我国滇西北地震活动区的活动构造与应力状态

本文根据野外调查和原地应力测量资料,讨论了滇西北地震活动区的活动构造型式和现今应力状态。资料表明,本区是由红河和中甸两条右旋走滑断裂所形成的拉分构造,其应力状态也与外区不同。地震在空间上的分布和在时间上的活动规律受这一构造型式及其应力状态的控制     

邵武——河源地震带中段地震活动趋势讨论

邵武－－河源地震带中段从1978年以来出现一次地震群体活动，属于该地震带第Ⅱ活动周期的第Ⅳ活动幕，现已转入这次活动幕的尾声，分析该区历史和现今地震活动特征及其应力状态，认为该区震源构造应力已整调、处于松驰状态。未来一段时间的地震活动将向起伏性减弱趋势发展。     

基于多参数组合分析海原—六盘山—宝鸡断裂带地震危险性

1 研究背景 近年来,易桂喜等(2006,2007)、武敏捷等(2013)利用以b值为主的地震活动性参数空间分布,结合历史及现今地震活动背景,分析活动断裂带现今活动习性,综合判断处于相对高应力和闭锁状态下活动断裂带的强震危险性.这种组合分析方法比单个活动性参数值能更好地反映断裂现今活动习性,且对地震样本需求不高,适用于地震监测能力一般、地震活动性中等地区的地震危险性判定.     

岷江上游地区第四纪构造应力状态及其与地震的关系

本文用地质、地貌、地震等综合方法研究第四纪构造应力状态。本区第四纪主压应力为北东东—南西西方向。在这种应力作用下,区内南北向断裂呈压扭方式活动,东西向断裂以张扭方式活动,北西向构造强烈隆起。现今小震活动多沿东西向断裂分布     

由地震活动参数分析安徽省新生代构造变形带现今活动习性与地震危险性

应用多个地震活动参数来判定断裂带分段落活动习性的方法,分析安徽省新生代构造变形带不同分段落的现今活动习性及地震危险性。研究结果表明：安徽省新生代构造变形带中存在着9个具有不同现今活动习性的分段落,其中,霍邱-风台、铜陵-宁国、明光-肥东3个段落现今活动习性处于较高应力背景下的相对闭锁状态．应属于有一定应变积累的潜在中强震危险段落：其它6个段落．现今活动习性处于中等或偏低应力背景下,以频繁或稀疏小震滑动为特征．未来复发中强以上地震的可能性较小。     

"霍山地震窗"小震序列运动学参数时变特征研究

利用安徽及邻近地区的数字化地震资料,详细研究了“霍山地震窗口”小震序列的构造环境背景应力和视应力变化特征。结果表明,环境应力值和视应力值不仅能反映震“源”区的应力背景强弱,在距未来强震震中比较远的特殊构造部位,即素有“地震活动穴位”的地震窗口的小地震,同样能较客观反映出孕震区附近应力环境的信息,在华东中强地震前后应力状态的差异性是显著的。     

燕山-渤海地震带的现今构造应力环境

应用中小地震的震源机制解资料,分析了燕山-渤海地震带现今构造应力场总体与分区特征.分析发现,该带现今构造应力场总体方向为:主压应力轴方位大约为70～80°,主张应力轴方位大约为340～350°;该带现今以水平、近于水平兼有一定斜向作用的主压应力为主.同时,结合有关资料分析了该带的地震活动.     

祁连山地震构造带沙层应力仪观测记录与地震活动初步分析

采用2008年在祁连山地震构造带上兰州观象台和嘉峪关中心台架设的两台沙层应力仪4年多的观测资料,分析了沙层应力记录的基本特征及其与地震活动的关系,初步探讨了沙层应力记录与强震孕育过程的关系。结果表明,沙层应力记录在一定程度上反应了地震孕育和发生过程中的一些应力变化信息,对于捕捉临震信息有一定的参考意义,但也存在较多不确定性,需要进一步分析判定。     

天山北部强震活动对区域应力扰动的分析以2012年伊犁M6.6地震和2017年精河M6.6地震为例

天山地区为典型地震活跃区, 为定量分析该构造活跃区强震对周边构造变形和地震活动的影响, 本文基于地震位错理论和岩石圈分层模型计算了天山北部近期发生的2012年伊犁和2017年精河两次M6.6地震对周围地壳形变和应力的影响。 计算结果显示伊犁地震和精河M6.6地震引起震中附近地表同震位移达数厘米, 地表同震应变量级约为10^-7; 对比天山北部地区年平均构造形变特征, M6.6强震释放了震中附近近十年的构造主压应变积累; 地震引起震中附近(80 km内)同震库仑应力变化大于1 kPa, 而距震中较远区域活动断层上库仑应力变化微弱。 结合天山北部现今地壳变形特征及区域地震分布, 初步推测两次M6.6地震的发生对震后余震有显著的触发作用, 而对区域后续微震活动的影响微弱。     

利用深井地下水位动态研究大华北地区现今构造应力场状态

在水平层状含水层(一维)模式下, 根据含水层应力与井水位变化之间的定量关系表达式, 利用华北地区40多口深井水位动态变化资料, 探索研究华北地区现今构造应力场状态。 即水位上升代表构造应力场压性增强张性减弱; 水位下降代表构造应力场压性减弱张性增强。 初步研究结果表明, 1995~1998年华北北部地区张家口-渤海构造带和山西构造带北部水位普遍上升, M_S5.0以上地震活动频繁; 1999年以后华北地区水位普遍处于下降状态, 反映了华北地区1999年以来构造应力场状态以张性为主, 整个华北地区M_S5.0以上地震活动处于相对平静状态。 该结果可为华北地区地震活动性预测研究提供应力场背景信息。     

Current tectonic deformation and seismogenic characteristics along the northeast margin of Qinghai -Xizang block

Introduction The northeast margin of Qinghai-Xizang block has become the place with close attentions from geo-specialists at home and abroad for its significant tectonic movement and intensive seismicity. Quite a number of achievements have been obtained from the studies on geological structures and strong earthquake activities (DING, LU, 1989, 1991; GUO, et al, 1992, 2000; GUO, XIANG, 1993; HOU, et al, 1999; Tapponnier, et al, 1990; Gaudemer, et al, 1995). In the Development Program…     

1996年3月19日新疆阿图什6.9级地震震源破裂特征的研究

通过对1996年3月19日新疆阿图什6．9级地震余震分布特征的研究，分析了这次地震震源破裂过程．并结合柯坪断裂带的构造运动、区域应力场的分布特征以及1972年以来该带的另外3次6级地震的余震分布方向，探讨了柯坪断裂带附近地区不同构造部位震源破裂扩展方向与强震活动的迁移方向．结果表明，本次地震震源破裂为明显的单侧破裂．柯坪断裂带的阿图什震区和柯坪震区，余震分布具有一定规律性，震源破裂基本都为单侧破裂；震源断错以逆断层为主．区内主要受NW向压应力。不同地段强震震源破裂扩展具有明显的区域特征，强余震分布方向是应力集中的体现，它标志着同一构造断裂带附近近期强震活动的迁移方向．在柯坪断裂带上这种规律更为明显。     

中国大陆东部现今构造应力状态

本文依据原地应力测量(套芯解除法90余个,水压致裂法6个),结合油田测井、震源机制解和断层现今活动资料等,综合研究了该地区的现今构造应力场特征,认为: 1.中国大陆东部地区现今构造应力状态似乎具有分区性.华北地区最大主应力方向为近东西向,太行山以西地区转为北北东向,华南地区为北西向.一个地区的主压应力方向在地下几十米至4000米大体是一致的. 2.华北地区地表以下几十米内的最大水平主压应力值一般在2——6MPa,而华南地区似乎比华北地区略高,两区的最大和最小水平主压应力平均差值也不相同。 3.现代活动的郯庐断裂带上,其剪切应力值远低于断裂带以外地区,离断裂带一定距离后,趋于区域正常值. 4.大震的发生,明显地影响极震区的应力场,但在一定时间内能恢复到原有的区域应力状态.      

FOCAL FAULTS AND STRESS FIELD CHARACTERISTICS OF M7.0 JIUZHAIGOU EARTHQUAKE SEQUENCE IN 2017

On August 8, 2017, Beijing time, an earthquake of M7.0 occurred in Jiuzhaigou County, Aba Prefecture, Sichuan Province, with the epicenter located at 33.20°N 103.82°E. The earthquake caused 25 people dead, 525 people injured, 6 people missing and 170000 people affected. Many houses were damaged to various degrees. Up to October 15, 2017, a total of 7679 aftershocks were recorded, including 2099 earthquakes of M ≥ 1.0. The M7.0 Jiuzhaigou earthquake occurred in the northeastern boundary belt of the Bayan Har block on the Qinghai-Tibet Plateau, where many active faults are developed, including the Tazhong Fault(the eastern segment of the East Kunlun Fault), the Minjiang fault zone, the Xueshan fault zone, the Huya fault zone, the Wenxian fault zone, the Guanggaishan-Daishan Fault, the Bailongjiang Fault, the Longriuba Fault and the Longmenshan Fault. As one of the important passages for the eastward extrusion movement of the Qinghai-Tibet Plateau(Tapponnier et al., 2001), the East Kunlun fault zone has a crucial influence on the tectonic activities of the northeastern boundary belt of Bayan Kala. Meanwhile, the Coulomb stress, fault strain and other research results show that the eastern boundary of the Bayan Har block still has a high risk of strong earthquakes in the future. So the study of the M7.0 Jiuzhaigou earthquake' seismogenic faults and stress fields is of great significance for scientific understanding of the seismogenic environment and geodynamics of the eastern boundary of Bayan Har block. In this paper, the epicenter of the main shock and its aftershocks were relocated by the double-difference relocation method and the spatial distribution of the aftershock sequence was obtained. Then we determined the focal mechanism solutions of 24 aftershocks(M ≥ 3.0)by using the CAP algorithm with the waveform records of China Digital Seismic Network. After that, we applied the sliding fitting algorithm to invert the stress field of the earthquake area based on the previous results of the mechanism solutions. Combining with the previous research results of seismogeology in this area, we discussed the seismogenic fault structure and dynamic characteristics of the M7.0 Jiuzhaigou earthquake. Our research results indicated that:1)The epicenters of the M7.0 Jiuzhaigou earthquake sequence distribute along NW-SE in a stripe pattern with a long axis of about 35km and a short axis of about 8km, and with high inclination and dipping to the southwest, the focal depths are mainly concentrated in the range of 2~25km, gradually deepening from northwest to southeast along the fault, but the dip angle does not change remarkably on the whole fault. 2)The focal mechanism solution of the M7.0 Jiuzhaigou earthquake is:strike 151°, dip 69° and rake 12° for nodal plane Ⅰ, and 245°, 78° and -158° for nodal plane Ⅱ, the main shock type is pure strike-slip and the centroid depth of the earthquake is about 5km. Most of the focal mechanism of the aftershock sequence is strike-slip type, which is consistent with the main shock's focal mechanism solution; 3)In the earthquake source area, the principal compressive stress and the principal tensile stress are both near horizontal, and the principal compressive stress is near east-west direction, while the principal tensile stress is near north-south direction. The Jiuzhaigou earthquake is a strike-slip event that occurs under the horizontal compressive stress.     

川滇地区7级大震前中强震震源机制变化

分析了 70年代以来 ,川滇地区发生的 8次 7级大震前 5年内 ,发生在大震孕震区和震源区内的中强震震源机制解时空分布。结果表明 ,最早中强震发生在大震震源区或其附近 ,其发震应力场与区域构造应力场一致 ,与大多数大震发震应力场一致或接近。大多数中强震震源破裂特征与大震明显不同。之后有多次中强震发生在距大震震源区较远的大震孕震区内其他地方 ,它们的发震应力场往往经历了与区域构造应力场和大震应力场一致与不一致的多次交替变化。大震前最后 1个中强震也发生在距大震震源区较近的地方 ,其发震应力场与大震发震应力场明显不一致 ,偏转了 30°～ 5 0° ,或更多 ,大多数也与区域构造应力场不一致 ,有的中强震发震断裂破裂特征与大震不一致。大震前中强震震源机制的变化 ,反映了大震孕育过程的不同阶段 ,区域构造应力场的时空调整变化和增强过程 ,以及由此引发的构造断裂异常活动 ,揭示出与大震发生有关的应力场和震源破裂特征信息     

1900年以来巴颜喀拉块体应力演化与周缘强震关系的数值模拟研究

以巴颜喀拉块体为研究对象,考虑区域地质构造差异,主要活动断裂带,活动块体和边界断裂带的划分结果,引入深部三维速度结构,建立能反映地表起伏和岩石圈分层结构的青藏高原地区三维黏弹性有限元模型.以地壳水平运动速率观测值和最大主压应力方向测量值为约束条件重建研究区现今构造背景应力场.在此基础上模拟了自1900年以来巴颜喀拉块体周缘的7级以上强震序列,从库仑破裂应力角度研究了应力演化与强震的关系、强震之间的相互作用关系以及长期构造加载对强震的影响.研究结果表明,巴颜喀拉块体周缘强震的发生可能与震源区总应力的增加有关.2008年汶川地震导致龙门山断裂带南段应力增加,表明汶川地震对2013年芦山地震有促进作用.鲜水河断裂带上的7级以上强震序列对发生在邻近龙门山断裂带上的2008年汶川地震和2013年芦山地震有延迟作用.     

FOCAL MECHANISM SOLUTION AND TECTONIC STRESS FIELD CHARACTERISTICS OF THE MIDDLE TIANSHAN MOUNTAINS,XINJIANG

The middle part of the Tianshan Mountains in Xinjiang is located in the north-central part of the Tianshan orogenic belt, between the rigid Tarim Basin and Junggar Basin. It is one of the regions with frequent deformation and strong earthquake activities. In this paper, 492 M_S>2.5 earthquake events recorded by Xinjiang seismograph network from 2009 to 2018 were collected. The M_S3.5 earthquake was taken as the boundary, the focal mechanism solutions of the earthquake events in this region were calculated by CAP method and FOCEMEC method respectively. At the same time the focal mechanism solutions of GCMT recorded historical earthquake events in this region were also collected. According to the global stress map classification standard, the moderate-strong earthquakes in the region are mainly dominated by thrust with a certain slip component, which are distributed near the combined belts of the Tarim Basin, Junggar Basin, Turpan Basin and Yili Basin with Tianshan Mountains. The thrust component decreases from south to north, while the strike-slip component increases. The spatial distribution characteristics of the tectonic stress field in the middle section of the Tianshan Mountains in Xinjiang are obtained by using the damped regional-scale stress field inversion method. The maximum principal compressive stress in axis the study area rotated in a fan shape from west to east, the NW direction in the western section gradually shifted to NE direction, its elevation angle is nearly horizontal, in the state of near horizontal compression. The minimum principal compressive stress axis is nearly EW, and the elevation angle is nearly vertical. Influenced by large fault zones such as Kashi River, Bolhinur, Nalati, Fukang, the southern margin of the Junggar and the north Beiluntai, the local regional stress field presents complex diversity. Under the influence of the northward extrusion of Pamir and Tarim blocks, the whole Tianshan is shortened by compression, but its shortening rate decreases from south to north and from west to east, the stress shape factor increases gradually from west to east, the intermediate principal compressive stress axis exhibits a change in compression to extension. There are some differences in the characteristics of tectonic stress field between the north and south of Tianshan Mountains. The regional maximum principal compressive stress axis is 15° north by east on the south side, while it is nearly NS on the north side. The deformation of the Tianshan Mountains and the two basins on both sides is obviously larger than that in the inside of the mountain. Changes in the crustal shortening rate caused by the rotation of the rigid Tarim block and Junggar block to the relatively soft Tianshan block, as well as the uplifts of Borokonu and Bogda Mountains, the comprehensive influence of the material westward expansion constitute the stress field distribution characteristics of the north and south sides of the middle section of Tianshan Mountains. The recent two M_S6.6 earthquakes in the region caused the regional stress field to rotate counterclockwise. The post-earthquake stress field and the main source focal mechanism solution tend to be consistent. The seismic activity in the study area is week in the south and strong in the north. The focal depth is about 20km. Most strike-slip earthquakes occur near the junction belt of the Tianshan and Junggar Basin.     

澜沧,耿马震区断层启动系数与大震序列发震断裂研究

在分析构造应力场最大主应力方向和断层走向之间的夹角与断层错动关系的基础上，同时还考虑断层的几何特征，错动性质以及应力场状态等因素，提出以断怪启动系数Ｋ值来定量表征处在相同构造尖力环境中，不同走向的活动断裂的活动程度，并以１９８８年澜沧－耿马大震序鲁为例，计算了大震和强余震震源机制节面的断层启动系数，对震区主要活动断裂在近似情况下也计算了断层启动系数，以此在结合地震破裂带等资料对大震和强余震的发震断     

2018年5月松原MS5.7地震序列发震断层及应力场特征

利用双差定位方法对2018年松原M_S5.7地震序列中M_L≥1.0地震重新定位,之后使用CAP方法求解松原M_S5.7地震序列中强地震的震源机制解,再借助MSATSI软件包反演得到松原地区的区域应力场。综合分析以上研究结果得到如下结论:① 松原M_S5.7地震序列发生在NW走向的第二松花江断裂与NE走向的扶余—肇东断裂交会处,将地震精定位结果沿两条断层走向作剖面分析,NW向剖面主轴长度约为5 km,震中分布均匀,NE向剖面主轴长度亦约为5 km,震中呈倾向NE的高倾角分布;② 该序列中的4次M_L≥3.7地震的震源机制解具有良好的一致性:节面Ⅰ走向为NE向,节面Ⅱ走向为NW向,均为高倾角走滑断层。中强地震的震源机制节面解与第二松花江断裂性质基本一致,由此推断第二松花江断裂是本次松原地震的发震断层;③ 松原地区的主压应力方位角为N86°E,倾角为7°,主张应力方位角为N24°E,倾角为71°。松原地区的区域应力场既受到大尺度的板块构造运动的控制,又受到区域构造运动的影响。在太平洋板块对北东亚板块向西俯冲作用下,东北地区产生了近EW向的主压应力,受周边地质构造控制,松辽盆地内NE向断裂与NW向断裂交会处易发生走滑型地震,2018年松原M_S5.7地震正是在这种构造作用控制下发生的中强地震。      

汶川MS8.0地震前后龙门山及其 邻区构造应力场时空分布特征

基于2000年7月—2009年6 月龙门山及其邻区的震源机制解资料, 采用Gephart & Forsyth方法, 反演得到了汶川地震前后该地区构造应力主方向的空间分布. 结果显示: 沿鲜水河断裂带及其北部地区, 构造应力场变化显著, 区域构造应力的最大主应力方位由NNW变为NW, 断层错动类型由正断型兼走滑型变为走滑型; 沿龙门山断裂带的构造应力最大主应力方向仍然为近EW和NE向, 但其EW向范围在向NE方向扩张, 其南部汶川地震震中附近异常带范围在收缩. 另一方面, 对上述时间段龙门山及其邻区不同时段构造应力场的反演结果表明, 其构造应力场的特征参数(包括R值、 应力洛德参数μ′以及3个主应力的方位角和仰角等)均从第13时窗开始出现显著变化, 这表明第13时窗(2006年12月—2007年1月)是一个构造应力显著变化的特征窗口. 在该时窗内, 地震能量积累达到一个临界状态, 是汶川M_S8.0地震发生的时间节点.