between the slope of the maximum principal stress increasing with depth and the slope of the minimum principal stress increasing with depth, which could lead to an unreasonable result. Our method is just an approximate estimation for the tectonic stress magnitude when crustal rocks have undergone brittle rupture or frictional sliding. The estimated results are not the tectonic stress magnitude when crust is in steady state.     

汶川MS8.0级地震断层滑动机制研究

汶川M_S8.0级地震的发震构造为龙门山断裂带,地震地表破裂主要分布在其中的北川－映秀断裂和江油－灌县断裂上,尤其是沿前者发育了长达240 km左右的地表破裂带.通过对龙门山断裂带震后断层擦痕的测量,得到311条断层擦痕数据,利用由断层滑动资料反演构造应力张量的计算方法,得到研究区8个测点的构造应力张量数据,并获得了研究区构造应力场特征：区域现代构造应力场以近水平挤压为主,最大主应力方向（σ1）为76°～121°,平均倾角9°,应力结构以逆断型为主.受构造应力场及断层几何特征的影响,地表破裂呈现出分段性：映秀—北川段主要以NW盘逆冲为主,垂直位移明显;北川以北段为逆冲兼走滑,水平位移量与垂直位移量基本相当,或水平位移略大.