新疆塔城盆地断裂的晚第四纪活动特征

塔城盆地在大地构造上,位于哈萨克斯坦—准噶尔板块内,是西准噶尔山地的一山间盆地。在盆地周边及邻近地区主要分布有塔克台断裂、冬格列克断裂、裕民南断裂、巴尔鲁克山东缘断裂等。这些断裂在晚第四纪以来发生过显著的活动,断错了山前洪积扇和河流阶地及河漫滩,并形成连续分布的地表错动形变带。形变带主要由断层陡坎、断塞塘、挤压鼓包、沟槽等组成。经调查研究,形变带为古地震形变带。通过野外实地调查和大型探槽开挖及光释光年代测定,断裂在晚更新世或全新世时期发生过新活动及古地震。     

西准噶尔冬别列克断裂晚第四纪以来的阶地位错与滑动速率

冬别列克断裂是一条全新世活动断裂,位于西准噶尔造山带的关键位置,该断裂总长120km,走向NE。晚第四纪以来,冬别列克断裂的持续活动使得断裂沿线各级地貌面发生了明显的左旋位错,在塔城盆地东侧形成线性连续且笔直的陡坎地貌。文中利用高精度无人机和差分GPS对阿合别斗河多级阶地的左旋位错量进行了面状航拍、测量,建立了分辨率高达0. 1m的数字地形数据,发现T5—T2阶地陡坎的最大左旋位错量依次为30. 7m、12. 0m和8. 7m。通过光释光测年方法得到了各级阶地(T5—T1)的年龄,进而得出冬别列克断裂晚更新世以来的左旋滑动速率为0. 7～0. 94mm/a,结合阶地侧向侵蚀特征,分析认为T4、T2阶地的滑动速率更加接近真实值(0. 91±0. 18) mm/a。结合西准噶尔的其它2条大型走滑断裂(达尔布特断裂和托里断裂)的滑动速率,并对比西准噶尔地区的GPS速率,认为该地区NE向的走滑运动以冬别列克断裂为主,吸收大量剩余变形,同时保持相对较高的左旋滑动速率。     

孟连断裂晚第四纪活动特征

孟连断裂是滇西南地区的1条区域性活动断裂。本文通过地形地貌、断裂剖面及地震活动等对断裂的空间展布及晚第四纪活动性进行分析和研究,获得了断裂活动时代和活动速率等参数。研究表明:孟连断裂晚第四纪期间仍在活动,最新活动时代为全新世,运动性质以左旋走滑为主,晚第四纪以来的平均水平滑动速率为3.8—5.1mm/a;该断裂控制着孟连、勐阿等第四纪盆地的发展及演化,沿断层发生了1995年7月12日中缅边境7.3级地震。     

滇西南打洛断裂晚第四纪活动特征

滇西南打洛断裂位于青藏高原向SE方向物质挤出的最前端,其构造活动记录了青藏高原东南缘最新构造活动信息。通过卫星影像分析、现场追踪调查、探槽开挖、年代样品测试、断错微地貌高精度测绘等工作,对打洛断裂晚第四纪活动特征进行深入研究。结果表明,打洛断裂是一条全新世活动的左旋走滑断裂,晚第四纪水平滑动速率上限值为(2.5±0.1)mm/a,下限值为(0.8±0.1)mm/a,平均约(1.7±0.9)mm/a。假定断裂滑动速率基本保持恒定,根据沿断裂地质体最大位错约(11.2±0.5)km,估算其走滑活动构造转换时代应为(4.4~14.9)Ma B.P.。断裂最近一次构造活动时间为(360±30)a^850±30a B.P.。     

谷露盆地西缘断裂晚第四纪活动初步研究

该文通过遥感解译及实际地质调查,将谷露盆地西缘断裂自南向北分为6段: 年波—顶莫多段、 顶莫多—巴仁多段、 巴仁多—得木来段、 得木来东侧—过龙孔玛段、 过龙孔玛—烟它段、 烟它—凶欧错北段。从地质和地貌现象上证明,谷露盆地西缘断裂既有正断的垂直运动,也有右旋的水平运动。由位错量显示,无论是垂直运动还是水平运动,都是多次活动的结果。     

大柴旦断裂中段晚第四纪活动特征

通过航卫片遥感数据解译、野外地质地貌调查,并结合差分GPS等测量手段,获取大柴旦断裂晚第四纪以来的地质地貌特征。结果显示：大柴旦断裂总长约135 km,整体上显示为一反“S”形,根据断裂走向的变化、地貌特征、活动强弱等,大致以温泉沟、塔塔棱河为分界点,可将大柴旦断裂分为三段。晚第四纪以来,该断裂北段和南段逆冲性质较为明显。本次工作集中在断裂中段,该段以右旋逆冲活动为主,逆冲量和右旋量在不同地貌面上是不同的,显示出明显的多期次活动特征。野外天然古地震剖面揭示出1次古地震事件,发生在(2 402.5±57.5) a.B.P之后,表明该断裂在全新世活动强烈,与该区域近年来频繁的强震活动相吻合。     

阿尔金南缘断裂东段晚第四纪活动特征

阿尔金断裂的几何学和运动学特征对研究青藏高原构造演化和陆内地震机理非常重要。为定量科学研究较为薄弱的阿尔金南缘断裂东段的运动学参数,我们采用航卫片的解译、野外调查、地形测绘和年代学样品测试等多种方法对该段进行了初步研究。结果显示该段断裂主要以左旋走滑运动为主,且沿线存在较多的小位移,其位移空间分布的3个明显峰值分别为4.5m、8m和13m。根据河流阶地的左旋位移和相应的地貌面沉积年龄,得到晚第四纪以来阿尔金断裂东段的走滑速率约为2.7±0.9mm/a。基于所获得的定量参数,认为该段断裂向东以应变分解的形式将其应变量传递到相邻的逆冲断裂上。     

罗布泊捷山子断裂晚第四纪活动特征

位于罗布泊的捷山子断裂,在航、卫片上线性影像清晰,平面上由2-3条断层组成。罗布泊东台地以东,断裂在地貌上构成较宽阔的断裂谷地或断陷盆地的边界,同时也构成了元古界、花岗岩体与古近系、新近系以及第四系的分界。在罗布泊东台地断裂切割由中更新世—晚更新世湖积物构成的东台地（雅丹地貌）。在赛里克沙依断陷盆地,断裂断错了晚更新世晚期洪积扇及冲沟Ⅰ、Ⅱ级阶地,并形成长约40 km的断层陡坎。捷山子断裂的中、西段在晚更新世有过显著的活动。     

天山南部北轮台断裂带东段晚第四纪活动特征

利用卫星影像资料解译,通过野外实地考察并结合气象、地貌、时间的分析,对长逾300 km的北轮台断裂带的晚第四纪活动速率进行定量研究。北轮台断裂带西部为库车坳陷的北部控制性断裂带,东部为发育于山前冲洪积扇面上的断层陡坎,在阿克艾肯段断裂形成了高达38 m的断层陡坎,为多次7~7.5级地震活动的产物,其逆冲抬升速率可达到1.52 mm/a;而在吉格代布拉克段发育有高10~20 m的断层陡坎,此段断裂带的活动速率为0.1~0.9 mm/a。北轮台断裂东段自晚更新世以来活动明显,切割多级阶地面,形成不同高度的古地震形变带,估算最近一次古地震的离逝时间为1.7 ka。     

托斯台逆断裂-褶皱带晚第四纪活动特征

托斯台逆断裂-褶皱带位于乌鲁木齐山前坳陷的西部,为近东西向展布的新生代逆断裂．背斜带。它主要由北单斜带、中部背斜带和南单斜带3个构造带组成,在各构造带均发育逆活动断裂。地震勘探资料显示,南单斜带与中部背斜带为滑脱体,逆断裂在深部沿滑脱面与清水河子深断裂相汇。研究表明,北单斜带与中部背斜带逆断裂断错了晚更新世堆积物,在晚更新世有显著的活动;南单斜带逆断裂断错了全新世堆积物,在全新世时期有最新活动。中部背斜带逆断裂晚更新世以来水平缩短速率为0．6～1．3mm／a;南单斜逆断裂全新世水平缩短速率为0．2～0．6mm／a。     

GEOLOGICAL EVIDENCES OF LATE QUATERNARY ACTIVITY OF MOTUO FAULT IN EASTERN HIMALAYAN SYNTAXIS

Motuo Fault locates at the east of Namjagbarwa Peak in eastern Himalayan syntaxis.Based on the remote sensing interpretation,the previous work,and with the field investigation,this paper obtains the spatial distribution and movement characteristics of Motuo Fault in China,and geological evidences of late Quaternary activity.Two trenches in Motuo village and Dongdi village located in Yalung Zangbo Grand Canyon reveal that the Motuo Fault dislocates the late Quternary stratum and behaves as a reverse fault in Motuo village and normal fault in Dongdi village.Motuo Fault is dominated by left-lateral strike-slip associated with the faulted landforms,with different characteristics of the tilting movement in different segments.The trench at Didong village reveals the latest stratum dislocated is~2780±30 a BP according to radiocarbon dating,implying that Motuo Fault has ruptured the ground surface since late Holocene.The movement of left-lateral strike-slip of Motuo Fault is related to the northward movement process of Indian pate.     

TERRACE DEFORMATION AND SLIP RATES OF THE DONGBIELIEKE FAULT IN WESTERN JUNGGAR BASIN SINCE THE LATE QUATERNARY

Strike-slip fault plays an important role in the process of tectonic deformation since Cenozoic in Asia. The role of strike-slip fault in the process of mountain building and continental deformation has always been an important issue of universal concern to the earth science community. Junggar Basin is located in the hinterland of Central Asia, bordering on the north the Altay region and the Baikal rift system, which are prone to devastating earthquakes, the Tianshan orogenic belt and the Tibet Plateau on the south, and the rigid blocks, such as Erdos, the South China, the North China Plain and Amur, on the east. Affected by the effect of the Indian-Eurasian collision on the south of the basin and at the same time, driven by the southward push of the Mongolian-Siberian plate, the active structures in the periphery of the basin show a relatively strong activity. The main deformation patterns are represented by the large-scale NNW-trending right-lateral strike-slip faults dominated by right-lateral shearing, the NNE-trending left-lateral strike-slip faults dominated by left-lateral shearing, and the thrust-nappe structure systems distributed in piedmont of Tianshan in the south of the basin. There are three near-parallel-distributed left-lateral strike-slip faults in the west edge of the basin, from the east to the west, they are:the Daerbute Fault, the Toli Fault and the Dongbielieke Fault. This paper focuses on the Dongbielieke Fault in the western Junggar region. The Dongbielieke Fault is a Holocene active fault, located at the key position of the western Junggar orogenic belt. The total length of the fault is 120km, striking NE. Since the late Quaternary, the continuous activity of the Dongbielieke Fault has caused obvious left-lateral displacement at all geomorphologic units along the fault, and a linear continuous straight steep scarp was formed on the eastern side of the Tacheng Basin. According to the strike and the movement of fault, the fault can be divided into three segments, namely, the north, middle and south segment. In order to obtain a more accurate magnitude of the left-lateral strike-slip displacement and the accumulative left-lateral strike-slip displacement of different geomorphic surfaces, we chose the Ahebiedou River in the southern segment and used the UAV to take three-dimensional photographs to obtain the digital elevation model(the accuracy is 10cm). And on this basis, the amount of left-lateral strike-slip displacement of various geological masses and geomorphic surfaces(lines)since their formation is obtained. The maximum left-lateral displacement of the terrace T₅ is(30.7±2.1)m and the minimum left-lateral displacement is(20.1±1.3)m; the left-lateral displacement of the terrace T₄ is(12±0.9)m, and the left-lateral displacement of the terrace T₂ is(8.7±0.6)m. OSL dating samples from the surface of different level terraces(T₅, T₄, T₂ and T₁)are collected, processed and measured, and the ages of the terraces of various levels are obtained. By measuring the amount of left-lateral displacements since the Late Quaternary of the Dongbielieke Fault and combining the dating results of the various geomorphic surfaces, the displacements and slip rates of the fault on each level of the terraces since the formation of the T₅ terrace are calculated. Using the maximum displacement of(30.7±2.1)m of the T₅ terrace and the age of the geomorphic surface on the west bank of the river, we obtained the slip rate of(0.7±0.11)mm/a; similarly, using the minimum displacement of(20.1±1.3)m and the age of the geomorphic surface of the east bank, we obtained the slip rate of(0.46±0.07)mm/a. T₅ terrace is developed on both banks of the river and on both walls of the fault. After the terraces are offset by faulting, the terraces on foot wall in the left bank of the river are far away from the river, and the erosion basically stops. After that, the river mainly cuts the terraces on the east bank. Therefore, the west bank retains a more accurate displacement of the geomorphic surface(Gold et al., 2009), so the left-lateral slip rate of the T₅ terrace is taken as(0.7±0.11)mm/a. The left-lateral slip rate calculated for T₄ and T₂ terraces is similar, with an average value of(0.91±0.18)mm/a. In the evolution process of river terraces, the lateral erosion of high-level terrace is much larger than that of low-level terrace, so the slip rate of T₄ and T₂ terraces is closer to the true value. The left-lateral slip rate of the Dongbielieke Fault since the late Quaternary is(0.91±0.18)m/a. Compared with the GPS slip rate in the western Junggar area, it is considered that the NE-trending strike-slip motion in this area is dominated by the Dongbielieke Fault, which absorbs a large amount of residual deformation while maintaining a relatively high left-lateral slip rate.     

新疆伊宁盆地活动断裂新活动特征研究

新疆伊宁盆地主要分布有巩留南、喀什河、雅马特等6条活动断裂，断裂走向近东西向与北酉一北北西向。其中巩留南断裂、喀什河断裂、雅马特断裂等在晚更新世一全新世时期有过多次显著的新活动，切错了晚更新世一全新世堆积物。在喀什河断裂上1812年发生了8级大展，形成长约100km的地震形变带。在巩留南断裂、雅马特断裂、伊宁断裂上也有受控于断裂近代新活动的中等地震发生。     

THE TECTONIC ACTIVITY CHARACTERISTICS OF AWANCANG FAULT IN THE LATE QUATERNARY,THE SUB-STRAND OF THE EASTERN KUNLUN FAULT

It is well known that the slip rate of Kunlun Fault descends at the east segment, but little known about the Awancang Fault and its role in strain partitioning with Kunlun Fault. Whether the sub-strand(Awancang Fault) can rupture simultaneously with Kunlun Fault remains unknown. Based on field investigations, aerial-photo morphological analysis, topographic surveys and ¹⁴C dating of alluvial surfaces, we used displaced terrace risers to estimate geological slip rates along the Awancang Fault, which lies on the western margin of the Ruoergai Basin and the eastern edge of the Tibetan plateau, the results indicate that the slip rate is 3mm/a in the middle Holocene, similar to the reduced value of the Kunlun Fault. The fault consists of two segments with strike N50° W, located at distance about 16km, and converged to single stand to the SE direction. Our results demonstrate that the Awancang fault zone is predominantly left-lateral with a small amount of northeast-verging thrust component. The slip rates decrease sharply about 4mm/a from west to east between the intersection zone of the Awancang Fault and Kunlun Fault. Together with our previous trenching results on the Kunlun Fault, the comparison with slip rates at the Kunlun fault zone suggests that the Awancang fault zone has an important role in strain partitioning for east extension of Kunlun Fault in eastern Tibet. At the same time, the 15km long surface rupture zone of the southeast segment was found at the Awancang Fault. By dating the latest faulted geomorphologic surface, the last event may be since the 1766±54 Cal a BP. Through analysis of the trench, there are four paleoearthquake events identified recurring in situ on the Awancang Fault and the latest event is since (850±30)a BP. The slip rate of the Awancang Fault is almost equivalent to the descending value of the eastern part of the east Kunlun Fault, which can well explain the slip rate decreasing of the eastern part of the east Kunlun Fault(the Maqin-Maqu segment)and the characteristics of the structure dynamics of the eastern edge of the Tibet Plateau. The falling slip rate gradient of the eastern Kunlun Fault corresponds to the geometric characteristic. It is the Awancang Fault, the strand of the East Kunlun Fault that accommodates the strain distribution of the eastward extension of the east Kunlun Fault. This study is helpful to seismic hazard assessment and understanding the deformation mechanism in eastern Tibet.     

天津海河隐伏断裂的晚第四纪活动特征研究

在海河隐伏断裂精确定位的基础上 ,文中利用天津地区晚第四纪地层中的 4个海相地层作为标志层 ,通过地质钻孔勘探、微体古生物鉴定、地层对比及年代学测定和研究 ,获得了海河断裂的晚第四纪活动特征。研究表明 ,海河断裂在天津市区段的上断点埋深为 2 1m ,对应的最新活动时代为晚更新世晚期至全新世早、中期 ,塘沽区段的上断点埋深为 16 4m ,最新活动时代已进入了全新世早、中期 ;天津市区段在晚更新世晚期 (36 2 90aBP)以来 ,垂直运动速度为 0 2 4 8mm/a ,塘沽区段全新世(72 0 0aBP)以来的平均垂直运动速率为 0 333mm/a。这表明海河断裂塘沽区段 (东段 )的活动性明显高于市区段 (西段     

骊山山前断裂第四纪活动性的研究

骊山山前断裂是发育于骊山凸起北侧的一条近东西走向并向北倾斜的正断层。断裂形变遗迹,地貌标志、新生代沉积物的厚度变化特征表明,该断裂第四纪晚期以来,在区域构造引张应力场的控制下,一直作掀斜式的倾向拉张运动。在长期的形变过程中表现了蠕滑和粘滑两种活动方式。现在仍在以蠕动的方式运动着。     

青藏高原东缘岷山活动地块周缘的地震活动特征与启示

深入理解活动地块如何控制区域强震活动是地震危险性评价的关键。文中采用双差定位法对岷山活动地块及其邻近地区2000—2019年39 076个小地震进行重新定位,并结合1972—1999年同区域仪器记录的地震目录,共计获得该区48 110个地震的位置。在此基础上,对研究区内自1933年以来的4个M≥7.0大地震不同时段的地震序列空间分布特征进行了精细分析。结果表明:这4次M≥7.0的地震序列在空间上均沿着岷山活动地块边界带分布,显示活动地块对区域大地震的孕育和发生具有明显的控制作用。同时,区域地震重定位结果和不同时段地震序列的空间分布较好地限定了4次大地震的发震断裂及其位置。综合分析结果认为,1976年松潘M_S7.2地震与2017年九寨沟M_S7.0地震的发震断层走向基本相同,但它们与1976年平武M_S7.2地震的发震断层在走向上存在约60°的差异。这3次大地震的发震断层可能分属于2条断裂。其中,2017年九寨沟M_S7.0地震和1976年松潘M7.2地震的发震断层为NW向的树正断裂,而1976年平武M