新疆柴窝堡盆地南缘断层晚第四纪的最新活动和滑动速率

通过航、卫片解译和野外实地踏勘对新疆柴窝堡盆地南缘断层晚第四纪以来的活动特征及活动速率方面有了新的认识:研究认为该断层晚第四纪以来曾有过强烈的活动,断层最新活动在南台子断错乌鲁木齐河Ⅰ级阶地的全新世砂土卵砾石层,形成20～40 cm的垂直断距,在柴窝堡盆地盐湖以南断错冲沟河流Ⅱ级阶地的晚更新世砾石层,垂直断距大于9 m,初步估算晚更新世以来该断层的垂直活动速率为0.09 mm/a,引起的水平缩短速率为0.5 mm/a.作为柴窝堡盆地南缘断层分支的板房沟断层,其最新活动的证据是断错了乌鲁木齐河Ⅰ级阶全新世砾石层.     

青海热水-日月山断裂带的新活动特征

热水 -日月山断裂带是发育在青藏高原东北缘柴达木 -祁连活动地块内部的 1条重要的NNW向逆 -右旋走滑活动断裂带 ,长约 183km。断裂由 4条不连续的次级断裂段右阶羽列而成 ,阶距 2～ 3km左右 ,在不连续部位形成拉分区。主断裂两端则形成帚状分叉。断裂活动形成了一系列山脊、冲沟和阶地等右旋断错微地貌 ,其中Ⅰ级阶地右旋断错约 8～ 11m ,Ⅱ级阶地右旋断错约 35m。同时沿断裂带还形成了许多断层陡坎 ,Ⅰ级阶地或洪积台地上断层陡坎高约 0 .5～ 1m ,最高达 2 .8m ,Ⅱ级阶地或台地上的断层陡坎高约 2 .5～ 3m ,最高达 4～ 5m。根据相应的阶地年代 ,计算得到断裂带全新世以来的平均水平滑动速率为 3 16mm/a ,垂直滑动速率为 0 .83mm/a     

罗云山山前断裂带阶地调查研究及其构造意义

罗云山山前断裂带位于山西临汾盆地西侧,控制着盆地的西界.对罗云山山前断裂带8条冲沟的阶地测量资料的研究表明:该断裂带冲沟发育T1～T5五级阶地.T1 阶地拔沟3m左右,T2 阶地拔沟8～10m,T3 阶地拔沟20m左右,T4 阶地拔沟30m左右,T5 阶地拔沟40～50m.阶地测年数据及断错地貌调查表明:罗云山山前断裂带在晚第四纪以来有过多次活动.晚更新世中晚期以来阶地的抬升速率为0.41 mm/a,全新世以来抬升速率为0.75mm/a.罗云山山前断裂带冲沟阶地从晚更新世中晚期到全新世抬升速率有逐渐增大的趋势,反映该断裂带自晚第四纪以来构造抬升作用逐渐加强,这与临汾盆地从晚更新世晚期到全新世沉降速率也有增大的趋势比较一致.     

甘加盆地西缘断裂带发现新活动证据

甘加盆地位于西秦岭北缘断裂带西端,盆地西缘发育了三条近南北向的断层（东支、中支、西支）,表现为西高东低的弧形地貌阶梯带。基于高分辨率卫星遥感影像解译、地质地貌调查、UAV航拍测量、剖面清理与¹⁴C测年等工作,对甘加盆地西缘断裂带进行综合研究,发现该断裂带第四纪晚期有新活动。断层新活动在地貌上表现为不同级别的断层陡坎、阶地与洪积台地断错以及冲沟与阶地右旋等特征。断层剖面与擦痕揭示,该断裂带具右旋逆冲性质,断层断错最新地层为全新统。根据测量与测年数据,初步估算甘加盆地西缘断裂带西支全新世中期以来的平均水平右旋滑动速率为0.89 mm/a,平均垂直滑动速率为0.30 mm/a。     

库车坳陷东秋里塔格断裂晚第四纪活动和滑动速率

东秋里塔格断裂是库车坳陷内活动最为强烈的断裂之一,断错了波斯坦托克拉克河两岸的各级阶地。利用全站仪对河西岸的阶地变形进行了精确测量,得到Ⅰ、Ⅱ、Ⅲ级阶地形成以来东秋里塔格断裂的垂直断错量分别为12.5 m、20 m和24.5 m,并根据前人资料和区域类比的方法对各级阶地年龄进行了估计,计算得到晚第四纪以来该断裂的平均垂直滑动速率为1 mm/a左右,所引起的地壳缩短速率为(1.97~2.13)mm/a。     

祁连山西段酒西盆地区阶地构造变形的研究

对祁连山西段酒西盆地晚第四纪阶地的研究表明,该区早第四纪以挤压褶皱、逆冲为特征的构造变形在晚更新世期间乃至全新世仍继承性地进行着,表现为横穿褶皱和逆断裂带的河流及冲沟阶地面的形成、阶地类型的转变、阶地级数的增多和阶地面被断错或发生拱曲变形．其中祁连山北缘大断裂晚更新世晚期以来的垂直运动速率约为１．９２～２．００ｍｍ／ａ．老君庙背斜逆断裂带在晚更新世初以来的垂直运动速率约为１．１５～２．５６ｍｍ／ａ．白杨河背斜逆断裂带晚更新世初以来的垂直运动速率约为０．３２～０．５８ｍｍ／ａ．     

卡率克阿尔特断裂带活动特征

卡兹克阿尔特断裂带是帕米尔和天山新生代造山带间一个重要的活动构造边界，通过对其活动构造特征的详细地质调查和大比例尺填图，可将卡兹克阿尔特断裂带进一步划分为吉勒格由特断裂带、乌恰地震断裂带和木什断裂带3段。吉勒格由特断裂带的地表破裂为一系列的断层陡坎和偏转的冲积扇，经过别尔托阔依河出山口处时，切割了T1至T3堆积阶地。断裂带在T1、T2和T3阶地的断层陡坎离高度分别为0．67m、3．90m和36．50m。对采自T2阶地顶部和底部的粉砂样品进行光释光测年，测定的初步结果分别为8900aB和10500PaBP，因此对T3、T2阶地以来的滑动速率估计分别约为3．5mm/a、0．8mm/a。断裂的前缘开挖的探槽揭示出全新世以来有4次古地震活动。乌恰地震带主要切割克兹勒苏河的T3阶地地后缘，沿断裂带分布有大小不等的断塞塘和断层陡坎。1985年8月23日乌恰地震上发生Ms7．4地震，地震最大位锚为1．5m。根据断层陡坎计算出断理解的动速度约为0．54mm/a。卡帕河的东岸探槽同样揭示出有4次古地震活动。在乌恰地震带的东端，木什断裂带地表长度约6km,讪数十条左阶排列的反向断层陡坎（坡向北）组成，沿这些断坎多处可见冲沟被断错，横跨断层陡坎的探槽揭示出3次古地震活动。     

卡兹克阿尔特断裂带活动特征

卡兹克阿尔特断裂带是帕米尔和天山新生代造山带间一个重要的活动构造边界,通过对其活动构造特征的详细地质调查和大比例尺填图,可将卡兹克阿尔特断裂带进一步划分为吉勒格由特断裂带、乌恰地震断裂带和木什断裂带3段.吉勒格由特断裂带的地表破裂为一系列的断层陡坎和偏转的冲积扇,经过别尔托阔依河出山口处时,切割了T1至T3堆积阶地.断裂带在T1、T2和T3阶地的断层陡坎高度分别为0.67m、3.90m和36.50m.对采自T2阶地顶部和底部的粉砂样品进行光释光测年,测定的初步结果分别为8900aBP和10500aBP,因此对T3、T2阶地以来的滑动速率估计分别约为3.5mm/a、0.8mm/a.断裂的前缘开挖的探槽揭示出全新世以来有4次古地震活动.乌恰地震带主要切割克兹勒苏河的T3阶地后缘,沿断裂带分布有大小不等的断塞塘和断层陡坎.1985年8月23日在乌恰地震带上发生Ms7.4地震,地震最大位错为1.5m.根据断层陡坎计算出断裂的滑动速率约为0.54mm/a.卡帕河的东岸探槽同样揭示出有4次古地震活动.在乌恰地震带的东端,木什断裂带地表长度约6km,由数十条左阶排列的反向断层陡坎(坡向北)组成,沿这些断坎多处可见冲沟被断错,横跨断层陡坎的探槽揭示出3次古地震活动.     

罗云山山前断裂中段土门-贾朱村晚第四纪断错地貌特征

罗云山山前断裂位于山西临汾盆地西侧,控制着盆地的西界。通过对该断裂1∶ 5万地质填图、对河流冲沟阶地及山前断错地貌的调查,介绍了罗云山山前断裂中段土门-贾朱村晚第四纪断错地貌特征。罗云山山前发育D1、D2、D3 等3 级洪积扇,罗云山山前断裂上升盘冲沟发育T1 ～ T5 等5 级阶地。D1 洪积扇与T1、T2 阶地形成于全新世早中期;D2 洪积扇与T3 阶地形成于晚更新世中晚期;D3 洪积扇与T4、T5 阶地形成于中更新世中晚期。罗云山山前断裂中段不同部位断错地貌特征差异较大,D1 洪积扇的断错在席坊沟一带断距约2. 9m;在金殿镇峪口村南西山前断错约3m。D2 洪积扇的断错在土门镇南西堡子村约2. 5m;在杨家庄村西山前断错约4m;在景村西山前断错约6m;在襄陵镇浪泉沟南西侧山前断错约7. 7m。罗云山山前断裂中段山前断错地貌明显,其最新活动时代为全新世。其中,土门段最新活动时代为全新世早期,龙祠段最新活动时代为全新世中晚期。罗云山山前断裂中段晚更新世中晚期以来活动速率为0. 18～ 0. 54mm / a,由北向南活动呈增强趋势;全新世早中期以来活动速率为0. 4 ～ 0. 9mm / a,断裂活动主要集中于席坊沟-峪口一带。罗云山山前断裂中段从晚更新世中晚期到全新世活动速率有增大的趋势,这与该断裂上升盘冲沟阶地从晚更新世中晚期到全新世抬升速率有增大的趋势以及临汾盆地从晚更新世晚期到全新世沉降速率也有增大的趋势具有较好的一致性。     

山西交城断裂北端及中段3个大型探槽全新世断错现象分析

前人在山西交城断裂带上开挖过多个探槽,揭露出全新世3次古地震事件,但其研究结果尚不能确定该断裂带全新世活动段的北部边界.近期在该断裂带北端和中段又开挖了3个大型探槽,其中在阳曲县泥屯盆地西界开挖的龙王沟探槽,是一个由多个探槽组合成的大探槽,该探槽揭示的地层断错信息,将交城断裂带全新世活动的范围向北延伸了20km.另外2个大型探槽分别为交城断裂带中段瓦窑沟东侧台地前缘的瓦窑探槽与市儿口沟西侧T1阶地前缘的新民探槽.这3个大探槽均揭示出全新世中期(14C测年值为距今5 ～ 6ka)的垆土和淤泥层,以及多组平行分布的断面,所揭示的全新世3次古地震事件具有断错事件活动的同步性,可与前人探槽揭示的全新世断层活动事件相对比.3次断错活动时间分别距今3.06 ～3.53ka、5.32ka左右或6.14ka左右、8.36ka左右;3次事件的时间间隔分别为2.02 ～ 2.84ka和2.22 ～ 3.04ka.这些断错事件的同震垂直位移为1.5～4.7m,显示了7级以上地表破裂型的强震活动.最后讨论了探槽中14C测年样品的影响因素.     

LATE-QUATERNARY GEOLOGICAL EVIDENCE OF JIANQUANZI-BARKOL SINISTRAL FAULT SYSTEM IN EASTERNMOST TIENSHAN

As we all know, Eastern Tienshan and Altaid in central Asia accommodate~10mm/a crustal shortening, accounting for 1/4 shortening between India and Eurasia(~40mm/a). A substantial portion of these deformations was absorbed in Altaid in the north through a combination of right-lateral strike-slip and counterclockwise vertical axis rotation of crustal blocks, but how the crustal deformation was accommodated in Eastern Tienshan is still in debate. Based on the field investigation in Jianquanzi, Barkol Tagh and Karlik Tagh in Eastern Tienshan in recent years, we identified a sinistral strike-slip fault system mapped in Eastern Tienshan. From west to east, the Jianquanzi-Tuolaiquan Fault(JTF), South Barkol Basin Fault (SBF) and Central Karliktagh Fault(CKF)constitute the tectonic frame of this large-scale fault system, which plays an important role in adjusting the strain distribution during the process of orogening in Eastern Tienshan in Quaternary even since Ceonozoic era. The fault system displays different late-Quaternary characteristics when its orientation changes with regional tectonic principal stress(NE). Specifically, the EW-trending JTF exhibits sinistral slip with little vertical component which can extend to Xiongkuer segment on EW-NW-trending SBF. The EW-NW SBF displays sinistral slip from east of Luobaoquanto, Barkol County and reverse slip with little horizontal component at east of Barkol County. In easternmost, the WNW-EW trending CKF shows sinistral slip with no obvious vertical motion. This fault system's activity coupled in the orogenic process of easternmost Tienshan, adjusting and accommodating a portion of deformation included in the orogenic process, and in turn we suggest that the deformation associated with range front fault in the orogen root may not be the only decisive way of deformation releasing.     

THE LATE QUATERNARY ACTIVITY FEATURES AND SLIP RATE OF THE YANGGAO-TIANZHEN FAULT

The Shanxi Graben System is one of the intracontinental graben systems developed around the Ordos Block in North China since the Cenozoic, and it provides a unique natural laboratory for studying the long-term tectonic history of active intracontinental normal faults in an extensional environment. Comparing with the dense strong earthquakes in its central part, no strong earthquakes with magnitudes over 7 have been recorded historically in the Jin-Ji-Meng Basin-and-Range Province of the northern Shanxi Graben System. However, this area is located at the conjunction area of several active-tectonic blocks(e.g. the Ordos, Yan Shan and North China Plain blocks), thus it has the tectonic conditions for strong earthquakes. Studying the active tectonics in the northern Shanxi Graben System will thus be of great significance to the seismic hazard assessment. Based on high-resolution remote sensing image interpretations and field investigations, combined with the UAV photogrammetry and OSL dating, we studied the late Quaternary activity and slip rate of the relatively poorly-researched Yanggao-Tianzhen Fault(YTF)in the Jin-Ji-Meng Basin-and-Range Province and got the followings: 1)The YTF extends for more than 75km from Dashagou, Fengzhen, Inner Mongolia in the west to Yiqingpo, Tianzhen, Shanxi Province in the east. In most cases, the YTF lies in the contact zone between the bedrock mountain and the sediments in the basin, but the fault grows into the basin where the fault geometry is irregular. At the vicinity of the Erdun Village, Shijiudun Village, and Yulinkou Village, the faults are not only distributed at the basin-mountain boundary, we have also found evidence of late Quaternary fault activity in the alluvial fans that is far away from the basin-mountain boundary. The overall strike of the fault is N78°E, but the strike gradually changes from ENE to NE, then to NWW from the west to the east, with dips ranging from 30° to 80°. 2)Based on field surveys of tectonic landforms and analysis of fault kinematics in outcrops, we have found that the sense of motion of the YTF changes along its strikes: the NEE and NE-striking segments are mainly normal dip-slip faults, while the left-laterally displaced gullies on the NWW segment and the occurrence characteristics of striations in the fault outcrop indicate that the NWW-striking segment is normal fault with minor sinistral strike-slip component. The sense of motion of the YTF determined by geologic and geomorphic evidences is consistent with the relationship between the regional NNW-SSE extension regime and the fault geometry. 3)By measuring and dating the displaced geologic markers and geomorphic surfaces, such as terraces and alluvial fans at three sites along the western segment of the YTF, we estimated that the fault slip rates are 0.12~0.20mm/a over the late Pleistocene. In order to compare the slip rate determined by geological method with extension rate constrained by geodetic measurement, the vertical slip rates were converted into horizontal slip rate using the dip angles of the fault planes measured in the field. At Zhuanlou Village, the T₂ terrace was vertically displaced for(2.5±0.4)m, the abandonment age of the T₂ was constrained to be(12.5±1.6)ka, so we determined a vertical slip rate of(0.2±0.04)mm/a using the deformed T₂ terrace and its OSL age. For a 50°dipping fault, it corresponds to extension rate of(0.17±0.03)mm/a. At Pingshan Village, the vertical displacement of the late Pleistocene alluvial fan is measured to be(5.38±0.83)m, the abandonment age of the alluvial fan is(29.7±2.5)ka, thus we estimated the vertical slip rate of the YTF to(0.18±0.02)mm/a. For a 65° dipping fault, it corresponds to an extension rate of(0.09±0.01)mm/a. Ultimately, the corresponding extensional rates were determined to be between 0.09mm/a and 0.17mm/a. Geological and geodetic researches have shown that the northern Shanxi Graben System are extending in NNW-SSE direction with slip rates of 1~2mm/a. Our data suggests that the YTF accounts for about 10% of the crustal extension rate in the northern Shanxi Graben System.     

冷龙岭活动断裂的滑动速率研究

根据对冷龙岭断裂重点地段的野外调查,研究了该断裂的几何特征及浮雕劝速率。结果表明：该断裂为一条全新世活动断层,由一组近于平行的次级断裂所组成。按总体特征可将该断裂分为３段,中更新世以来各时代的断裂平均滑动速率分别为：中更新世：２．１４～４．６４ｍｍ／ａ,晚更新世：２．８６～４．０７ｍｍ／ａ,全新世：３．３５～４．６２ｍｍ／ａ,全新世以来该断裂平均垂直滑动速率为０．３８ｍｍ／ａ。     

滇西北通甸-巍山断裂中段的晚第四纪滑动速率

通甸-巍山断裂属于红河断裂带的分支断裂,目前对该断裂中段的晚第四纪活动特征研究较少。野外地质地貌调查和年代学研究结果表明,通甸-巍山断裂中段是以右旋走滑运动为主,兼有张性正断的全新世活动断裂,其最新活动时代距今约2.2ka。晚更新世中晚期以来断裂中段平均水平滑动速率为1.25mm/a,全新世晚期以来垂直运动趋于增强。该研究不仅为该断裂的地震危险性评价工作提供了基础资料,而且有助于理解川滇菱形块体西南边界构造变形的空间分配特点     

DEFORMATION CHARACTERISTICS AND KINEMATIC PARAMETERS INVERSION OF HAIYUAN FAULT ZONE BASED ON TIME SERIES INSAR

Located at the bend of the northeastern margin of Qinghai-Tibet Plateau, the Haiyuan fault zone is a boundary fault of the stable Alashan block, the stable Ordos block and the active Tibet block, and is the most significant fault zone for the tectonic deformation and strong earthquake activity. In 1920, a M8.5 earthquake occurred in the eastern segment of the fault, causing a surface rupture zone of about 240km. After that, the segment has been in a state of calmness in seismic activity, and no destructive earthquakes of magnitude 6 or above have occurred. Determining the current activity of the Haiyuan fault zone is very important and necessary for the analysis and assessment of its future seismic hazard. To study activity of the Haiyuan fault zone, the degree of fault coupling and the future seismic hazard, domestic and foreign scholars have carried out a lot of research using geology methods and GPS geodetic techniques, but these methods have certain limitations. The geology method is a traditional classical method of fault activity research, but dislocation measurement can only be performed on a local good fault outcrop. There are a limited number of field measurement points and the observation results are not equally limited depending on the sampling location and sampling method. The distribution of GPS stations is sparse, especially in the near-fault area, there is almost no GPS data. Therefore, the spatial resolution of the deformation field features obtained by GPS is low, and there are certain limitations in the kinematic parameter inversion using this method. In this study, we obtain the average InSAR line-of-sight deformation field from the Maomaoshan section to the mid-1920s earthquake rupture segment of the Haiyuan earthquake in the period from 2003 to 2010 based on the PSInSAR technique. The results show that there are obvious differences between the slip rates of the two walls of the fault in the north and the south, which are consistent with the motion characteristics of left-lateral strike-slip in the Haiyuan fault zone. Through the analysis of the high-density cross-fault deformation rate profile of the Laohushan segment, it is determined that the creep length is about 19km. Based on the two-dimensional arctangent model, the fault depth and deep slip rate of different locations in the Haiyuan fault zone are obtained. The results show that the slip rate and the locking depth of the LHS segment change significantly from west to east, and the slip rate decreases from west to east, decreasing from 7.6mm/a in the west to 4.5mm/a in the easternmost. The western part of the LHS segment and the middle part are in a locked state. The western part has a locking depth of 4.2~4.4km, and the middle part has a deeper locking depth of 6.9km, while the eastern part is less than 1km, that is, the shallow surface is creeping, and the creep rate is 4.5~4.8mm/a. On the whole, the 1920 earthquake's rupture segment of the Haiyuan fault zone is in a locked state, and both the slip rate and the locking depth are gradually increased from west to east. The slip rate is increased from 3.2mm/a in the western segment to 5.4mm/a in the eastern segment, and the locking depth is increased from 4.8km in the western segment to 7.5km in the eastern segment. The results of this study refine the understanding of the slip rate and the locking depth of the different segments of the Haiyuan fault zone, and provide reference information for the investigation of the strain accumulation state and regional seismic hazard assessment of different sections of the fault zone.     

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.     

HOLOCENE SLIP RATE ALONG THE NE-TRENDING QIXIANG CO FAULT IN THE CENTRAL TIBETAN PLATEAU AND ITS TECTONIC IMPLICATIONS

The two mainstream deformation models of the Tibet plateau are continental escape model and crustal thickening model, the former suggests that the NW-trending Karakoram Fault, Gyaring Co Fault, Beng Co Fault and the Jiali Fault as the Karakoram-Jiali fault zone is the southern border belt and that the dextral strike-slip rate is estimated as up to 10~20mm/yr. However, research results in recent years show that the slip rates along those faults are significantly less than earlier estimates. Taylor et al. (2003)suggest that the conjugate strike-slip faults control the active deformation in the central Tibet. The lack of research on the slip behavior of the NE-trending faults in the central Tibet Plateau constrains our understanding of the central Tibet deformation model. Thus, we choose the NE-direction Qixiang Co Fault located at the north of the Gyaring Co Fault as research object. Based on the interpretation of satellite images, we found several faulted geomorphic sites. Using RTK-GPS ground control point and unmanned aerial vehicle (UAV)topographic surveying, we obtained less than 10cm/pix-resolution digital elevation model (DEM)in the Yaqu town site. We used the LaDiCaoz_v2.1 software to automatically extract the left-lateral offset of the largest gully on the terrace T₂ surface, which is (21.3±7.1)m, and the vertical dislocation of the scarp on the terrace T₂ surface, which is (0.9±0.1)m. The age of both U-series dating samples on the terrace T₂ is (4.98±0.17)ka and (5.98±0.07)ka, respectively. The Holocene left-lateral slip rate along Qixiang Co Fault is (3.56±1.19)mm/a and the vertical slip rate is (0.15±0.02)mm/a. The kinematic characteristics of the sinistral strike-slip with normal slip coincide with the eastward motion of the central Tibet plateau, and its magnitude is in agreement with its conjugate Gyaring Co Fault, suggesting that the deformation pattern of the central Tibetan plateau complies with the conjugate strike-slip faults mode.     

青藏高原东缘礼县-罗家堡断裂带晚更新世以来的活动性分析

礼县 -罗家堡断裂带晚更新世以来有过明显活动。在礼县—罗家堡段和天水镇—街子口段直接错断全新世地层。断裂沿线地表陡坎发育 ,水系被左旋位错。结合沿该断裂带广泛分布的地震滑坡、砂土液化等 ,认为礼县 -罗家堡断裂带是 1654年天水南 8级地震的发震构造。该断裂晚更新世以来的平均水平位错速率为 0 95mm/a ,平均垂直位移速率为 0 35mm/a ,垂直位移速率约为水平位移速率的 1/ 3。这个比值与一次断裂突发性垂直位错量 ( 1 9m)与水平位错量 ( 5 2m)的比值基本吻合     

GEOMETRY AND DEFORMATION TRANSFORMATION OF THE XIMALIN FAULT

The Ximalin fault is the northwest section of the Ximalin-Shuiquan fault, which is part of the north-edge fault zone of the Yanghe Basin, located in the conjunction of the Zhangjiakou-Bohai fault zone and Shanxi fault-depression basin, and its structural geometry and deformation characteristics can facilitate the research on the interaction of the two tectonic belts. In this paper, data of geological surveys and geophysical exploration are used to study this fault exhaustively, concerning its geometry, structural features and activity as well as its relationship with adjacent faults and rule in the deformation transform of the north-edge fault zone of the Yanghe Basin. The results show that the Ximalin Fault is a strike-slip feature with thrust component. Its vertical slip rates are 0.17mm/a and 0.25~0.38mm/a, and the horizontal slip rate is 0.58~0.67mm/a and 0.50mm/a during the late Middle Pleistocene and Holocene, respectively. It is formed alternately by the NW-trending main faults and secondary NE-trending faults, of which the former is characterized by high-angle reverse with sinistral strike-slip, and the latter shows normal faulting. The two sets of structures have specific structural geometry relations, and the motion manners and deformation characteristics match each other. During the active process of the north-edge fault of the Yanghe Basin, the NW trending Ximalin fault played a role similar to a transform fault in deformation change and stress transfer, and its sinistral strike slip activity accommodated the NE trending normal faulting at the both ends.     

南迦巴瓦构造结西侧里龙断裂晚第四纪活动特征

本文通过卫星影像解译、地质地貌调查、地质探槽开挖、断错地貌测量和样品年代学测试,对南迦巴瓦构造结西侧的里龙断裂晚第四纪活动特征进行了分析和研究,结果表明:里龙断裂是一条以右旋走滑活动为主、兼有挤压逆冲的北北西向断裂,其最新活动时代为全新世;该断裂晚第四纪以来的平均水平滑动速率为3-4mm/a,平均垂直滑动速率为0.10-0.15mm/a。研究还表明,南迦巴瓦构造结晚第四纪以来的向北俯冲运动已经停止,喜马拉雅东构造结地区的构造变形主要受阿萨姆构造结的俯冲影响。