美姑河流域地质构造对大型滑坡孕育的控制作用

地质构造及其活动特征与滑坡灾害的关系是工程地质研究中的热点问题。文章在川西南大凉山区美姑河流域地质构造资料分析和大型古滑坡精细化调查的基础上,以流域内的典型古滑坡为研究对象,结合该地区地质构造的几何学、变形学、运动学和活动性特征,深入剖析了沉积构造、断裂构造、褶皱构造和节理构造等不同的地质构造类型对大型古滑坡的孕育的控制作用,认为地质构造对大型滑坡的控制主要表现在:(1)断层破碎带、节理密集带等不连续结构面控制了滑坡发育的边界,(2)断层破碎带、褶皱弯滑作用的滑动层面、沉积结构软弱夹层等孕育滑带的形成,(3)节理构造形成的裂隙构成地下水储集和运移的通道,促进滑坡的孕育和大型滑坡的发生,(4)活动断裂制约着滑坡地貌发展演化,诱发断裂活动的地震导致了大型滑坡失稳。建议在美姑河流域的滑坡灾害防治方面应加强不同尺度,尤其是中小尺度活动构造与滑坡发育演化研究。     

甘肃中部第四纪以来滑坡发育期次划分及特征

通过滑坡形成期次的划分，确定区域滑坡灾害旋回周期，对制定区域滑坡防治对策具有重要意义。借助已较为成熟的地貌发育史、气候史和新构造运动演化史，再应用^14C和热释光等绝对测年法，将陇中地区的滑坡划分为古滑坡（Q3^1）、老滑坡（Q4^1)、新滑坡(Q4^2)和现代滑坡(Q4^3)四个活跃期。     

青藏高原东缘深切河谷区古滑坡:判识、特征、时代与演化

青藏高原东缘是全球古滑坡最发育的地区之一。基于大量地面调查、遥感解译和年龄测试资料,总结了青藏高原东缘深切河谷区古滑坡的判识方法、主要发育特征、形成时代和分布规律。结果表明,古滑坡具有规模巨大、高位起动、物质组成和结构复杂等特征,其空间分布与地形地貌、岩性组合和活动构造等因素关系密切。古滑坡在区域上受气候变化影响较明显,一般形成于河流强烈下切阶段,与河流阶地具有较好的对应关系,多数已发现的古滑坡与T₂阶地时代相当,时间跨度为40~10 ka,集中分布于30~20 ka。构造活动和地震造成古滑坡在不同区段的分布具有差异性,一般在活动断裂带附近密集发育,现今发现的古滑坡多为这种成因。这些认识对于科学认知古滑坡的形成演化过程和未来巨灾风险预测具有重要的指导作用。     

地衣测年及其在第四纪年代学上的应用

地衣测年是20世纪50年代提出并逐渐发展起来的一种测年方法,已被应用于冰川地貌、古滑坡、古地震等地质事件的测年中,尤其在侵蚀速率较大、沉积物难以保存的地区具有独特的优势。虽然地衣测年仍不完善、在具体应用中存在一些问题、国内外学者对该方法也有争议,但随着研究的深入以及相关问题的解决,其对于全新世以来地质事件的测年具有广泛的应用前景。本文整理了地衣测年的发展历史和存在问题,并展望了地衣测年的未来发展方向。     

岷江上游河流阶地发育特征及与古滑坡关系初步分析

河流阶地形成演化及其对滑坡的控制是近年来古滑坡研究的热点问题。笔者在对岷江上游河流阶地和古滑坡实地调查测试的基础上,对岷江上游河流阶地的级序、拔河高度、成因类型等进行了分析,绘制了阶地高程位相图和年龄位相图,并结合阶地和古滑坡年代,讨论了阶地与古滑坡的发育关系等。主要取得了以下认识:1)岷江上游的河流阶地具有分段性,成因主要为气候多期次波动与构造活动共同作用,古滑坡及堰塞湖是影响高山峡谷区河流阶地发育的重要因素;2)叠溪-茂县段在20~30 ka B.P.发生了多处大型古滑坡,其中20 ka B.P.的古滑坡可能主要是气候波动引发,30 ka B.P.发生的古滑坡可能主要受控于构造活动(地震);3)岷江上游大量分布的古滑坡堆积体与阶地发育的叠置关系有待进一步理清,开展该地区的河流阶地级序研究要充分考虑古滑坡和堰塞湖的影响.     

特约主编致读者

特约主编致读者 崔鹏刘维明王昊 21世纪以来,在气候变化、构造活动与人类活动的综合作用下,自然灾害强度和风险明显增大,严重危害人类社会的发展,防灾减灾已成为全人类共同面临的巨大挑战和亟须解决的重大课题。特别是巨型灾害,往往造成严重的生命财产损失,甚至对区域或全国性社会经济系统造成严重冲击。巨灾突发性强,发生频率低,观测数据和历史记录稀缺,形成机理与风险演化规律研究难度大,目前科学认识难以满足巨灾的防灾需求。从地质历史记录中捕捉与重建巨型古灾害事件,分析其时空分布特点,认识其发育机制和风险演化规律,可以有效弥补现有观测数据缺乏的不足,为巨灾风险防范提供科学依据和理论支持。 目前,古灾害研究在国际上已经取得了长足的进展,发现了众多超出已有认知的极端事件,比如洪峰达到107 m3/s造成全球气候突变的北美大洪水。这些极端事件的发现极大促进了对地球表层动力过程灾害效应的认识。中国地学界非常关注古灾害研究,形成了古灾害研究的科学群体,在该领域取得了一系列成果,也在防灾减灾的实践中发挥了巨大作用。 为了集中体现我国古灾害的研究成果,《地学前缘》编辑部委托我们邀请从事古灾害研究的专家撰文,汇编成《古灾害：沉积、地貌与年代》专辑,主要介绍我国不同灾种古灾害的沉积和地貌特征、测年方法、区域分布和发育规律等。本专辑共收录18篇文章,分为测年方法、古灾害链、古滑坡、古洪水、古地震和古海洋灾害6个栏目。 确定古灾害事件的年代是重建灾害演化过程的关键。测年方法栏目共收录2篇文章:赖忠平等综述了灾变过程的年代学研究,围绕不同灾害过程的沉积体系介绍野外采样策略和对应的测年方法;灾变沉积测年的不确定性是制约古灾害事件重建的重要因素,白世彪等提出了提高古滑坡定年精度的途径。巨型灾害具有典型的链生效应。古灾害链栏目共5篇文章,王萍、殷志强和刘维明等分析了雅鲁藏布江中下游、黄河上游以及雅砻江古堰塞事件的发育特征和分布规律以及地貌效应等,范宣梅和陈剑等分别介绍了岷江上游叠溪和金沙江上游特米巨型古堰塞湖。滑坡是山区最为频发的灾害。古滑坡栏目共收录3篇文章,张永双等以青藏高原东缘为例介绍了深切河谷区古滑坡的判识、特征和定年,王玉峰和黄小龙等分别介绍了高速远程滑坡沉积动力学特征和程海断裂的古滑坡分布规律。洪水是对人类影响最广泛的灾害。古洪水栏目共收录4篇文章,王昊和郭永强等的综述文章分别介绍了高能（溃决）洪水的沉积特征和高山峡谷区古洪水的重建方法,朱诚等系统研究了成都平原一处典型文化遗址古洪水沉积的时代和成因,苏怀等以金沙江2018年白格洪水为例总结了现代溃决洪水的沉积特征。地震破坏力极大,往往造成毁灭性灾害。古地震栏目共收录2篇文章,刘静等介绍了古地震学的研究历史、前沿和发展趋势,李德文等总结了湖泊沉积古地震研究的主要进展、存在的问题和解决途径。我国海洋开发对古海洋研究提出了新的需求。古海洋灾害栏目共收录2篇文章：杨文卿等重建了南海1076年的古海啸事件,分析了其对沿海岛屿的社会经济影响;孙启良等分析了南海北部海底滑坡的特征,进行了灾害评估,指出了海底滑坡的成因机制和潜在海底滑坡的识别方法。 最后,希望更多的科学家能够关注古灾害研究,并把古灾害研究与现代灾害研究紧密结合,不断深化灾害形成与风险演化机理探索,服务巨灾风险防范。 值此古灾害专辑付梓之际,谨向各位作者和评审专家为本专辑做出的科学贡献,以及《地学前缘》编辑部的精心把关表示衷心感谢！ 文中全球尺度的海底地形数据由GEBCO（www.gebco.net）提供,在此一并致谢。     

古滑坡复活问题研究进展与展望

古滑坡是斜坡长期复杂演化过程的产物,物质组成复杂、岩土力学性质特殊,具有极强的隐蔽性和扰动敏感性。随着人类工程活动不断加剧和极端天气频繁出现,国内外发生了大量古滑坡复活导致的交通、水电工程等重要设施毁坏和人员伤亡等灾难性事件,灾害风险日益严峻。通过梳理国内外古滑坡研究现状,总结了古滑坡区域发育规律及古滑坡判识研究、古滑坡体和古滑带的物理力学性质研究、古滑坡的复活机理研究、古滑坡复活过程及其模拟分析、古滑坡复活的早期识别研究等方面的主要进展。结合当前防灾减灾需求,提出古滑坡复活问题研究的3个关键科学问题是:(1)古滑坡自动化判识方法和准则;(2)基于新强度理论的古滑坡复活起滑机理;(3)古滑坡复活的早期识别模型和评价方法。破解这些关键科学问题,将为重大工程规划和防灾减灾提供新的理论和技术支撑。     

基于InSAR形变监测的四川甲居古滑坡变形特征

位于四川省丹巴县聂呷乡甲居村的甲居古滑坡主要由甲居滑坡(H01)、聂呷坪滑坡(H02)、小巴旺村滑坡(H03)、聂拉村滑坡(H04)和山顶滑坡(H05)等5个次级滑体组成.受区域构造、强降雨、河流侵蚀、地层岩性等因素影响,甲居古滑坡次级滑体持续发生蠕滑变形,对位于滑体上的村庄、道路和前缘大金河等具有较大危害,2020年遭受50年一遇的强降雨后,古滑坡变形速率有进一步增大的趋势.采用SBAS-InSAR技术,结合遥感解译和现场调查,获取了甲居古滑坡2018年6月至2021年8月的地表变形特征,通过二维形变速率转换获取了甲居古滑坡沿斜坡向(slope)和垂直向(vertical)的形变速率.研究认为,甲居古滑坡沿雷达视线方向(V_LOS)形变速率最大达-179 mm/a,沿斜坡方向的形变速率(V_s)最大为-211 mm/a,沿垂直方向的变形速率(V_v)最大为-67 mm/a.甲居滑坡的北侧区域、聂拉村滑坡的南侧区域和山顶滑坡后缘变形较大,总体上位于强变形-极强变形区.甲居古滑坡的变形机制具有一定差异,其中甲居滑坡以牵引式变形为主,聂拉村滑坡以推挤式变形为主.由于古滑坡地质构造复杂、新构造活动强烈,在强降雨和河流侵蚀作用下极易导致滑坡蠕滑速率加快并进一步失稳,形成堵江溃坝等灾害.建议加强次级滑体的地表变形监测,为流域性地质安全风险防灾减灾提供技术支撑和科学依据.      

金沙江上游特米古滑坡堰塞湖形成与溃决时间讨论

开展古滑坡堰塞湖形成演化过程研究,可以揭示古灾害地质环境效应,重建区域构造历史活动序列和古气候演变特征.特米古滑坡发育于金沙江上游巴塘段,滑坡堆积地貌和堰塞湖相沉积物保存较好,是研究区内古地质环境的良好载体.在遥感解译、无人机测绘、现场调查和地质测年的基础上,结合前人研究成果,分析探讨了特米古滑坡发育特征、堰塞湖形成时...     

黄河上游特大型滑坡群发特性的年代学研究

本次研究通过对黄河上游10处古滑坡采用OSL和~(14)C两种方法测年,总结归纳了6种间接取样测年的思路,即①滑坡体上覆黄土底部、②滑坡体下伏阶地黄土顶部、③滑体内部高温剪切结构面、④堰塞湖湖相层底部、⑤错落式滑坡流水相物质底部和⑥滑坡下伏物质顶部有机碳。通过分析研究发现区内特大型滑坡具有明显的群发分期特性,分别为5万年左右、3万年左右、1.O~0.8万年左右和0.5万年左右。     

Use of landslides for paleoseismic analysis

In many environments, landslides preserved in the geologic record can be analyzed to determine the likelihood of seismic triggering. If evidence indicates that a seismic origin is likely for a landslide or group of landslides, and if the landslides can be dated, then a paleo-earthquake can be inferred, and some of its characteristics can be estimated. Such paleoseismic landslide studies thus can help reconstruct the seismic history of a site or region. In regions that contain multiple seismic sources and in regions where surface faulting is absent, paleoseismic ground-failure studies are valuable tools in hazard and risk studies that are more concerned with shaking hazards than with interpretation of the movement histories of individual faults. Paleoseismic landslide analysis involves three steps: (1) identifying a feature as a landslide, (2) dating the landslide, and (3) showing that the landslide was triggered by earthquake shaking. This paper addresses each of these steps and discusses methods for interpreting the results of such studies by reviewing the current state of knowledge of paleoseismic landslide analysis.     

黄河上游龙羊峡至积石峡段巨型滑坡OSL测年

通过对青藏高原东部黄河上游龙羊峡—积石峡段10个特大型古滑坡的地质结构、地层岩性的分析,结合各滑坡特征,在特定部位进行采样,归纳整理出滑坡光释光（OSL）测年样品的5种采样方法。选取11个样品应用OSL测年方法,得到各滑坡的年龄数据,分析各样品的可靠性,并探讨其构造时间、气候变化与滑坡群发性之间的关系。研究表明,由于样品来源广泛,实验方法高效准确,OSL方法可成功地应用于滑坡年龄测定,为滑坡研究提供可靠的地质依据。研究区特大型群发性滑坡和初步划分为4期分别为130~110ka、50~30ka、12~9ka和5~3ka,并解释了各期滑坡群发的主要触发因素。     

树轮地貌学重建滑坡事件研究进展

树轮地貌学以其定年准确、分辨率高和时间跨度长等特点在地表过程的研究中具有极其重要的作用。树木年轮可以作为一个可靠的工具来获得滑坡过去活动的历史证据,进而解释现在正在发生的并窥探滑坡的变形信息。本文对国内外树轮地貌学方法在滑坡事件研究中的现状和取得的成果进行总结,重点阐释了树轮地貌学的原理和树轮地貌学重建滑坡活动迹象与时空分布的研究进展,并讨论了该方法存在的不足,展望了我国利用树轮地貌学开展滑坡事件研究的前景。     

Tephrochronologic Constraints on Temporal Distribution of Large Landslides in Northwest Argentina

Two morphologic settings in the northwestern Argentine prone to giant mountain-front collapse-deeply incised narrow valleys and steep range fronts bordering broad piedmonts-were analyzed through detailed investigations of fossil landslides and related fluvio-lacustrine sediments. Nine different rhyodactic tephra layers were defined by geochemical fingerprinting of glass, morphology of pumice, stratigraphic relationships, and mineralogy. The age of three tephra could be determined either directly by 40Ar/39Ar dating or relatively by 14C dating of associated sediments: Paranilla Ash (723+/-89 ka), Quebrada del Tonco Ash ( approximately 30 ka), and Alemanía Ash ( approximately 3.7 ka). These units permit correlation of several spatially separate landslide deposits. Landslide deposits in narrow valleys were generated in the late Pleistocene between 40 and 25 ka and in the Holocene since ca. 5 ka and correspond to periods characterized by increased humidity in subtropical South America. In contrast, the age of large landslides in piedmont regions is significantly greater but more difficult to define by tephrochronology. However, selected deposits from this second environment have cosmogenic nuclide exposure ages of 140-400 ka. Because of the large distance of the collapsed mountain fronts from eroding streams and because of important Quaternary displacement along the mountain-bounding faults, we suggest that strong, low-frequency seismic activity is the most likely trigger mechanism for most of the landslides in this environment.     

Do landslides follow landslides? Insights in path dependency from a multi-temporal landslide inventory

Landslides are a major category of natural disasters, causing loss of lives, livelihoods and property. The critical roles played by triggering (such as extreme rainfall and earthquakes), and intrinsic factors (such as slope steepness, soil properties and lithology) have previously successfully been recognized and quantified using a variety of qualitative, quantitative and hybrid methods in a wide range of study sites. However, available data typically do not allow to investigate the effect that earlier landslides have on intrinsic factors and hence on follow-up landslides. Therefore, existing methods cannot account for the potentially complex susceptibility changes caused by landslide events. In this study, we used a substantially different alternative approach to shed light on the potential effect of earlier landslides using a multi-temporal dataset of landslide occurrence containing 17 time slices. Spatial overlap and the time interval between landslides play key roles in our work. We quantified the degree to which landslides preferentially occur in locations where landslides occurred previously, how long such an effect is noticeable, and how landslides are spatially associated over time. We also investigated whether overlap with previous landslides causes differences in landslide geometric properties. We found that overlap among landslides demonstrates a clear legacy effect (path dependency) that has influence on the landslide affected area. Landslides appear to cause greater susceptibility for follow-up landslides over a period of about 10  years. Follow-up landslides are on average larger and rounder than landslides that do not follow earlier slides. The effect of earlier landslides on follow-up landslides has implications for understanding of the landslides evolution and the assessment of landslide susceptibility.     

临夏盆地巴谢河流域晚更新世以来滑坡发育历史重建

晚更新世以来,特别是全新世以来,黄土高原西北部发育了多期次的滑坡事件。临夏盆地巴谢河流域较好地保留了多期次滑坡的遗存,有研究历史滑坡发育规律的良好素材。文章通过详细的野外调查,初步厘清了滑坡空间分布及新老滑坡相互叠置关系,总结得到本地区滑坡的四种发展类型:压裂型深层黄土-泥岩滑坡、滑移型深层黄土-泥岩滑坡、蠕变型中浅层黄土-泥岩滑坡和塌滑型黄土滑坡。不同时期发育的滑坡在野外呈现明显不同的特征:发育于晚更新世的古滑坡有圈椅状的地形和高陡的后缘陡壁,滑坡堆积体已固结,堆积体表面冲沟发育;发育于全新世早期的老滑坡除了具有圈椅状地形和高陡后壁外,堆积体较为松散,堆积平台形态较为完整;发育于全新世晚期的新滑坡则保留了更多的滑坡特征,可见滑坡后缘和侧缘裂缝。巴谢河流域滑坡大多有多次滑动的迹象,不同期次的滑坡相互重叠,在同一范围发生多次滑动,形成多级滑坡堆积平台。滑坡埋压动植物、滑坡洼地短期水体沉积物等有着明显的滑坡指示意义。通过采集此类样品,利用14C和光释光等测年手段,获取了本地区一系列滑坡事件的年龄。对测年数据进行统计分析,得到巴谢河流域晚更新世以来的五个滑坡高发时段,分别为100~63 kaBP、45.2~41.5 kaBP、33.3~28.2 kaBP、22.5~15.2 kaBP和10.4~0.2 kaBP。以上滑坡高发时段的推断将为认识去环境变迁提供证据。     

湖南五强溪库区老滑坡复活现状、成因浅析与防治对策

山体滑坡是湖南五强溪库区发生最频繁,损失最大的自然灾害之一,本文以沅陵县舒溪口上排滑坡和落坪集镇滑坡为例,阐述了湖南五强溪库区老滑坡近期复活变形特征,分析了老滑坡复活变形成因,并提出了加强预测预报、规范人为活动和如何防治的对策。     

On evaluating the stability of the Baiyian ancient landslide in the Three Gorges Reservoir area,Yangtze River: a geological history analysis

Numerous landslides have occurred during the construction of the Three Gorges Reservoir of the Yangtze River. Although the underlying causal factor of these landslides was heavy rainfall, the construction process was the trigger of some of them. We report here a systematic study aimed at reconstructing the geological history of an ancient landslide and, based on our results, an evaluation of the role of the history on current landslide stability. Data from detailed field surveys and the studies on geological dating revealed that the Baiyian landslide was composed of five structural parts of different geological ages, such as a sliding belt, disturbed rocks, ancient colluvium, alluvium of the Yangtze River and slope wash. The succession of ancient climates, terraces and tectonic processes in the study area were examined from 300 ka ago. The evolutionary history of the Baiyian ancient landslide can be divided into five distinct stages: development, occurrence, deposition, collapse and disintegration. Some parts of the ancient landslide are currently prone to instability due to the combination effects of heavy rainfall and construction of the reservoir.     

A comparison of logistic regression-based models of susceptibility to landslides in western Colorado,USA

The Paonia-McClure Pass area of Colorado has been recognized as a region highly susceptible to mass movement. Because of the dynamic nature of this landscape, accurate methods are needed to predict susceptibility to movement of these slopes. The area was evaluated by coupling a geographic information system (GIS) with logistic regression methods to assess susceptibility to landslides. We mapped 735 shallow landslides in the area. Seventeen factors, as predictor variables of landslides, were mapped from aerial photographs, available public data archives, ETM + satellite data, published literature, and frequent field surveys. A logistic regression model was run using landslides as the dependent factor and landslide-causing factors as independent factors (covariates). Landslide data were sampled from the landslide masses, landslide scarps, center of mass of the landslides, and center of scarp of the landslides, and an equal amount of data were collected from areas void of discernible mass movement. Models of susceptibility to landslides for each sampling technique were developed first. Second, landslides were classified as debris flows, debris slides, rock slides, and soil slides and then models of susceptibility to landslides were created for each type of landslide. The prediction accuracies of each model were compared using the Receiver Operating Characteristic (ROC) curve technique. The model, using samples from landslide scarps, has the highest prediction accuracy (85 %), and the model, using samples from landslide mass centers, has the lowest prediction accuracy (83 %) among the models developed from the four techniques of data sampling. Likewise, the model developed for debris slides has the highest prediction accuracy (92 %), and the model developed for soil slides has the lowest prediction accuracy (83 %) among the four types of landslides. Furthermore, prediction from a model developed by combining the four models of the four types of landslides (86 %) is better than the prediction from a model developed by using all landslides together (85 %).     

岷江上游槽谷曲流段大型古滑坡成因与复活性分析——以松潘县元坝子古滑坡为例

岷江上游靠近分水岭部位的槽谷曲流河段,由于地壳抬升缓慢,河谷宽、岸坡缓,降雨量相对偏少,通常被认为发生大型滑坡的可能性较小。但通过笔者近年来的调查发现,在岷江上游红桥关至西宁关的槽谷曲流段两岸大型滑坡密集发育,且大多具有地震滑坡的特征,同时个别滑坡受后期江水冲刷、工程开挖等因素影响复活。文章选取其中较为典型的元坝子滑坡为例进行解剖,元坝子滑坡位于岷江曲流凹岸,长780 m,宽480 m,体积293×104 m3。通过地质分析、测年鉴定和数值模拟,认为该滑坡是历史地震引发的大型岩质古滑坡,其发展经历了斜坡裂缝、地震滑坡、河流下切和前缘复活等阶段。稳定性计算结果显示,目前滑坡整体天然工况下稳定性好,极端暴雨工况下欠稳定,受江水冲刷、降雨、融雪等因素影响,出现局部变形复活。建议应加强滑坡变形监测,避免整体滑动造成堵江、威胁成兰铁路安全。