基于加权证据权模型的丽江—小金河断裂中南段滑坡易发性评价

丽江—小金河断裂全新世活动强烈、地震频发,沿断裂带的滑坡地质灾害极为发育。以断裂带中南段两侧10 km为研究区,根据地质地理环境和滑坡发育特征,选取高程、坡度、坡向、距活动断裂距离、距河流水系距离、距道路距离、工程地质岩组、降雨量、土地利用类型以及地震动峰值加速度10个影响因子为评价指标,运用加权证据权模型,开展丽江—小金河断裂中南段滑坡易发性评价,基于自然断点法将滑坡易发程度划分为高易发、中等易发、低易发和非易发4个级别,评价结果AUC值为0.81。结果显示：(1)研究区内滑坡受坡度、断裂、水系、岩性因素的影响程度更高;(2)高易发区和中等易发区主要沿断裂带和金沙江等主要河流水系两侧分布,在玉龙县、松坪乡、大东乡等周边区域较集中;(3)西川乡处于高易发区,但目前滑坡灾害点较少,应加强关注。     

联合DBSCAN聚类采样和SVM分类的滑坡易发性评价

针对基于机器学习的滑坡易发性评价中非滑坡样本选取不规范导致的分类精度较低问题,本文提出联合基于密度的噪声应用空间聚类（Density-Based Spatial Clustering of Applications with Noise,DBSCAN）采样策略和支持向量机（Support Vector Machine,SVM）分类方法的DBSCAN-SVM滑坡易发性评价模型。首先,基于DBSCAN聚类和空间分析选取非滑坡样本;然后,将样本数据代入SVM分类模型进行训练与验证,预测并提取SVM分类中属于滑坡的概率,获得滑坡易发性;最后,以四川省绵阳市为试验区,预测滑坡易发性概率,基于滑坡易发性精度与分级结果等要素,与传统非滑坡样本采集策略的SVM滑坡易发性评价模型进行对比,并结合实际情况对DBSCAN-SVM模型评价结果进行分析。研究结果表明,相比传统SVM滑坡易发性评价模型,本文提出的DBSCAN-SVM滑坡易发性评价模型在高易发区和极高易发区中包含的滑坡样本数量较多,准确率、召回率、AUC、F1分数均得到提高,精度较高。     

基于GIS的2005年克什米尔地震区滑坡易发性区划

2005年10月8日发生的MW7.6克什米尔地震在喜马拉雅地区的巴基斯坦与印度的北部触发了数千个滑坡。这些滑坡密集分布于6个地貌—地质—人类活动环境区内。基于ASTER卫星影像和GIS技术,构建并分析了一个包含2252个滑坡的空间数据库。应用滑坡多元评估判据确定单次地震事件触发滑坡各个地震滑坡控制参数的重要性。这些控制参数包括岩性、断裂、坡度、坡向、高程、土地覆盖类型、河流与公路。结果展示了4类级别的滑坡易发区域。此外,结果还表明了岩性对滑坡的影响作用最大,尤其在岩石高度破碎区域,例如页岩、板岩、碎屑岩、石灰岩与白云岩。还有,距离断层、河流与公路较近也是滑坡发生的一个重要因素。滑坡也常常发生在坡向朝南的中海拔斜坡上。灌木林地、草原、农业用地也是滑坡易发区域,而森林覆盖的斜坡较少发育滑坡。研究区的1/3被滑坡极高易发区或高易发区所覆盖,需要开展快速的滑坡减灾措施。其余的区域为滑坡低易发区与中易发区,相对稳定。本文研究支持以下观点:(1)地震触发滑坡往往发生在地震滑坡控制参数相关的特定区域内;(2)在西喜马拉雅地区,森林砍伐与公路建设往往是同震滑坡或地震后短期内滑坡发生的重要控制因素。     

茶园沟泥石流易发性综合评价

本文基于模糊数学中多级综合评判的理论与方法,运用专家调查打分法确定各评价因子的权重,并结合茶园沟泥石流灾害的具体特点、成因和机理,选取典型的评判因子,建立二级评判模型,对茶园沟泥石流易发性进行二级模糊综合评判。     

基于迁移学习的青藏高原东北缘地震诱发滑坡易发性评估模型

通过研究,旨在提出一种迁移学习方法,以应对机器学习在缺乏历史滑坡点数据的大区域很难取得良好的评估效果的挑战。首先,通过结合10个影响因子利用随机森林算法对2013年芦山7.0级地震极震区进行预训练,得到高精度的预训练模型。随后,采用直推式迁移学习方法进行初始迁移,并利用“半监督”评估方式补充青藏高原东北缘地区的标签数值点。最后,利用归纳式迁移学习进一步训练预训练模型,得到在青藏高原东北缘地区评估更准确的地震诱发滑坡易发性评估图。此外,使用Kullback-Leibler散度计算迁移前后区域影响因子数据的相似性,并对2022年泸定6.8级地震极震区进行评估应用,验证基于迁移学习的青藏高原东北缘地震诱发滑坡易发性评估模型的准确性。研究结果可为该区域地震诱发滑坡灾害预防提供一定的参考。     

集镇地质灾害易发性分区研究——以梅州市大埔县银江镇为例

基于梅州市大埔县银江镇的地质灾害勘查资料,结合广东典型山地丘陵地区的地质环境条件,选取地质灾害点的点密度、面密度、体密度、坡度、岩土类型、断裂密度、年降雨量和人类工程活动强弱情况等8个因子,建立镇域地质灾害易发性分区的指标体系。在GIS平台上应用综合指数法,计算出833个基本评价单元（0.5 km×0.5 km）的地质灾害综合易发性指数,并据此进行了银江镇地质灾害易发性区划。研究发现：银江镇地质灾害分区以中、高易发区为主,分别占总面积的36.63%和36.67%,其中高易发区灾害点数量占到总数的74.08%。研究结果可以为合理减少银江镇的地质灾害危害性、风险性提供基础的地质依据。     

基于CF多元回归模型的地震滑坡危险性研究——以香港屯门为例

本文根据前人的研究成果以及对自1300年以来地震滑坡震例研究的基础上,选取了岩性、断裂距离、地震烈度、地形坡度、高程、水系等6个因子作为地震诱发滑坡的影响因子,并确定出各个因子在地震滑坡事件中的影响权重.通过GIS技术将滑坡确定性系数CF与回归模型相融合,建立CF值多元回归模型,以解决滑坡评价过程中影响因子的选择及量化的问题.最后,将模型应用于香港屯门地区,进行了该区的地震滑坡空间分布及稳定性初步分析.     

采坑型滑坡地质力学模式研究--以贵州省福泉滑坡为例

福泉滑坡具有顺倾上硬下软的结构特征,采用颗粒流离散元模拟采动滑坡的变形破坏全过程,研究福泉滑坡在露天开采条件下变形破坏的地质力学模式。基于颗粒流离散元程序,引入平行粘结模型,通过参数标定确定细观参数与宏观力学性质的关系,据此建立斜坡模型,模拟斜坡采动过程中的变形破坏全过程,确定该类采动滑坡形成的地质力学模式;研究滑坡滑动过程中的速度和能量变化以及堆积特征。研究表明:斜坡采动过程中,潜在滑面顺层滑移,后缘拉裂,裂纹从下往上向软弱面拓展,前缘坡脚处岩体形成锁固段,斜坡出现由前缘至后缘缘递减的蠕滑变形,随着斜坡进一步采动,锁固段发生剪切破坏,前缘坡体启动,中后部裂缝贯通—滑移,斜坡整体失稳破坏,形成牵引式采动滑坡,该类滑坡形成的地质力学模式可分为:滑移—拉裂—剪断3个阶段;对滑坡运动过程的模拟可知,采坑积水是小坝组受灾的关键转化因子。     

汶川地震滑坡危险性评价——以武都区和文县为例

利用GIS技术详细研究汶川地震在甘肃省陇南市武都区和文县触发的滑坡地质灾害的分布规律及其与地震烈度、地形坡度、断层、高程、地层岩性的相关关系,采用基于GIS的加权信息量模型的崩塌滑坡危险性评价方法,对研究区的地震滑坡危险性进行学科分析。结果表明：极高危险区在高程上主要分布在集水高程区,高度危险区主要沿白水江、白龙江等主干河流两侧极高易发区的边界向两侧扩展,轻度和极轻度危险区面积占比较小,主要分布在低烈度、活动断裂不发育、人类活动微弱的高海拔地区,另外国道G215沿极高危险性区域分布明显;利用危险性等级分区结果统计人口公里格网数据,得到武都区和文县潜在影响人口,发现研究区约78万人将受到地震滑坡灾害的潜在影响。     

Verification of landslide susceptibility mapping: a case study

A methodology is proposed for mapping susceptibility to landsliding and validating the results. Heavy rains in late 1996 and early 1997 led to a large number of landslids in the Rute sector (Córdoba, Southern Spain), where landslide susceptibility mapping had previously been carried out using a ‘matrix’ method developed with a Geographical Information System (GIS). Analysis of the distribution of the new landslides (or reactivated earlier ones) enabled the methodology to be validated by calculating association coefficients and determining the closeness of the match between subsequent field evidence and the previously defined susceptibility levels. From the data obtained, it can be concluded that the susceptibility mapping effectively explained the spatial distribution of landslides, thus providing valuable information on stability conditions over a widespread area. Copyright © 1999 John Wiley & Sons, Ltd.     

Emergency assessment of seismic landslide susceptibility： a case study of the 2008 Wenchuan earthquake affected area

The 8.0 Mw Wenchuan earthquake triggered widespread and large scale landslides in mountainous regions.An approach was used to map and assess landslide susceptibility in a given area. A numerical rating system was applied to five factors that contribute to slope instability. Factors such as lithology, topography, streams and faults have an important influence as event-controlling factors for landslide susceptibility assessment. A final map is provided to show areas of low,medium, and high landslide susceptibility. Areas identified as having high landslide susceptibility were located in the central,northeastern, and far south regions of the study area. The assessment results will help decision makers to select safe sites for emergency placement of refuges and plan for future reconstruction. The maps may also be used as a basis for landslide risk management in the study area.     

Dependence of air pollution on meteorological conditions based on magnetic susceptibility measurements: a case study from Warsaw

This study reports systematic analysis of air pollution concentration by particulate matter (PM) in relation to annual changes of metrological conditions. The concentration of PM collected on filters was evaluated by magnetic properties. Long series of filters collected during 1977, 1980, 1981 and 1985 in Warsaw have been used for measurement. Such long time series allowed a better determination of correlation between seasonal susceptibility changes and meteorological conditions and to verify the repeatability of annual behavior. The magnetic susceptibility normalized by mass (??) has been used as a proxy of pollution. Monthly variations of ?? (??_m) demonstrated slow and small seasonal changes disturbed by quick, high peaks. The filters with high susceptibilities contain a mixture of magnetic single and multidomain grains which is characteristic for anthropogenic pollution, with the frequency-dependent susceptibility ??_fd being less than 4%. The low susceptibility samples are characterized by admixture of small amount of pseudo-single domain (PSD) and possible small amount of superparamagnetic (SP) grains. Detailed analysis of reduced mean monthly susceptibility ??_R revealed that temperature and absolute humidity correlate positively in cold period of year and negatively in warm months. The linear correlation coefficients range from 0.7 to 0.9 and from 0.3 to 0.4 for negative and positive linear correlation, respectively. The dispersion of pollutants in a city depends on the way of ventilation. The big cities like Warsaw are urban heat islands which act the most effective way for the warm period and for the cold time. The correlation of ??_R with absolute humidity is similar to that for temperature but for different reasons. The presence of big amount of water vapor particles in the atmosphere can favor the adhesion of smaller ferromagnetic grains to their surface which can accelerate the process of falling down of such agglomerates. Such a process can take place during wintertime. We do not observe clear correlation between ??_R and precipitation.     

Landslide stability analysis based on random-fuzzy reliability: taking Liangshuijing landslide as a case

A large number of reservoir landslides will be impacted under the action of cyclical water level change in Three Gorges Reservoir, therefore its stability analysis and evaluation are important. And various kinds of influencing factors should be considered when landslide stability is analyzed. Taking Liangshuijing landslide as a case, considering the uncertain factors in the landslide stability analysis process, the landslide random-fuzzy reliability is analyzed in the paper, based on the sliding soil shear strength parameters testing and groundwater monitoring data. The results show that the landslide random-fuzzy reliability is the smallest at the process of high water level slowly dropping to low water level, and the landslide is basically at a steady state, which is consistent with landslide body actual deformation. Taking into account the uncertainty of groundwater level in a landslide body is equivalent to taking into account the changes of occurrence conditions in landslide rock and soil. Taking these factors into account is more in line with the actual when compared with only considering shear strength parameters random properties.     

GIS‐based regional landslide susceptibility mapping: a case study in southern California

Landslides threaten lives and property throughout the United States, causing in excess of $2 billion in damages and 25–50 deaths annually. In regions subjected to urban expansion caused by population growth and/or increased storm intensities caused by changing climate patterns, the economic and society costs of landslides will continue to rise. Using a geographic information system (GIS), this paper develops and implements a multivariate statistical approach for mapping landslide susceptibility. The presented susceptibility maps are intended to help in the design of hazard mitigation and land development policies at regional scales. The paper presents (a) a GIS‐based multivariate statistical approach for mapping landslide susceptibility, (b) several dimensionless landslide susceptibility indexes developed to quantify and weight the influence of individual categories for given potential risk factors on landslides and (c) a case study in southern California, which uses 11 111 seismic landslide scars collected from previous efforts and 5389 landslide scars newly digitized from local geologic maps. In the case study, seven potential risk factors were selected to map landslide susceptibility. Ground slope and event precipitation were the most important factors, followed by land cover, surface curvature, proximity to fault, elevation and proximity to coastline. The developed landslide susceptibility maps show that areas classified as having high or very high susceptibilities contained 71% of the digitized landslide scars and 90% of the seismic landslide scars while only occupying 26% of the total study area. These areas mostly have ground slopes higher than 46% and 2‐year, 6‐hour precipitation greater than 51 mm. Only 12% of digitized landslides and less than 1% of recorded seismic landslides were located in areas classified as low or very low susceptibility, while occupying 42% of the total study region. These areas mostly have slopes less than 27% and 2‐year, 6‐hour precipitation less than 41 mm. Copyright © 2007 John Wiley & Sons, Ltd.     

甘肃永登湿陷性新近堆积黄土的微观结构分析

甘肃永登县树屏村某工程场地土为第四纪新近堆积黄土,其工程性质较为特殊,具有较大的湿陷性,但在天然湿度下震陷性却很小。本文利用扫描显微镜对其微结构图象进行分析,同时结合土工试验结果,揭示了导致其特殊工程性质的微观机理。最后提出了在工程施工中应注意的问题。     

Dam risk assessment based on univariate versus bivariate statistical approaches: a case study for Argentina

Abstract

Considering floods as multivariate events allows a better statistical representation of their complexity. In this work the relevance of multivariate analysis of floods for designing or assessing the safety of hydraulic structures is discussed. A flood event is characterized by its peak flow and volume. The dependence between the variables is modelled with a copula. One thousand random pairs of variables are transformed to hydrographs, applying the Beta distribution function. Synthetic floods are routed through a reservoir to assess the risk of overtopping a dam. The resulting maximum water levels are compared to estimations considering the peak flow and volume separately. The analysis is performed using daily flows observed in the River Agrio in Neuquén Province, Argentina, a catchment area of 7300 km². The bivariate approach results in higher maximum water level values. Therefore the multivariate approach should be preferred for the estimation of design variables.

Editor D. Koutsoyiannis; Associate editor S. Grimaldi     

Simulating and mapping the risk of surge floods in multiple typhoon scenarios: a case study of Yuhuan County,Zhejiang Province,China

We propose a scenario-based method for simulating and mapping the risk of surge floods for use by local authorities concerned with public safety and urban planning in coastal areas. Focusing on the triad of hazard, vulnerability and adaptation capability, we estimate the comprehensive risk and display its spatial distribution using the raster calculation tool in ArcGIS. The detailed methodology is introduced via a case study of Yuhuan, an island county in Zhejiang Province, China, which is frequently affected by typhoon storm surges. First, we designed 24 typhoon scenarios and modeled the flood process in each scenario using the hydrodynamic module of MIKE 21. Second, flood depth and area were used for hazard assessment; an authorized indicator system of land use categories and a survey of emergency shelters were used for vulnerability and adaptation capability assessment, respectively; and a quantified model was used for assessment of the comprehensive risk. Lastly, we used the GIS raster calculation tool for mapping the risk of storm surges in multiple typhoon scenarios. Our principal findings are as follows: (1) Seawalls are more likely to be overtopped or destroyed by more severe storm surges with increasing typhoon intensity. (2) Most of the residential areas with inadequate emergency shelters are highly vulnerable to flood events. (3) As projected in the risk mapping, if an exceptional typhoon with a central pressure of 915 or 925 hPa made a landfall in Yuhuan, a wide range of areas would be flooded and at high risk. (4) Determining optimal strategies based on identification of risk-inducing factors is the most effective way of promoting safe and sustainable development in coastal cities.     

significance of high-resolution loess stratification based on grain size and magnetic susceptibility analysis to paleo-earthquake study: a case study of dongyugou loess section,at hongtong,shanxi province

As an important technology to paleoseismologic research, trenching has been used to identify paleo-earthquakes recorded in strata, combined with dating technology. However, there have been some bigger uncertainties and limitations. For instance, subtle strata in loess sediment cannot be interpreted only by naked-eye, which seriously affects identifying paleo-earthquake horizon and time. Therefore, how to improve the accuracy and reduce the uncertainty of paleo-earthquake identification is the important problem we are currently facing. Dongyugou loess section, located in the northeastern corner of Linfen Basin, Shanxi Province, cuts across the Huoshan piedmont fault. The section exposes not only the well-developed loess sequence, but also several obvious faulting events. Thus, this loess section is a better site to make a high resolution study to improve the accuracy and reduce the uncertainty of paleo-earthquake identification. Based on the high-resolution grain size and magnetic susceptibility analysis, and associated with visual interpretation by naked-eye, we made a high-resolution stratification of Dongyugou loess section, including high-resolution thickness of each stratum and its upper and bottom boundaries. Based on the high-resolution stratification and their comparison between two fault walls, we identified three earthquake events, which occurred after formation of u5-7, u4 and u2, corresponding to their stratification depth of 7.1m, 4.7m and 2.9m in hanging wall. Based on results of OSL dating and average sedimentation rate of hanging wall, we estimated that the three events occurred around 45.8ka(between (48.1±1.5)～(43.2±2.5)ka), 32.8ka(between (35.0±2.4)～(30.6±1.3)ka) and 23.3ka(between (26.4±0.8)～(20.9±0.7)ka). According to the thickness difference of three loess-paleosol sedimentary cycles between two fault walls, we calculated the coseismic vertical displacements of the three events as 0.5m, 0.4 and 1.3m, respectively. Compared with other segments of the Huoshan piedmont fault zone, we found the southernmost segment is the weakest, with longer recurrence interval of about 11ka and lower vertical slip rate of 0.048mm/a. The high-accuracy grain size and magnetic susceptibility analysis offers an effective method for reducing the uncertainties of the paleo-earthquake research in loess area.     

汶川地震甘肃省文县地震地质灾害遥感分析

2008年汶川地震诱发了大量的次生山地灾害.本文以多源、多时相的遥感影像(TM、ASTER、SPOT)作为信息源,基于地学知识,采用图像增强、人机交互的方式对甘肃省文县地区汶川地震引发的次生山地灾害进行解译.以ArcGIS软件为处理平台,运用空间分析技术,将解译结果与海拔高度、坡度、植被覆盖度和地震烈度进行空间分析,获得了研究区次生山地灾害的分布规律,其特点为:文县境内的次生山地灾害主要分布在20°～60°的边坡;多发生在1 000～2 500m的海拔高程范围内;主要分布在地震烈度Ⅶ度及以上区域.