河套断陷带大青山山前断裂晚第四纪古地震完整性研究

通过沿大青山山前断裂 18个探槽的古地震分析 ,分别确定了 5个段落的 2 2次古地震事件。呼和浩特段 ,距今约 1.9万a以来 7次 ,平均重复间隔时间 (2 4 6 2± 4 13)a ;毕克齐段距今 2 .2万a以来 4次 ;土左旗西段距今 1.1万a以来 4次 ,平均重复间隔时间 (2 94 8± 5 6 0 )a ;土右旗西段距今约 1.1万a以来 5次 ,平均重复间隔时间 (2 2 89± 36 0 )a ;包头段距今 2 .3万a以来 2次。由断层位移量限定法和多探槽校验法判定 ,大青山山前断裂已揭露的古地震事件还不完全代表晚第四纪全断裂的大地震活动历史。只有在呼和浩特段 1.9万a以来、土左旗西段和土右旗西段约 1.1万a以来活动历史基本完整。其它两个段落不完整。这是用这些古地震资料评价该断裂未来地震危险性 ,以及今后进一步工作时应注意的问题。     

基于河流裂点序列研究秦岭北缘断裂强震活动历史

河流裂点的发育是瞬时不均衡地貌系统最为典型的特征之一,而引发地表破裂的地震活动是造成河流裂点形成的主要成因之一,在河流纵剖面调整的过程中裂点会不断地向上游迁移,以达到新的均衡状态,因此通过识别活动断层上游河道纵剖面中的河流裂点序列可以反推该断层的强震活动历史。秦岭北缘断裂是限定秦岭山体和渭河盆地的重要边界断裂,受制于技术方法和自然条件,对于该断裂全新世地震活动历史一直有待突破。本研究在前人对秦岭北缘断裂分段性研究的基础上选取最为活跃的中段（眉县-蓝田县）,基于资源三号卫星立体像对制作了5 m分辨率和高程精度1.5 m的数字高程模型,在此基础上提取了46条横穿秦岭北缘断裂的河床纵剖面,共识别了108个由断层活动导致的河流裂点。通过分析推断最新一级河流裂点的形成与公元前1000 a的地震相关,进而利用河流裂点的后退速率推断出第2级河流裂点和第3级河流裂点形成的时间距今5624～7425 a和8432～10691 a,如果认为上述河流裂点均由地震所致,那么河流裂点的形成时间就可以代表地震的发生时刻,表明秦岭北缘断裂具有准周期的发震特点,发震周期为2800～4000 a。这一结果与前人针对秦岭...     

曲江断裂南东段全新世滑动速率

高精度SPOT卫星影像和野外地质调查表明,曲江断裂南东段断错山前冲沟及河流Ⅰ级和Ⅱ级阶地,在探槽中见到断裂断错全新世地层,是一条右旋走滑的全新世活动断裂,兼有逆冲性质,断裂的最新活动是1970年通海7.8级地震。对曲江断裂典型走滑断错地貌进行研究,曲江断裂南东段在五街一带水平滑动速率为(3.36±0.1)mm/a,白林山一带水平滑动速率为(3.21±0.3)mm/a。     

大青山山前断裂带中、晚全新世活动的发现

大青山山前断裂带位于大青山南麓,为河套断裂系的重要组成部分。该断裂带控制大青山山体的抬升和呼和断陷的形成,地貌特征十分明显,第四纪断层十分发育。大青山山前断裂带第四纪强烈活动,但有关全新世活动的确凿证据未能肯定,亦未见有报道。近年来,我们在包头东河区至沙尔沁一带,发现含全新世文化层的坡、洪积地层多处被错断,证实大青山山前断裂带中、晚全新世活动仍较显著,这对研究河套地区可能存在古地震遗迹提供了重要的线索。     

内蒙古包头市区大青山山前断裂地震活动断层初步研究

通过多年来野外考察及断层活动事件年代测定,现已初步查明,包头市区座落在大青山山前断裂西段全新世地震活动断层上。该地震活动断层展布于山前Ⅱ级或Ⅰ级台地前缘,由一系列地震断层、地震陡坎、地震崩积楔、地震充填楔、地裂缝及沙土液化等地震形变遗迹组成,构成规模较大、连续性好的地震地表破裂带。地震断层呈直线型或宽缓弧形斜列延伸,错断全新统及最新地貌面,为一系列断面向南倾斜的正断层及阶状正断层,断层面平整,具垂直擦痕,断层带往往为砂砾、角砾或沙土充填,显示为主要在张应力作用下断层经历5次活动、正倾滑运动而形成。最新一次活动事件为公元849年地震。根据对全新世地震活动断层的活动特征、活动期次的划分及强震复发间隔的初步研究,以及历史和现今地震活动规律的研究,包头市区地震危险性应该引起相当的关注。     

西南天山柯坪推覆系西段全新世构造活动特征和古地震

柯坪推覆系是南天山重要的多排逆断裂推覆系,研究其活动性对讨论天山新生代构造具有重要意义。讨论柯坪推覆系全新世以来的活动特征和古地震情况可以对其最新活动性特点做出评价。通过对柯坪推覆系西段三排褶皱冲断带山前地貌面上断层陡坎的精确测量和典型地点的古地震探槽研究,并通过~(10)Be宇宙成因核素方法确定地貌面时代和古地震发生时间。获得的结果表明全新世以来柯坪推覆系西段的西柯坪塔格断裂、奥兹塔格断裂和托克塔格断裂的活动速率分别为1.45(+1.68/-0.44)mm/a,0.81(+0.35/-0.19)mm/a和(0.3±0.05)mm/a。表现出天山多排逆断层前展模式中活动强度由后排构造向前排构造转移的特点;古地震的位移量和复发周期特点与活动速率相似,前排古地震活动性强于后排,产生较大地表破裂的强震多出现在第一排的柯坪塔格断裂上。其中第一排西柯坪塔格断裂2次地震复发间隔约4 ka,单次地震位移量约3 m;第二排奥兹塔格断裂4次地震复发间隔约2 ka,单次地震位移量约1 m;第三排托克塔格断裂7 ka来仅发生过1次地震。皮羌捩断层是柯坪推覆系东西段前展推覆速率差异的构造结果。推覆系西段的变形速率明显强于东段,造成推覆系统整体沿皮羌捩断层撕裂。同时由于前展模式的构造特点,目前皮羌断裂两侧的后排断层已经存在近20 km的巨大错距,而随着活动速率向前排的转移,前排两侧4km左右的错距正在增大。     

昔格达断裂晚第四纪活动特征及强震复发周期

利用冲沟、山脊等断错构造地貌的DEM影像资料和详实的野外踏勘,详细分析了昔格达断裂的晚第四纪活动特征。结果显示:断裂线两侧的河沟和山脊地貌呈"S"或反"Z"形或以多个首尾连接的"S"形雁列式斜列,断裂活动为左行左列式,断层上发育多个拉分盆地和断裂湖;该断裂最新活动时间晚于(12.83±1.09)ka,为全新世走滑活动断裂,倾滑分量不大,倾向总体西倾,且晚更新世以来的左旋走滑速率约为1.70 mm/a;依据断裂线地震遗迹及断裂活动特征,断裂强活动复发间隔大致为10~12 ka或更短。     

酒西盆地内部白杨河逆断裂-褶皱构造变形

祁连山各个山前盆地内发育了大量断裂和褶皱,是青藏高原向北扩展的重要表现形式。对这些断层和褶皱的研究有助于探讨青藏高原向北扩展和隆升的机制问题。酒西盆地是位于祁连山最西端的山前坳陷盆地,其内部正在发育最新生的白杨河逆断裂-褶皱带。本文通过对白南断裂-白杨河背斜的地质调查、阶地测量以及探槽开挖工作,对酒西盆地内部最新生的白杨河逆断裂-褶皱得到了几点认识:①白杨河逆断裂-褶皱是酒西盆地内新生的逆断裂-褶皱,是酒西盆地边界断层无法完全吸收青藏高原向北扩展的变形量所产生的次级构造。②白南断裂-白杨河背斜符合断层相关褶皱中的断弯褶皱模型,并存在膝折带迁移的现象。③白杨河背斜的起始隆升时间在中更新世后期,即距今300ka左右,平均隆升速率约0.21mm/a;构造强度有逐渐增大的趋势,全新世以来隆升速率约0.36~0.5mm/a。④白南断裂是全新世活动断裂,全新世以来发生过至少2次古地震。在近1ka以来至少存在一次最新的古地震事件。     

河套盆地北缘色尔滕山河流地貌参数特征及其成因分析

地貌形态是构造和地表过程相互作用的复杂产物,主要通过构造活动和岩石的抗侵蚀能力等来调节。构造活动相对较弱的古老造山带往往可以忽略构造驱动的岩石抬升,使得研究岩石抗侵蚀能力对其地貌雕刻的贡献成为可能。但是目前大多数活动造山带地貌研究的结果显示地貌主要受控于活动构造,关于岩性对地貌演化影响的报道较少。色尔滕山山前断裂为河套盆地北缘的一条重要控盆断裂,全新世以来该断裂的活动性较强,曾发生过两次较大震级地震（M6. 4和M5. 9）。前人活动构造研究表明该断裂的活动性具有空间差异,中部乌加河镇活动性最强,两端逐渐减弱。但相对河套盆地北缘其他大型断裂（如狼山山前断裂、乌拉山北缘断裂和大青山山前断裂）,该断裂的地貌参数研究较少。同时其地貌演化特征及发育机理仍然不清楚,这些均制约了对该断裂的变形动力学理解。本文基于30 m分辨率的DEM数据对该断裂进行详细的河流地貌学参数研究,包括使用Arcgis和Matlab脚本提取色尔滕山山前33条河流的子流域盆地面积 高程积分（HI）和相应河道陡峭指数（Ksn）、河道纵剖面及其裂点等地貌学参数。结果表明研究区河流HI值大部分处于0. 40~0. 66之间,其中乌加河镇附近具有高值,流域盆地处于发育的壮年期。瞬态河道和稳态河道均沿着色尔滕山山前断裂走向分布,可能表明色尔滕山山前大部分河道目前处于瞬时地貌向均衡地貌演化阶段,并且通过对比发现瞬态河道裂点成因存在岩性和构造共同控制的现象。河道陡峭指数空间分布差异性较大,乌加河镇附近（S13~S20）陡峭指数较大,向两边陡峭指数逐渐减小,在S8河流以西又有增大的趋势。通过结合岩性和降雨情况分析发现,河道陡峭指数除了受岩性抗侵蚀能力影响外,其分布还与色尔滕山山前断裂垂直滑移速率分布和垂直位错分布基本一致。综合来看,地貌参数的空间分布是岩性差异和色尔滕山山前断裂活动分段差异性共同控制的结果,表明该地区岩性和构造对地貌的协同塑造作用。     

山西地堑系北部六棱山北麓断裂西段晚第四纪右旋走滑速率的约束

山西地堑系是华北中部的一个不连续的右旋剪切拉张构造带,这一观点似乎早已被学界所广泛认同。然而,目前仍缺乏对山西地堑系内部NNE向断裂右旋走滑特征的深入认识。本研究主要以山西地堑系北部六棱山北麓断裂的西段为研究对象,基于高分辨率卫星影像解译、野外地质地貌调查、无人机摄影测量和光释光测年等手段对断裂的晚第四纪运动学特征进行了厘定。跨断裂冲沟的一致性右旋偏转等表明断裂具有右旋走滑活动,断裂露头的构造解析及断层三角面、断层崖和冲沟裂点等指示断裂还具有正断分量。对断错地貌面和地质体的精确测量结果表明断裂应以右旋走滑为主,兼有正断分量,且走滑分量远大于垂直分量。结合年代学估算出断裂晚第四纪以来的右旋走滑速率为1.6±0.3 mm/a,垂直滑动速率约为0.2 mm/a。六棱山北麓断裂西段的右旋走滑速率与GPS测量的山西地堑系的右旋剪切速率大体相当,表明六棱山北麓断裂西段在山西地堑系的右旋剪切运动中起着重要的作用。六棱山北麓断裂西段的右旋走滑运动未被六棱山北麓断裂中段的水平拉张作用完全吸收和调节,剩余的应变分量可能继续向NE方向传递,故与六棱山北麓断裂西段走向基本一致的六棱山北麓断裂的东段也可能具有右...     

山西大同与晋中盆地全新世活动断裂定量研究中热释光与14C测年方法应用

文章通过对山西断陷系内4条边界活动断裂带开展全新世活动定量研究中实测的67个热释光测年样品及20个14C测年样品的实例分析,讨论了在断错地貌研究和探槽全新世古地震研究中,地层测年样品帮助确定断层活动事件年代、判断探槽内古地震事件的时间跨度、古地震事件的完整性及垂直断距的不确定性等方面发挥的作用;并讨论了少量热释光样品出现年代倒置现象的原因。     

Application of River Longitudinal Profile Morphometrics to Reveal the Uplift of Lushan Mountain

The stream power model was applied to Lushan Mt. in South China in order to verify its capability of interpreting the uplift of a small block mountain. On a log-log plot, the longitudinal profiles of 9 rivers derived from a 30m DEM exhibit primary characteristics similar to those derived from a 5m DEM; however, the 5m DEM clearly reveals more minor knickpoints, and the positions of knickpoints are pinpointed more accurately. All of the studied rivers on the block mountain are in a transient state due to geological perturbations. Some of them exhibit two segments in steady state separated by a slope-break knickpoint. Such rivers generally develop in a longitudinal valley, which are less perturbed by substrate inhomogeneities. The similar heights of the slope-break knickpoints and the similar uplift rate indicated by the ksn values demonstrate an almost simultaneous headward erosion induced by the fall in base level. This modelling result is consistent with the mode of formation of this particular block mountain. Our study demonstrates that the stream power model is applicable to a small tectonically-active massif only if the channel segments are in a steady state.     

雅砻江流域河道高程剖面上的堰塞坝印记

堰塞坝会对山区河流的纵剖面产生强烈扰动,在某些情况下,堰塞坝造成的河流纵剖面变陡很容易与构造作用下基准面下降的迁移裂点混淆.然而,在何种程度下堰塞坝会影响基于地貌测量的构造分析还没有系统的研究.因此本文选取青藏高原东缘的雅砻江流域为研究对象,利用遥感影像解译,结合数字高程模型(DEM),来研究堰塞坝对河流纵剖面的影响....     

青海玉树断裂带地震落石的地震地质意义

2010年青海玉树Ms 7.1级大地震引发了一系列次生地质灾害,其中地震落石是除地震滑坡外沿断裂带及其邻侧最常见的现象。对玉树震区落石的调查发现,该区多处存在非常典型的多期地震落石分布现象,指示该区地震落石的发育与其他古地震现象类似,具有多期性和一定的原地复发性。实地调查表明,该区地震落石分布的主要特征为:多集中发育在活动断裂带附近的陡峭基岩斜坡下方,分布零散,且滚动较远,并常与古地震滑坡相伴生。初步获得的8个地震落石钙膜U系测年结果分布在距今6030±300a BP、4720±210a BP、3530±490~3560±280a BP、2010±160a BP、1090±70a BP、760±20a BP和230±20a BP年龄段,与该区古地震探槽和滑坡反映的地震事件比较吻合,进一步揭示玉树断裂带附近在全新世中晚期发生过多期可导致地表产生地震落石的事件。同时也说明,地震落石及其钙膜测年是特别值得进一步探索的潜在古地震研究方法或途径。     

Modelling of piping collapses and gully headcut landforms:Evaluating topographic variables from different types of DEM

The geomorphic studies are extremely dependent on the quality and spatial resolution of digital elevation model(DEM)data.The unique terrain characteristics of a particular landscape are derived from DEM,which are responsible for initiation and development of ephemeral gullies.As the topographic features of an area significantly influences on the erosive power of the water flow,it is an important task the extraction of terrain features from DEM to properly research gully erosion.Alongside,topography is highly correlated with other geo-environmental factors i.e.geology,climate,soil types,vegetation density and floristic composition,runoff generation,which ultimately influences on gully occurrences.Therefore,terrain morphometric attributes derived from DEM data are used in spatial prediction of gully erosion susceptibility(GES)mapping.In this study,remote sensing-Geographic information system(GIS)tech-niques coupled with machine learning(ML)methods has been used for GES mapping in the parts of Semnan province,Iran.Current research focuses on the comparison of predicted GES result by using three types of DEM i.e.Advanced Land Observation satellite(ALOS),ALOS World 3D-30 m(AW3D30)and Advanced Space borne Thermal Emission and Reflection Radiometer(ASTER)in different resolutions.For further progress of our research work,here we have used thirteen suitable geo-environmental gully erosion conditioning factors(GECFs)based on the multi-collinearity analysis.ML methods of conditional inference forests(Cforest),Cubist model and Elastic net model have been chosen for modelling GES accordingly.Variable's importance of GECFs was measured through sensitivity analysis and result show that elevation is the most important factor for occurrences of gullies in the three aforementioned ML methods(Cforest=21.4,Cubist=19.65 and Elastic net=17.08),followed by lithology and slope.Validation of the model's result was performed through area under curve(AUC)and other statistical indices.The validation result of AUC has shown that Cforest is the most appropriate model for predicting the GES assessment in three different DEMs(AUC value of Cforest in ALOS DEM is 0.994,AW3D30 DEM is 0.989 and ASTER DEM is 0.982)used in this study,followed by elastic net and cubist model.The output result of GES maps will be used by decision-makers for sustainable development of degraded land in this study area.     

Gully development in eastern Romania: a case study from Falciu Hills

The gullied systems from the Falciu Hills within the Chioara catchment (2997 ha) consist of both main types of gullies, discontinuous and large continuous ones along valley bottoms, and lots of ephemeral gullies. Several methods have been used to measure and estimate gully characteristics. Then, the gully development stages, the effect of the natural conditions, and especially the impact of land management on gullying in the Falciu Hills over the last two centuries have been defined. In addition, the role of gully erosion in triggering landslides has also been studied. Two main periods have been distinguished (until 1960 and 1961–2012) for assessing major characteristics of land degradation. The results show that total gully area in the Chioara catchment is 66.4 ha excepting for the ephemeral gullies, and areas occupied by gullies from the five study sub-catchments (2334 ha) account for two-thirds. Total length of the main gully network in the entire catchment is 33.2 km from which the five sub-catchments account for 71 %. The mean gully density of 1.11 km km⁻² supports the evidence that here gullying is the major environmental threat. Half of the gully areal growth and three-quarters of the new landslide area occurred over the 1961–2012 period. Delayed deforestation peaking during 1830–1930 and land conversion to arable use resulted in severe soil erosion, high aggradation along the non-gullied valley bottoms, and severe gullying. The average gully head retreat rate over the last two centuries from four trunk continuous gullies is 14 m year⁻¹, and the sediment yield from gullying only accounted for 54–69 % of the sediment mass produced by water erosion. The evolution of gullies is linked to major land-use changes in the study area. Despite a decreasing tendency of gullying and catchment area over the last half century, gullying still remains problematically high in East Romania.

     

基于地貌结构与汇水特征的沟谷节点提取与分析——以陕北黄土高原为例

沟谷节点是流域中线状沟谷或河网的交汇点,集中反映了沟谷的地貌结构和水文特征。有效获取并分析沟谷节点的结构与特征规律,对于系统、深入地研究流域地貌的空间形态结构、径流特征具有重要的作用。利用陕北黄土高原多地貌类型为实验区,设计并实现了基于高精度DEM的沟谷节点提取算法模型和等级标定方法,获取了实验区各级沟谷节点的数量和汇水值;运用数学模型分析法,分析了沟谷节点的数量和汇水值的分级数量关系,得到了具体的数学模拟方程;同时,运用等差分级的方式,分析了汇水累积量级差在不同地貌区的差异,初步探讨了地表形态在空间上的分异规律。     

西秦岭北缘断裂带黄香沟段晚第四纪 活动表现与滑动速率*

文章对西秦岭北缘断裂带黄香沟段的沉积建造、构造地貌等开展了野外调查与研究。冲沟位错、断裂剖面、山脊位错、线性槽地、洪积扇变形与断塞塘等详细的构造地貌分析,显示断裂带在黄香沟段晚第四纪具有较强的活动性,以左旋走滑兼有倾滑分量为特征。根据其中两条晚更新世末期以来的冲沟左旋水平位错平均值30.5±3.0m,及其¹⁴ C限定的冲沟发生位错的年龄为13480±240aB.P.,获得断裂晚第四纪的水平滑动速率为2.3±0.2mm/a。 同时,由断裂位错洪积扇形成的1.05±0.30m垂直位移量,与该期洪积扇形成的¹⁴ C年龄3690±100aB.P. ,估算了断裂晚第四纪的垂直滑动速率为0.28±0.08mm/a。     

牛首山-罗山断裂带北段柳木高断裂第四纪活动特征

牛首山-罗山断裂带是青藏高原东北缘弧形断裂系最外缘断裂带,自南向北由固原断裂、罗山东麓断裂、牛首山断裂及三关口断裂组成。通过遥感解译、野外调查及探槽揭露等方法对牛首山断裂北段柳木高断裂第四纪几何学、运动学特征进行了研究,并通过断层截切地层关系及年代学测试,限定了该断裂第四纪演化过程及全新世的地震事件。研究结果表明,柳木高断裂上新世至晚更新世自南西向北东逆冲,晚更新世至全新世左行走滑逆冲,表现为正花状构造,而全新世则发生了正倾滑运动。全新世期间,1690±30 yr BP（公元320-415）之后发生了一次古地震事件,推测柳木高断裂可能是公元876年青铜峡南6.5级地震的发震断裂。柳木高断裂第四纪早期活动特征与固原断裂、罗山东麓断裂及牛首山断裂一致,是青藏高原北东向持续扩展引起的,而全新世的正倾滑运动可能与银川地堑的伸展作用有关。      

A simple DEM assessment procedure for gully system analysis in the Lake Manyara area,northern Tanzania

Gully erosion is a major threat concerning landscape degradation in large areas along the northern Tanzanian Rift valley. It is the dominant erosion process producing large parts of the sediments that are effectively conducted into the river network. The study area is located in the Lake Manyara—Makuyuni River catchment, Arusha, northern Tanzania. During fieldwork, we measured topographic data of eight gully systems close to Makuyuni Town. The main focus of this study is to assess gully erosion dynamics using improved DEMs with original resolutions of 30 and 20 m, respectively. We assessed terrain characteristics to extract information on environmental drivers. To improve the DEM, we integrated information deduced from satellite images as well as from acquired GPS field data. Topographic indices such as Stream Power Index or Transport Capacity Index were derived from the re-interpolated DEM. To evaluate gully evolution, we assessed also the longitudinal slope profiles. Finally, the gully evolution phases of each gully were classified according to the concept proposed by Kosov et al. (Eksperimental’naya geomorfologiya, vol 3. Moscow University, Moskva, pp 113–140, 1978). The re-interpolated DEMs revealed a positive response especially for the more developed gullies. We show that the extraction of information on this spatial process scale based on “low-resolution” data is feasible with little additional fieldwork and image interpretation. In fact, areas identified as having a greater risk of gully erosion have been confirmed by observations and surveys carried out in the field.