This work presents a study of late Quaternary activity on the Jinta Nanshan Fault (JTF), to constrain its properties including seismic hazard, and to understand the tectonic evolution of the northern edge of the Tibetan Plateau. The JTF has developed during northeastward growth of the Qilian fold-and-thrust belt and eastward growth of the Altyn Tagh Fault. Based on remotely-sensed image interpretation and field investigation, trench studies, high-resolution terrain construction and Optical Stimulated Luminescence dating, we study the fault geometry and slip motion, and constrain the slip rate and the latest earthquake for the JTF. The JTF continues as far southeast as the Heihe River and shows predominantly left-lateral strike-slip displacement. The left-lateral slip rate is 0.27-0.48 mm/yr since late Pleistocene, much larger than the vertical slip rate of 0.05 +/- 0.01 mm/yr. The latest rupture event of the JTF is slightly before 1 ka, which could be related to the poorly-recorded 756 CE earthquake in Hexi Corridor, and is also associated with fresh offset during this earthquake in the geomorphology of the east segment of the JTF. Strike-slip offset in this earthquake is estimated as 3.2 +/- 0.4 m, with a rupture length of at least similar to 13 km, indicating a moment magnitude of 6.4-7.2. We estimate the recurrence interval as 8-13 ka, based on the size of the latest offset and the slip rate of 0.27-0.48 mm/yr. These results indicate that the strike-slip continuation of the Altyn Tagh Fault dominates the slip behaviour of the JTF. The small strike-slip rate, and the match between the strike-slip of the JTF and the vertical slip of the North-South Normal Faults (NSF) at its eastern end, permit the interpretation that the slip of Altyn Tagh Fault is completely accommodated by crustal extension at the NSF, and dies out at the eastern end of the Jinta Nanshan region.

The epicenter of the 2017 Qinghai Zeku MS4.9 earthquake was located near the SN-striking Riyueshan fault, while the focal mechanism solutions and the dominant arrangement of seismic sequence are inconsistent with the Riyueshan fault. In this paper, we have discovered EW- and NW-trending faults near the epicenter, by methods of remote sensing interpretation and field investigation. These faults are western terminal structures of Xiahe fault, in which the EW-trending faults are north-dipping and associated with kinematics including both left-lateral and vertical slip. Meanwhile, we use double differential positioning to relocate seismic sequences of Zeku MS4.9 earthquake. Results show that seismic arrangements consist of two segments striking NW and EW. The seismic profile crossing EW-striking segment indicates a north-dipping fault plane. Well consistence is found between Xiahe fault and seismic arrangements of Zeku MS4.9 earthquake, which leads us to the speculation that the seismogenic fault of Zeku earthquake is Xiahe fault. From a regional perspective, the Xiahe fault might be one strand of dissipating faults in the western end of the West Qinling fault, and the Zeku MS4.9 earthquake represents tectonic activity of the western end of the West Qinling fault. Besides，the northwestward turn of fault striking and reverse slipping of Xiahe fault might also be attributed to the right-lateral shearing effects of Riyueshan fault. Results of this paper highlight the significance of improving active fault traces, especially for the secondary or pre-existing faults in a tectonic active area.

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.

昌马盆地为祁连山西端的山间盆地,前人一直关注其周边断裂(如昌马断裂)的构造变形,盆地内部变形则鲜有研究.基于遥感解译和野外考察、探槽开挖、差分GPS和放射性碳(14C)测年等方法,发现昌马盆地西北部的一条活动断层.断层长约4 km,总体走向NEE,倾向SE,倾角陡立,断层地貌表现为陡坎、复陡坎、断层沟槽等,陡坎高度0～5.6 m,由WS向NE逐渐增大.断层运动性质以正断为主,最新活动时代为全新世,并识别出2期古地震事件:6 670～6 885 a B.P.和26 330～26 915 a B.P..研究结果表明,在青藏高原东北缘向NE方向挤压扩展的背景下,祁连山造山带发生NW-SE向伸展,导致其西端受到SE向拉张作用而形成正断层.

西秦岭造山带位于东昆仑断裂和西秦岭北缘断裂的应变转换区,关于该区宏观地形地貌与构造活动的关系研究仍较薄弱.文章基于分辨率为30 m的SRTM1-DEM数据,利用ArcGIS 10.2软件的空间分析工具集(地表分析、水文分析等),提取西秦岭地区的地形地貌参数(坡度、起伏度)、流域地貌参数(流域盆地不对称度)和3条地形条带剖面,据此分析西秦岭地区的宏观地形地貌特征,结合区域活动断裂的几何图像和走滑分解,探讨西秦岭地区宏观地形地貌与构造活动的关系.研究结果如下:第一,西秦岭南部为坡度和起伏度的高值区,呈帚状散开形态,以3像素×3像素为统计单元的坡度可达86°,起伏度可达694m;当步长为0.54 km时,西秦岭南部白龙江流域的平均地形起伏度(862m、1104m、1200m)显著高于西秦岭北部的洮河-渭河流域(489 m、594m、526m),白龙江流域的河谷横剖面呈窄"V"形,以上结果表明西秦岭南部为地形异常隆起区,受到了强烈的构造抬升与河流下切;第二,白龙江流域盆地不对称度为67.5,远离对称状态(流域盆地不对称度=50),白龙江南西侧的流域面积远大于北东侧,说明白龙江流域南西侧受到了更强的构造抬升,发生由南西向北东的构造掀斜;洮河流域盆地不对称度为48.7,接近对称状态(流域盆地不对称度=50),洮河上游南、北两侧的流域面积相当,未受到明显的差异抬升,洮河下游西侧的流域面积明显大于东侧,说明西侧受到了更强的构造抬升,发生由西向东的构造掀斜;第三,西秦岭南部的地形异常隆起区与活动断裂图像均呈帚状散开形态,空间分布近重合,说明西秦岭南部的地形隆起与构造活动关系密切,由于活动断裂(塔藏断裂、白龙江断裂和光盖山-迭山断裂)的走向顺时针旋转,部分走滑分量转换为北东向的挤压缩短和垂向抬升分量,促使西秦岭南部发生异常强烈的地形隆起和构造抬升,形成地形异常隆起区;塔藏断裂更大的走向旋转角(30°)和走滑速率,使更多的走滑分量转换为挤压缩短和垂向抬升分量,导致白龙江流域南西侧受到更强烈的构造抬升,形成西秦岭南部由南西向北东的构造掀斜.宏观地形地貌和区域构造特征支持塔藏断裂、白龙江断裂和光盖山-迭山断裂均是东昆仑断裂东段的组成部分,分配了东昆仑断裂东段的左旋走滑分量,东昆仑断裂东端表现为帚状散开的断裂系统,具有大型走滑断裂端部的典型构造形态,并控制了帚状的地形异常隆起区.

在阿拉善地块西部新发现一条活动断裂——鼎新断裂,该断裂位于金塔县鼎新镇以东,长约30 km,走向100°～130°,几何形态略向NE凸出.通过差分GPS实测鼎新断裂的15条断层陡坎,发现陡坎高度为(0.4±0.1)～(23.8±1.0)m,陡坎高度中间大、向东西两侧减小,说明断裂具有长期的倾滑活动.在断裂东端开挖2个探槽,探槽显示陡倾的逆断层,光释光测年结果显示被断错的最新地层的沉积年龄分别为(23.38±1.99)ka和(31.25±2.66)ka,说明断裂的最新活动时代至少为晚更新世晚期.鼎新断裂、俄博庙断裂等一系列活动断裂的发现,提高了区域大震危险性,两条断裂截然不同的几何学和运动学特征体现了阿拉善内部构造变形的复杂性,其动力学特征需要进一步深入研究.

北京时间2022年1月8日,青海省门源县发生了MS6.9地震,震中位于冷龙岭断裂西端与托莱山断裂过渡区.地震发生后,文章利用亚米级分辨率的高分7号卫星影像对本次地震产生的地震破裂带进行详细解译,并与野外调查结果进行对比,获得此次地震地表破裂带分布及组合特征.结果显示,此次地震形成两条破裂带,长度分别约21 km和5 km,分别沿冷龙岭断裂西段和托莱山断裂东段展布.地震破裂带由一系列雁列式地震裂缝、挤压鼓包及拉张凹陷组成,破裂带组合特征反映出发震断裂明显的左旋走滑特征,但利用影像并未识别出同震位错等定量数据.在此基础上,文章对比冷龙岭断裂东段存在的历史地震破裂带,讨论了冷龙岭断裂未来地震危险性问题.

酒西盆地位于祁连山北缘、河西走廊西端,是一个被活动断裂围限的新生代压陷性盆地,盆地周缘及内部发育多条活动断裂.通过对前人古地震资料的总结分析和野外补充调查,发现酒西盆地断裂古地震大多符合特征地震模式,复发周期约为3～5 ka,根据经验公式推断,每次地震的震级约为6.8～7.2级.从区域古地震角度看,酒西盆地地震的发生具有丛集的特征.全新世以来存在3个丛集期,分别为10～8 ka、5.5～3.5 ka、2 ka以来,每个丛集期的长度约为2 ka.从复发特征和离逝时间上看,盆地内部的阴洼山断裂和白杨河断裂接近复发周期,具有较高的地震危险性.

嘉峪关断裂位于河西走廊西端,是酒西盆地和酒东盆地的分界断裂,其最新活动特征及强震危险性关系到嘉峪关地区及相关文物古迹的地震灾害问题.基于高分辨率卫星影像解译及野外考察,发现嘉峪关断裂中段由多条分支断裂组成,通过古地震探槽研究以及光释光方法测年,对断裂古地震特征进行了研究.结果表明,嘉峪关断裂最新的一次地震事件发生在约4.3～5.3 ka,之前在约20.0～21.2 ka、37.0～45.0 ka、58.1 ka分别发生过3次古地震事件.根据经验公式,嘉峪关断裂具有发生Mw7.0左右强震的潜能及危险性.在此震级下,嘉峪关城楼文物区的烈度可达到Ⅸ度,嘉峪关市区烈度会达到Ⅷ度.因此,嘉峪关断裂是本区防震减灾需重点关注的发震断层.

通常认为甘肃北山是构造稳定区,不发育活动断裂,近年来新发现的俄博庙活动断裂挑战了这一传统认识,深入研究该断裂的新活动特征和活动速率,对于重新认识北山地区的新构造活动以及青藏高原和阿拉善块体的相互作用等问题具有重要意义.文中基于卫星影像解译、探槽开挖、差分GPS和无人机摄影测量、光释光测年等成熟的活动构造研究方法,定量研究了俄博庙断裂的新活动特征,得到以下认识:首先,文中完善了俄博庙断裂的几何展布,将断裂长度由约20km延长至45km,根据破裂长度与震级的经验关系推断俄博庙断裂具有发生7级地震的能力;其次,查明了断层陡坎的形态和成因,发现正向陡坎和反向陡坎交替发育,反向陡坎的高度为(0.22±0.02)～(1.32±0.1)m,正向陡坎的高度为(0.33±0.1)～(0.64±0.1)m,反向陡坎受由南向北低角度逆冲的断层控制,断层倾角为23°～86°,正向陡坎受倾向S的高角度正断层控制,断层倾角为60°～81°;另外,断层的左旋走滑比倾滑更显著,西段19条冲沟的左旋位移为(3.8±0.5)～(105±25)m,根据其中最典型的一条冲沟的阶地陡坎的左旋位移量(16.7±0.5)m和上阶地年龄(11.2±1.5)ka,得到俄博庙断裂晚更新世末以来的左旋滑动速率为(1.52±0.25)mm/a.晚新生代以来,在青藏高原NE向扩展的构造背景下,俄博庙断裂的新活动特征可能响应了青藏高原与阿拉善块体之间的相对剪切分量.

临泽断裂在地貌上可见3条断层陡坎,总体走向NNW,最长约8 km,东侧和中间陡坎主体倾向E,西侧陡坎倾向W.①利用差分GPS对3条断层陡坎进行了详细的测量,发现临泽断层陡坎较低,局部发育多级断层陡坎,坡角较缓,高度几十厘米至1米多;②在临泽断裂上选取4个探槽剖面进行古地震分析、样品采集和年代测试,发现东侧和中间的断层陡坎为正断层所控制,西侧的断层陡坎为逆断层所控制;③探槽开挖揭露出晚更新世晚期以来,临泽断裂上发生过4次古地震事件,时间分别为(8895±125) aB.P.之前、(7 245±75)a B.P.～(6 190±20) aB.P.、(5120±20) aB.P.～(4.8±0.5)ka和(2 550±50) aB.P.～(2 326±64)a;④全新世以来可以确定3次事件,较早一次事件与榆木山北缘断裂上较早一次古地震事件时间比较吻合,说明临泽断裂可能是榆木山断裂向河西走廊内部继续活动的延伸;最后一次古地震事件的离逝时间约为2500 a,表明临泽断裂全新世活动一直比较强烈.

通过卫星影像解译和野外实地调查,获得滇西南地区孟连断裂的几何特征和活动性参数.孟连断裂总体走向NE-NEE向,不具有明显的分段性,连续性较好.断裂从单侧控制着沿线的勐滨、孟连和勐马三个新生代盆地的发育.断裂沿线地貌以线性较好的断层谷、断层崖和断层陡坎为主,并发育多级左旋位错的河流、冲沟和阶(台)地等,观测到的最小左旋位错约为7 m.采用高精度Li-DAR测量方法,对4处典型水平位错地貌进行精细测量,根据获得的相应地貌面年代,得到孟连断裂晚第四纪以来平均左旋走滑速率为2.2±0.4 mm/a.其结果与滇西南地区其他NE向左旋走滑断裂滑动速率相当,反映了区域构造活动的整体协调性.根据跨断层地质体最大左旋位错量9.5±1.8 km,估算断裂开始左旋走滑的时代为距今4.7±1.6 Ma左右,即中新世中晚期.

The Qinghai Nanshan is located interior of northeastern Tibetan Plateau, extending W-E trending for 200 km between the Ela Shan and Riyue Shan, constituting the northern boundary of the Gonghe Basin. Qinghai Nanshan is very important to understand the Qinghai lake Basin-Gonghe Basin landscape evolution process, and it also provides a clue to understand the deformation of northeastern Tibetan Plateau. Our study focuses on identifying the unrecognized segment of the Qinghai Nanshan fault along the Gonghe Basin by applying river longitudinal profiles, and geomorphic indices such as stream length (SL) gradient index and mountain front sinuosity (S-mf), as well as combining the field investigation. The results show that the anomalies of river longitudinal profiles in their upper reach may result from lithological contact, whereas the pronounced convex and deflection that occurred especially in the mid-reach are most likely related to recent tectonic activities caused by the Qinghai Nanshan thrust fault. Moreover, SL values are in agreement with the anomalies shown by the longitudinal profiles. Combining the results of geomorphic indices and topography analysis, as well as the field investigation, we project the distribution of the Qinghai Nanshan fault and discussed the tectonic implications. The listric Qinghai Nanshan thrust fault and the influences from the Elashan and Riyueshan dextral strike-slip faults are controlling factors for landscape of the Qinghai Nanshan.

The Altyn Tagh fault is the northern boundary of Tibetan Plateau. As one of the most well-known strike-slip fault in the world, great achievements on tectonic deformation and Late Quaternary slip rate have been made. However, there is a long-lasting debate on whether the Altyn Tagh fault extends into the Jinta Basin or even eastward. In this paper, we use satellite image interpretation, field investigation, trench excavation, and optical stimulated luminescence dating to study newly found NS striking scarps in the eastern end of Jinta Nan Shan. The results are as follows: firstly, a group of normal faults develop on terrace T2 of Heihe River, the total length amounts to ∼40 km, total scarp height is 30±5 m; secondly, four paleoseismic events have been interpreted from three trenches, approximate ages of events are 79.97±19.14 ka BP, 62.55±13.10∼55.41±10.77 ka BP, before 16.89±2.08 ka BP, 8.52±1.49 ka BP, respectively; thirdly, just like NS normal faults in the western end of Altyn Tagh fault, the newly found NS extensional faults are likely the terminating tectonics of the eastern end of Altyn Tagh fault, the large Altyn Tagh fault may end in the eastern end of Jinta Nan Shan.

金塔南山断裂位于河西走廊酒泉盆地北侧,是青藏块体与阿拉善块体的边界断裂之一.前人仅对该断裂西段开展过古地震研究.文中基于古地震探槽研究和光释光测年等传统地震地质工作方法,定量研究了金塔南山断裂中东段的古地震特征.通过对断裂进行系统的野外调查,发现沿断裂沿线地层以早更新世至晚更新世洪积物为主,全新世洪积物厚度仅几十cm.选取发育在全新世洪积物相对较厚的洪积扇上的断层陡坎进行工作,获得了一些初步的认识:金塔南山断裂中东段晚第四纪以来持续活动特征明显,全新世洪积扇上发育高0.5～1m的断层陡坎表现出了很新的活动性.多个探槽揭露出晚更新世晚期以来的4次古地震事件,分别发生在(15.16±1.29) ka之前、(9.9±0.5) ka之前、6ka左右、(3.5±0.4)ka之后.全新世中期以来,发生过2次事件,且2次古地震均造成断裂全段破裂.

A series of NWW striking faults are obliquely intersected by the NEE striking Altyn Tagh fault zone in the western Qilian Mountains.These faults were mostly active in late Quaternary and play an important role in accommodating regional lateral extrusion by both reverse and sinistral slip.Detailed studies on late Quaternary activity,tectonic transformation,paleoseismology,and strain partitioning not only significantly affect our recognition on seismogenic mechanism and zones of potential large earthquakes,but also provide useful information for exploring tectonic deformation mechanism in the northern Tibetan plateau.The Danghenanshan Fault,Yemahe-Daxueshan fault,and Altyn Tagh Fault form a triplet junction point at southwest of Subei county.The Yemahe-Daxueshan fault is one important branch fault in the western Qilian Mountains that accommodated eastward decreasing slip of the Altyn Tagh Fault,which was active in late Holocene,with a length up to 170km.Based on geometry and late Quaternary activity,the Yemahe-Daxueshan fault was subdivided into 3 segments, i.e.the Subei fault,Yemahe fault and Daxueshan Fault.The Yemahe Fault has the most prominent appearance among them,and is dominated by left-lateral slip with a little normal component.The heights of fresh scarps on this fault are only several tens of centimeters.We dug 2 trenches at the Zhazhihu site,and cleaned and reinterpreted one trench of previous studies.Then we interpreted trench profiles and paleoseismic events,and collected 14C and Optical Stimulated Luminescence samples to constrain event ages.Finally,we determined 3 events on the Yemahe fault with ages (6 830±30)a BP-(6 280±40)a BP,(5 220±30)a BP,(2 010±30)a BP,respectively.The elapsed time of most recent earthquake is(2 010±30)years before present,which is very close to the recurrence interval,so the possibility of major earthquakes on the Yemahe fault is relatively large.

Three-dimensional scanning with LiDAR has been widely used in geological surveys.The LiDAR with high accuracy is promoting geoscience quantification.And it will be much more convenient,efficient and useful when combining it with the Unmanned Aerial Vehicle(UAV).This study focuses on UAV-based Laser Scanning (UAVLS)geological field mapping,taking two examples to present advantages of the UAVLS in contrast with other mapping methods.For its usage in active fault mapping,we scanned the Nanpo village site on the Zhangxian segment of the West Qinling north-edge fault.It effectively removed the effects of buildings and vegetation,and uncovered the fault trace.We measured vertical offset of 1.3m on the terrace T1 at the Zhang river.Moreover,we also scanned landslide features at the geological hazard observatory of Lanzhou University in the loess area.The scanning data can help understand how micro-topography affects activation of loess landslides.The UAVLS is time saving in the field,only spending about half an hour to scan each site.The amount of average points per meter is about 600,which can offer topography data with resolution of centimeter.The results of this study show that the UAVLS is expected to become a common,efficient and economic mapping tool.

The Subei Fault is located in the western part of the Yema River-Daxue Mountain fault, which is located in the northeast of the Tibetan Plateau.This fracture is about 17 km long, trends northwest 40°, and crosses the Altyn Tagh Fault in the Subei area.The conventional view is that the power of the Altyn Tagh Fault with a high slip rate (about 10 mm/a) was absorbed by the Tanghe Nan Shan fault, the Yema River-Daxue Mountain fault, the Changma fault, and so on.Some of this power was also tranversed to form a thrust fault, after which the slip rate of the Altyn Tagh Fault decreased to 1~2 mm/a.There has been little formal research and no systematic study made of the late Quaternary activity along the Subei Fault.Using high-resolution satellite imagery and systematically studying the Subei Fault area, we generated complete geology maps of the Subei area at a scale of 1∶25,000 and some maps at a scale of 1∶5,000.In addition, we completed other tasks, including a trench study, 14C sample dating, and measurements made by small unmanned aerial vehicles (sUAVs).Our conclusions are as follows: The Subei fault is a Holocene thrust fault that has exhibited multiple-staged activity since the late Quaternary, based on the structure transform mode put forward by Xu Xiwei in 2003.Moreover, our study shows the sUAV to have broad application prospects.We can rebuild a digital elevation mode based on hundreds of pictures collected by sUAVs with a very high precision.Using this technology, we can also build digital orthoimages any places we wish.Using digital elevation models (DEMs), we chose typical landforms and extracted their profiles to show the altitude of the scarps.We compared the altitudes measured by the DEM profile with measurements by the laser range finder, and found the measurement results to be basically the same.Combining several fault profiles along the Subei Fault and that of a trench excavated in Xishuigou, we determined that the Subei Fault is mainly a thrust fault, with linear and continuous scarps along the fault.

通过卫星影像解译、野外实地调查和地质填图,对滇西南地区的澜沧断裂的最新活动性开展了翔实的调查,重点对该断裂的古地震特征进行了分析,通过中南段3个探槽剖面的详细分析和样品年代测试,对其存在的古地震事件进行了判定,初步确定了6次古地震事件的发生年代,分别为距今约3700 a、2300～2500 a、1 200～2 000 a、900～1 200 a、500～ 600 a和20 a.古地震具有周期复发的特征,其复发间隔为500～600 a.