Large-scale mass wasting in ancient volcanic materials

Giant landslides are significant hazards associated with many active volcanic edifices. We describe a similar feature on ancient (>4 Ma) volcanic deposits subject to active tectonism. The landslide is approximately 3 km long by 1 km wide, with an estimated depth of 400 m. Side margins are straight and parallel, mimicking regional structure; narrow valleys incised down these margins provide low-strength side-release surfaces. Between these is a giant slump consisting of at least four, largely intact, discrete blocks that have moved down-dip a distance of >500 m. A series of flows with areal extents ranging from 0.01 to 0.5 km² extends from the front of the failure. The materials represent an eroded sequence of andesite flows on the flanks of a stratovolcano. These have undergone two phases of hydrothermal alteration, and are deeply weathered to low-density (1040±80 kg m⁻³) silt (59%) and clay (35%) materials with strength properties typical of weathered silts (c=26±3 kN m⁻²; φ=42±8°). The size and location of this landslide preclude detailed geotechnical investigation of the failure. The worth of numerical stability analysis as an alternative technique in assessing the nature of the failure and hence the risk it poses to nearby communities is investigated. Sensitivity analysis identified likely conditions under which initial failure may have occurred: analyses for sensitivity to strength and earthquake acceleration needed conversion to critical combinations (F=1.0) of water table and strength/acceleration to remove the overriding influence of water table fluctuations. Failure was likely initiated either by a high water table level (83-84%), or some combination of intensity VII-IX earthquake waves together with water table heights of 40-80%. A general hazard assessment indicates that the risk associated with creep and catastrophic failure of the main mass is small, whereas the risk from flow failures near the toe of the landslide may be high. Important parameters (hydrological regime, flow failure morphology, age of initiation, and rates of movement) requiring closer investigation are identified. Development of a model is crucial to assessing the hazard associated with a feature such as that described here. With limited resources, a detailed stability analysis is a powerful tool as an initial stage in hazard analysis.     

Seismic evaluation of existing nuclear facility using ambient vibration test to characterize dynamic behavior of the structure and microtremor measurements to characterize the soil: a case study

The methods used for a building seismic hazard evaluation are presented with the associated results. The goals of the study are (1) to check the soil nature and the existence or not of a possible site effect around the installation and (2) to characterize the dynamic behavior of the building using ambient vibration records.

The results of the soil study with the Nakamura method are very difficult to interpret because they are not stable in space and time. The spectral ratios method has been used with regional earthquake records. The results of the application of this method allowed us to conclude that the installation was free of site effect.

The ambient vibration measurements on the building brought the conclusion to determine the first and second modes of the structure. These results have been used to calibrate numerical model. The modal shapes in plan (high roof) and in elevation (main column) have been evaluated. The damping of the building has been computed using ambient vibration records.     

Evaluating Earthquake-Triggered Landslide Hazard at the Basin Scale Through Gis in the Upper Sele River Valley

To evaluate techniques for assessing earthquake-triggeredlandslide hazard in the Southern Apennines (Italy), a GIS-based analysis was used to modelseismically induced slope deformations. Geological, geotechnical, geomorphological and seismologicaldata were integrated into a standard earthquake slope stability model. The model assessed thelandslide potential that existed during the 1980 Irpinian earthquake in the Upper Sele river Valley.The standard Newmark displacement analysis, widely used for predicting the location of shallowunstable slopes, does not take into account errors and/or uncertainties in the input parameters.Therefore, a probabilistic Newmark displacement analysis technique has been used. Probabilistictechniques allow, e.g., an estimation of the probability that a slope will exceed a certain criticalvalue of Newmark displacement. In our probabilistic method, a Monte-Carlo based simulation modelis used in conjunction with a GIS. The random variability of geotechnical data is modelled by probabilitydensity functions (pdfs), while for the seismic input three different regression laws wereconsidered. Input probability distributions are sampled and the resulting values input into empiricalrelations for estimating Newmark displacement. The outcome is a map in which to each siteis related a spatial probability distribution for the expected displacement in response to seismic loading.Results of the experiments show a high grade of uncertainty in the application of the Newmarkanalysis both for the deterministic and probabilistic approach in a complex geological setting suchas the high Sele valley, quite common in the Southern Apennines. They show a strong dependence onthe reliability of the spatial data used in input, so that, when the model is used at basin scale,results are strongly influenced by local environmental condition (e.g., topography, lithology, groundwatercondition) and decrease the model performance.     

Investigating Landslides Caused by Earthquakes – A Historical Review

Post-earthquake field investigations of landslide occurrence have provided a basis for understanding, evaluating, and mapping the hazard and risk associated withearthquake-induced landslides. This paper traces thehistorical development of knowledge derived from these investigations. Before 1783, historical accounts of the occurrence of landslides in earthquakes are typically so incomplete and vague that conclusions based on these accounts are of limited usefulness. For example, the number of landslides triggered by a given event is almost always greatly underestimated. The first formal, scientific post-earthquake investigation that included systematic documentation of the landslides was undertaken in the Calabria region of Italy after the 1783 earthquake swarm. From then until the mid-twentieth century, the best information on earthquake-induced landslides came from a succession ofpost-earthquake investigations largely carried out by formal commissions that undertook extensive ground-based field studies. Beginning in the mid-twentieth century, when the use of aerial photography became widespread, comprehensive inventories of landslide occurrence have been made for several earthquakes in the United States, Peru, Guatemala, Italy, El Salvador, Japan, and Taiwan. Techniques have also been developed for performing ``retrospective' analyses years or decades after an earthquake that attempt to reconstruct the distribution of landslides triggered by the event. The additional use of Geographic Information System (GIS) processing and digital mapping since about 1989 has greatly facilitated the level of analysis that can applied to mapped distributions of landslides. Beginning in 1984, syntheses of worldwide and national data on earthquake-induced landslides have defined their general characteristics and relations between their occurrence and various geologic and seismic parameters. However, the number of comprehensive post-earthquake studies of landslides is still relatively small, and one of the most pressing needs in this area of research is for the complete documentation of landslides triggered by many more earthquakes in a wider variety of environments.     

An scientific evaluation of annual earthquake prediction ability

Introduction There have been nearly 40 years for earthquake prediction since the research on earthquake prediction was carried out in plan by some advanced countries since 1960s. For the hard long process of earthquake prediction, Alen, American famous scientist and former president of the evaluation commission of earthquake prediction in California, USA, said that the difficulty of earthquake prediction is more than the expected and the practical progress of earthquake prediction is more sl…     

两个冰期-间冰期旋回的黄土记录及其古气候意义

北京邻区枣沟、斋堂和赤峰黄土－古土壤剖面粒度和磁化率变化在幅度和相位上都有明显的差异。在两个冰期－间冰期旋回，磁化率记录具有冰量变化模式，而粒度记录具有轨道周期特点，粒度和磁化率之间的相位关系在从冰期向间冰期转换和冰期向间冰期过渡的过程中，既有滞后也有超前的表现，很难单纯以成土作用来解释。由于黄土粒度主要反映粉尘源区环境和古风场强度的变化，而磁化率主要记录的是沉积区的成壤作用，反映夏季风的强度变化，因此剖面粒度和磁化率变化的不协调说明古风场和粉尘源区变化与粉尘沉积区气候变化之间不统一。这可能意味着控制夏季风强度变化和控制冬季风强度变化的机制存在差异。     

金沙江干热河谷土地荒漠化评价方法研究

什么样的退化土地才是荒漠化土地，土地荒漠化的发生发展以及程度和区别等问题的定量确定，至今有关报道甚少。干热河谷是我国西南地区特殊的生态环境类型，自然资源丰富，但土地荒漠化问题十分突出，这一现象的定量认识尤为重要。针对土地景观生态系统的复杂和模糊性，在建立评价指标的基础上，采用模糊综合评判的方法，对土地荒漠化程度进行定量评价，为荒漠化土地的预防和防治提供科学依据和决策支持。     

关于水资源承载力理论与方法的研究

本文首先明确了水资源承载力的基本概念 ,指出可持续发展理论、水 -生态 -社会经济复合系统理论、二元模式下的水文循环机制和过程是水资源承载力研究的理论基础 ,对水资源承载力研究的基本内容、评价指标体系的建立和评价方法进行了较全面的概括和总结。     

吉林省通榆县旅游资源模糊评价研究

该文基于模糊数学的理论和方法 ,从不同角度、不同层次对吉林省通榆县的旅游资源进行综合评价 ,并针对旅游资源特征 ,提出了发展旅游业的基本构思。     

大连市城市内部居住环境评价的空间结构——基于面源模型的分析

以大连市为例 ,首先利用ARC/INFO软件将研究地区划分成 162个元胞作为评价的基本空间单元 ,建立了居住环境评价的面源模型。其次利用MDS方法确定了评价因子、列联表法验证了居民属性与居住环境评价之间的相互独立程度、因子分析方法探讨了居住环境评价结构的平行性。最后应用GIS对居住环境评价空间分异现象进行了分析。