武都-康县断裂新活动性的滑动速率

探究武都-康县断裂活动的定量数据有助于更深入地了解甘东南地区构造活动和运动转换关系。基于甘肃省陇南市活断层探测与地质填图研究工作,主要通过遥感影像解译、野外地质调查、断错位移测量等基础方法和手段,对发现的陡坎、水系、河流阶地的位错等重点地貌现象进行差分GPS测量(典型位错点以薛家坡及平洛河沈家沟为例),并收集研究区及邻区白龙江一带相关阶地年代,估算出武都-康县断裂西段平均滑动速率约为1.1mm/a,东段约为1.06mm/a。根据潜在地震最大震级的评估原则与方法,利用震级M-破裂长度L经验公式,计算得到该地区有发生7级地震的可能性。     

活动断裂滑动位移势和滑动速率的评估与地震复发

活动断裂滑动位移势和滑动速率是评价断裂活动程度和估计强震复发周期的两个重要。客观合理地认识它们，对地震预报研究将是十分有益。为缩短断层研究方法在地震职的时间尺度，本文在评价了前人工作的基础上，提出了合理估计这两个参量的几种可能途径。     

酒西盆地内部两条断裂晚第四纪滑动速率研究

通过卫星影像解译、差分GPS测量和地貌年代学样品采集,对位于酒西盆地内部的阴洼山断裂和新民堡断裂晚第四纪滑动速率进行了研究。阴洼山断裂发育于阴洼山东侧,总体走向315°,长约25 km;新民堡断裂整体走向300°,长约20 km,二者皆为全新世活动的逆断层。通过野外考察,选择典型断错地貌进行断层陡坎测量,结合所获相应地貌面的年代数据,得到阴洼山断裂和新民堡断裂晚第四纪垂直滑动速率分别为(0.08±0.02)mm/a和(0.11±0.02)mm/a。结合断裂倾角及前人研究资料,得到垂直祁连山方向酒西盆地内部断裂的地壳缩短速率约为1 mm/a,整个盆地地壳缩短速率约为2.4 mm/a。     

玉川断裂晚更新世以来滑动速率与危险度评定

本文根据野外地震地质调查资料，结合新地层年代测定和断层泥中石英碎砾表面ＳＥＭ显微形貌结构分析，对玉川断裂的滑动速率和危险度进行了讨论，初步认为，该断裂在晚更新世以来右旋走滑活动为主兼顾倾滑活动，平均滑动速率５毫米／年，属Ａ级活断层的Ⅱ－Ⅲ强活动度－中强活动度。逼近时间Ｔ＞２００年，属高危险度。     

乌兰乌拉湖-玉树断裂东段晚第四纪滑动速率

乌兰乌拉湖-玉树断裂是巴颜喀拉地块与羌塘地块分界地带的一条重要活动断裂.该断裂东段晚第四纪以来活动强烈,断错地貌特征明显,为全新世活动的左旋逆冲断裂.利用后差分GPS对阶地与洪积扇断错地貌进行了精细测量,并结合碳十四(14C)和光释光(OSL)测年结果对地貌面年代进行限定,获得该断裂东段晚更新世晚期以来的垂直位错量为5...     

滇西南地区澜沧断裂全新世滑动速率与走滑起始时间探讨

通过卫星影像解译、野外实地调查和地质填图,获得滇西南地区澜沧断裂的基本特征和活动性参数,澜沧断裂属于龙陵—澜沧新生地震断裂带的东南段,北起耿马县联合村,向南东经澜沧县哈卜吗、战马坡、大塘子至澜沧县城东南,总体走向NNW,长度约85km。该断裂为一条全新世活动的右旋走滑断裂,兼具倾滑分量,沿断裂形成了丰富的断错地貌现象,主要表现为断层陡崖、冲沟右旋、断层陡坎、断层沟槽、断层垭口和断陷凹坑等。通过详细的野外考察,选择典型断错地貌进行差分GPS测量,结合所获相应地貌面的年代数据,得到该断裂全新世以来平均右旋走滑速率为(4.2±2.3)mm/a,其结果与现今GPS观测所得速率相当,反映了该断裂长期以来滑动速率的稳定性。同时根据岩体的最大位错量4.6~4.8km,估算断裂开始右旋走滑的时代为距今约1.1 Ma,即早更新世晚期。     

河流阶地演化与走滑断裂滑动速率

断裂滑动速率是活动构造定量研究的最重要参数之一,不仅可以直接应用于活动构造的地震危险性预测和工程场地的地震安全性评价,还为地球动力学研究提供不可缺少的重要信息。原理上,断裂滑动速率可以用总位移量除以其累积时间而获得,但准确地确定断裂滑动速率并不是一件容易的事情,不同方法和研究者测定的同一条断裂的滑动速率可以相差3倍。文中通过对河流基座阶地演化及其对走滑断裂错动响应过程的分析发现,当一条山前河流切入河漫滩使其废弃形成阶地后,断裂的走滑位移使得河流两侧的阶地陡坎都遭到错动,其中一侧的下游阶地陡坎被错入河道而遭到河流的侵蚀,另一侧的下游阶地陡坎被错离河道,受到河流上游右侧地貌的保护而免遭侵蚀。因此,被错离河道一侧的阶地陡坎的位移在上阶地形成时就开始积累,阶地面的暴露年龄相当于位移累积的起始年代。另外,被错离河道一侧的阶地陡坎在下阶地停止侧蚀(可能同时开始接受沉积)时就开始累积位移,下阶地的初始沉积年代也代表阶地陡坎位移开始累积的时间。当然,如果能够获得被位移阶地陡坎的上下阶地年龄,就更能够把滑动速率限定在可靠的范围之内。在上述分析的基础上,提出3种利用河流阶地确定走滑断裂滑动速率的方法:第一是利用上下阶地年龄限定     

祁连山活动断裂带中东段冷龙岭断裂滑动速率的精确厘定

冷龙岭活动断裂是青藏高原东北缘祁连山断裂带的重要组成部分, 位于祁连山断裂带中东段。 根据野外考察结果认为, 该断裂全新世以来活动强烈, 主要表现为左旋走滑运动, 并伴有正倾滑性质, 断错地貌特征明显。 通过高分辨率SPOT卫星数字影像和大比例尺航空照片处理确定断层的位置, 利用断错地貌测图、 热释光(TL)和碳十四(¹⁴C)测年方法, 厘定了冷龙岭断裂的晚第四纪滑动速率, 冷龙岭断裂晚更新世以来的平均水平滑动速率为(4.3±0.7)mm/a, 全新世晚期以来的平均水平滑动速率为(3.9±0.36)mm/a。     

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.     

基于钻探的芦花台隐伏断层晚第四纪活动特征

芦花台断层是银川盆地内一条重要的隐伏构造。在浅层地震勘探成果的基础上,开展了钻孔联合剖面探测和钻孔样品测试,获得了断层上断点埋深、最新活动时代、晚第四纪累计位移和滑动速率等数据。结果表明:芦花台隐伏断层北段和南段的活动性不同,南段为中更新世末活动断层,北段为全新世活动断层;在北段内,断层活动强度在空间上表现为由北向南增强,在时间上表现为晚更新世活动强于全新世。     

THE SLIP RATE AND PALEOEARTHQUAKES OF THE YUMEN FAULT IN THE NORTHERN QILIAN MOUNTAINS SINCE THE LATE PLEISTOCENE

The Yumen Fault lies on the west segment of the north Qilian Fault belt and adjacent to the Altyn-Tagh Fault,in the north margin of the Tibet Plateau.The tectonic location of the Yumen fault is special,and the fault is the evidence of recent activity of the northward growth of Tibetan plateau.In recent twenty years,many researches show the activity of the Yumen Fault became stronger from the early Pleistocene to the Holocene.Because the Yumen Fault is a new active fault and fold belt in the Qilian orogenic belt in the north margin of the Tibet Plateau,it is important to ascertain its slip rate and the recurrence interval of paleoearthquakes since the Late Pleistocene.Using the satellite image interpretation of the Beida river terrace,the GPS measurement of alluvial fans in front of the Yumen Fault and the trench excavation on the fault scarps,two conclusions are obtained in this paper.(1) The vertical slip rate of the Yumen Fault is about 0.41~0.48mm/a in the Holocene and about 0.24~0.30mm/a in the last stage of the late Pleistocene.(2) Since the Holocene epoch,four paleoearthquakes,which happened respectively in 6.12~10.53ka,3.6~5.38ka,1.64~1.93ka and 0.63~1.64ka,ruptured the surface scarps of the Yumen Fault.Overall,the recurrence interval of the paleoseismic events shortens gradually and the activity of the Yumen Fault becomes stronger since the Holocene.Anther characteristic is that every paleoearthquake probably ruptured multiple fault scarps at the same time.     

FAULTED LANDFORM AND SLIP RATE OF THE JINGHE SECTION OF THE BOLOKENU-AQIKEKUDUKE FAULT SINCE THE LATE PLEISTOCENE

The Bolokonu-Aqikekuduke fault zone(Bo-A Fault)is the plate convergence boundary between the middle and the northern Tianshan. Bo-A Fault is an inherited right-lateral strike-slip active fault and obliquely cuts the Tianshan Mountains to the northwest. Accurately constrained fault activity and slip rate is crucial for understanding the tectonic deformation mechanism, strain rate distribution and regional seismic hazard. Based on the interpretation of satellite remote sensing images and topographic surveys, this paper divides the alluvial fans in the southeast of Jinghe River into four phases, Fan1, Fan2, Fan3 and Fan4 by geomorphological elevation, water density, depth of cut, etc. This paper interprets gullies and terrace scarps by high-resolution LiDAR topographic data. Right-laterally offset gullies, fault scarps and terrace scarps are distributed in Fan1, Fan2b and Fan3. We have identified a total of 30 right-laterally offset gullies and terrace scarps. Minimum right-lateral displacement is about 6m and the maximum right-lateral displacements are(414±10)m, (91±5)m and(39±1)m on Fan2b, Fan3a and Fan3b. The landform scarp dividing Fan2b and Fan3a is offset right-laterally by (212±11)m. Combining the work done by the predecessors in the northern foothills of the Tianshan Mountains with Guliya ice core climate curve, this paper concludes that the undercut age of alluvial fan are 56~64ka, 35~41ka, 10~14ka in the Tianshan Mountains. The slip rate of Bo-A Fault since the formation of the Fan2b, Fan3a and Fan3b of the alluvial-proluvial fan is 3.3~3.7mm/a, 2.2~2.6mm/a and 2.7~3.9mm/a. The right-lateral strike-slip rate since the late Pleistocene is obtained to be 3.1±0.3mm/a based on high-resolution LiDAR topographic data and Monte Carlo analysis.     

宗务隆山南缘断裂构造地貌特征与晚第四纪滑动速率

宗务隆山南缘断裂位于柴达木盆地东北缘,是祁连山南缘与柴达木盆地的边界逆断裂,对其晚第四纪活动性进行研究对于理解祁连山地区应变分配模式以及该地区断裂向柴达木盆地内部的挤压扩展过程具有重要意义。文中通过遥感影像解译和野外地质调查,结合GPS地形剖面测量以及宇宙成因核素与光释光定年,对宗务隆山南缘断裂拜京图和蓄集乡等段落开展了详细的研究。综合分析拜京图和蓄集乡地区不同期次洪积扇的垂直位错以及相应地貌面的年龄,得到宗务隆山南缘断裂晚第四纪以来的平均垂直滑动速率为(0. 41±0. 05) mm/a,水平缩短速率为0. 47～0. 80mm/a,约占祁连山地区地壳缩短速率的10%。这些结果有助于进一步理解祁连山地区的应变分配模式以及柴达木盆地北缘地区的构造变形机制。     

GEOMORPHIC FEATURES AND LATE QUATERNARY SLIP RATE OF THE SOUTHERN ZONGWULONG SHAN FAULT

With the continuous collision of the India and Eurasia plate in Cenozoic, the Qilian Shan began to uplift strongly from 12Ma to 10Ma. Nowadays, Qilian Shan is still uplifting and expanding. In the northern part of Qilian Shan, tectonic activity extends to Hexi Corridor Basin, and has affected Alashan area. In the southern part of Qilian Shan, tectonic activity extends to Qaidam Basin, forming a series of thrust faults in the northern margin of Qaidam Basin and a series of fold deformations in the basin. The southern Zongwulong Shan Fault is located in the northeastern margin of Qaidam Basin, it is the boundary thrust fault between the southern margin of Qilian Shan and Qaidam Basin. GPS studies show that the total crustal shortening rate across the Qilian Shan is 5~8mm/a, which absorbs 20% of the convergence rate of the Indian-Eurasian plate. Concerning how the strain is distributed on individual fault in the Qilian Shan, previous studies mainly focused on the northern margin of the Qilian Shan and the Hexi Corridor Basin, while the study on the southern margin of the Qilian Shan was relatively weak. Therefore, the study of late Quaternary activity of southern Zongwulong Shan Fault in southern margin of Qilian Shan is of great significance to understand the strain distribution pattern in Qilian Shan and the propagation of the fault to the interior of Qaidam Basin. At the same time, because of the strong tectonic activity, the northern margin of Qaidam Basin is also a seismic-prone area. Determining the fault slip rate is also helpful to better understand the movement behaviors of faults and seismic risk assessment.Through remote sensing image interpretation and field geological survey, combined with GPS topographic profiling, cosmogenic nuclides and optically stimulated luminescence dating, we carried out a detailed study at Baijingtu site and Xujixiang site on the southern Zongwulong Shan Fault. The results show that the southern Zongwulong Shan Fault is a Holocene reverse fault, which faulted a series of piedmont alluvial fans and formed a series of fault scarps.The 43ka, 20ka and 11ka ages of the alluvial fan surfaces in this area can be well compared with the ages of terraces and alluvial fan surfaces in the northeastern margin of Tibetan Plateau, and its formation is mainly controlled by climatic factors. Based on the vertical dislocations of the alluvial fans in different periods in Baijingtu and Xujixiang areas, the average vertical slip rate of the southern Zongwulong Shan Fault since late Quaternary is(0.41±0.05)mm/a, and the average horizontal shortening rate is 0.47~0.80mm/a, accounting for about 10% of the crustal shortening in Qilian Shan. These results are helpful to further understand the strain distribution model in Qilian Shan and the tectonic deformation mechanism in the northern margin of Qaidam Basin. The deformation mechanism of the northern Qaidam Basin fault zone, which is composed of the southern Zongwulong Shan Fault, is rather complicated, and it is not a simple piggy-back thrusting style. These faults jointly control the tectonic activity characteristics of the northern Qaidam Basin.     

阿尔金断裂带东段第四纪以来的水系位错与滑动速率

从阿克塞西红崖子向东经肃北至红柳峡口长约 150km的范围内 ,通过沟、脊位错的分级与相关阶地年龄测试分析 ,将第四纪以来的水系位错量分为 8级 ,并分别给出其形成年龄 ,得到各时段的断裂滑动速率介于 4 .7～ 6.7mm/a ,平均值 6.0mm /a,局部段落某个时段内最高滑动速率值7.7mm/a。位错量与滑动速率的空间分布有中间大、两头小的特点 ,这可能表明破裂从中间向两端发展的过程 ;在时间上 ,上新世以来的滑动速率比其它各个时段都大 ,这可能与青藏地块在距今 5Ma以来的快速隆升及大规模挤出运动相关。资料表明 ,断裂破裂有从主体断裂某一段落扩展到邻近地带 ,最后又回到主体断裂其它段落的时空演化过程     

银川隐伏断层钻孔联合剖面探测

为获取银川隐伏断层近地表断错、上断点埋深、最新活动时代及滑动速率等信息,在浅层地震勘探基础上,沿断层自北向南横跨主断层布施了新渠梢、满春和板桥3条钻孔联合剖面,确定了主断层在3条剖面上的准确位置,获得主断层上断点埋深分别为5·18~8·30m(新渠梢)、5·01~6·50m(满春)和10·0~13·59m(板桥)。结合测年数据分析:新渠梢剖面断层全新世活动,晚更新世末期以来滑动速率为0·14mm/a;满春剖面断层也是全新世活动,但晚更新世末期以来滑动速率为0·05mm/a;板桥剖面断层全新世不活动。综合地震勘探资料进一步分析认为,以银古路为界,目标区银川隐伏断层分南北2段:北段属全新世活动断层,且自北向南活动强度呈减弱趋势,南段属晚更新世末期活动断层;北段活动强度显著大于南段     

龙陵-瑞丽断裂(南支)北段晚第四纪活动性特征

遥感影像解译和野外地质地貌调查表明,龙陵-瑞丽断裂(南支)北段是以左旋走滑为主兼张性正断的区域性活动断裂。根据一些断错地貌点的大比例尺填图、实地测量及其年代学分析,确定了该断裂为全新世活动断裂,断裂晚更新世以来的平均水平滑动速率为2.2mm/a,平均垂直滑动速率为0.6mm/a;全新世以来的平均水平滑动速率为1.8～3.0mm/a,平均垂直滑动速率为0.5mm/a。断裂晚更新世以来的滑动速率在不同的时间尺度上变化不大,反映了该断裂晚更新世以来的活动强度比较平稳     

VERTICAL SLIP RATE OF MINLE-DAMAYING FAULT INDICATED BY SCARPS ON TERRACES OF DONGDA RIVER

The Qilianshan north-edge thrust (QNT)is located at the boundary between the northern margin of the Qilianshan mountain and Hexi Corridor, with a length over 700km. The Minle-Damaying fault (MDF), trending NWW, is part of the eastern section of the QNT, cutting through the Minle and Wuwei Basins. Hexi Corridor is a region of intense seismic activities, where many large earthquakes have been documented in history, such as the M7.5 Gaotai earthquake in 180, M8.5 Haiyuan earthquake in 1920, M8.0 Gulang earthquake in 1927 and the M7.6 Changma earthquake in 1932. While, there is no seismic record on the MDF. The Dongda River flows across the MDF from south to north. One of the tributary of the Dongda River, Xie River, has very well preserved terraces (T₆-T₁)which were offset by the MDF. On these terraces, there is clear trace of scarps, of which the height increases from terraces T₃ to T₆, indicating an accumulation of offset with time. In order to acquire the cross-section of scarps, unmanned aerial vehicle (UAV)scanning was implemented. With a digital camera mounted on, the UAV scanned an area of 0.52km² and digital elevation model (DEM)was generated with an accuracy of 0.2m vertically. The Thompson's method was utilized to conduct linear regressions on both the hanging wall and foot wall of the fault. The difference between the intercepts of the regression lines with the vertical line going through the intersection of the scarp surface on the fault surface is considered as the vertical offset. Terraces from T₆ to T₃ are very well preserved where MFD intercepts the Xie river, while T₂ and T₁ are badly eroded at the same location. Utilizing the cross-sections extracted from high resolution DEM, we estimate that the vertical offsets of T₆-T₃ are 13.26~15.67m, 9.74~10.13m, 5.86~7.35m and 5.03~5.60m, respectively, with 95%confidence interval. From the offsets of terraces, at least 4 paleo-seismic events are indentified. Terraces were dated by the AMS ¹⁴ C dating, yielding ages (cal BP)of T₆-T₂ as (16 405±210)a, (111 975±21)a, (5 697.5±210)a, (4 470.5±54.5)a and (3 137.5±77.5)a. Liner regression was performed for the relation between the ages and the offsets of terraces, resulting in the average vertical slip rate of MDF since the formation of T₆ as 0.91 average v. As the dip of MDF is about 35°, the shortening rate is estimated to be (1.3±0.13)mm/a. This study provides important parameters for the analysis of seismic activity in heavily populated Minle and Yongchang areas.