A statistical method to evaluate homogeneity of structural populations

For any specific rock unit in a discontinuous rock mass, the determination of structural domain boundaries is important because geologic and hydrologic properties vary from one domain to another. A domain can be considered as a structural population characterized by a distinct pattern of structure orientations (i.e., fracture, bedding, or foliation orientations).Boundaries are usually determined by comparing samples of structural data, each of which consists of a Schmidt plot that commonly displays at least 150 poles to fractures. When fracture orientations appear dispersed and random on the plots, visual comparisons are not sufficient to determine whether the samples were obtained from the same structural domain. An appropriate x ² test has been adapted to this situation and is capable of evaluating the homogeneity of structural populations. The method uses a contingency table analysis based on the frequencies of fracture poles that occur in corresponding patches on the Schmidt plots being compared.     

A physical statistical approach to erosion

Erosion is a complex process consisting of many components such as surface runoff, impact of raindrops, wind forces, soil and rock mechanics, etc. Trying to integrate all these processes into a physical model seems to be hopeless. In order to understand the variety of natural shapes and patterns produced by erosion we present an integrated statistical approach. Our model is based on simple physical constraints for the separation of amalgamated particles (abrasion) and for the movement of loose particles (denudation) and on the laws of statistics. After some simplifications, we obtain a nonlinear system of partial differential equations which is solved using finite volume techniques. The model is suitable for the formation of different types of rill systems and the episodic behaviour of erosion processes, a kind of self-organized criticality. Besides effects of inhomogeneities, e.g. the formation of terraces can be investigated.     

Lessons from Ontake-san: A comparative analysis of debris avalanche dynamics

Dynamic aspects of the long runout Ontake-san debris avalanche are evaluated by a comparison of several models. An unsteady numerical model assumes two-dimensional flow of an incompressible biviscous or Newtonian fluid, represented as a continuum with a free surface. Internal deformation of the flowing mass is considered, as well as boundary resistances. Thus flow thinning and deposit shape as well as flow kinematics may be modeled. Parameters are adjusted to match observed runout, with additional constraints on velocity and emplacement time. With abundant constraints for Ontake-san, from careful field investigations by Japanese research teams, our analysis indicates that a substantial decrease in flow resistance occurred as a function of displacement. Constant-property models that match runout tend to overestimate the peak velocities and to underestimate the emplacement times. A staged increase in mobility in both constant volume and variable volume models leads to results consistent with field data. Runout in a channel overflow area was also modeled. Qualitatively similar results have been obtained by other researchers using simple sliding block models with empirical parameters, a slide block model with rational parameter selection, a modified flood simulation, and a multi-element frictional slide model. The relative merits of these models are compared.

The field mechanisms associated with this mobility increase with displacement are poorly understood, but the question is now identified as a target for future research at debris avalanche sites, and some plausible mechanisms are considered. The main reason probably involves the entrainment of river water and saturated sediment, leading to enhanced efficiency of fluid pressure mechanisms with undrained shear; in addition, progressive shearing reduced the mean particle size and angularity, and the cohesion and friction (and apparent viscosity) of avalanche debris near the wetted perimeter. Hydroplaning — the shearing of water films and slurries — may have occurred locally.     

A fractal comminution approach to evaluate the drilling energy dissipation

The drilling comminution is theoretically and experimentally analysed by a fractal approach. An extension of the Third Comminution Theory is developed to evaluate the energy dissipation in the process: it occurs in a fractal domain intermediate between a surface and a volume. The theoretical assumption of a material ‘quantum’ is experimentally observed. The experimental fragment analysis evidences the characteristic size of separation between primary cutting and secondary milling. A global power balance for the drilling process is also presented and permits the prediction of drilling velocity. It shows also how the dissipation energy density (drilling strength) is not a constant parameter, but decreases considerably with the size scale. Copyright © 2002 John Wiley & Sons, Ltd.     

巴东县新城区冲沟泥石流危险度评价

根据对巴东城区泥石流特征的调查和分析,本文选取了8个因子评价冲沟泥石危险度,采用模糊数学方法建立危险度评价模型,并对城区三条大型冲沟(白岩沟、铜盆溪、黄家大沟)的泥石流危险度作出评价并得到结果,这对预防和治理巴东新城区的泥石流具有重要意义。     

Modeling of debris avalanche and generated water waves: Application to real and potential events in Montserrat

Tsunamis generated by a sudden entry of debris avalanches into the sea have caused some of the worst natural disasters in historic times. The evolution of the Soufrière Hill volcano's activity in Montserrat, Lesser Antilles, could lead to a dome collapse generating a tsunami. Two scenarios have been simulated here. In the first case, the potential entry into the sea of a debris mass of 40 millions of m³ at the mouth of the Tar River Valley, towards the East has been considered. In this case, the debris avalanche is approximated as a fluid entering the sea with a given front height and a given velocity. Sensitivity tests have shown that the simulated water wave is very sensitive to the imposed initial conditions. In order to have a more accurate source term in the tsunami model, we have developed here a numerical debris avalanche model. This model takes into account a Coulomb-type friction law and solves the vertically integrated long wave equations. A first application of this model has been made to simulate the 26^th December 1997 debris avalanche with an estimated volume of 60 millions of m³ that occurred in the White River valley, South of Montserrat. Preliminary results show that the debris avalanche path is very sensitive to the considered value of the friction angle 5. An empirical value of 5 lower than 15∘ i. e. less than the value expected for debris avalanches, is required to reproduce the great mobility of this avalanche.     

A new simple approach to evaluate pedogenic clay transformation in a Vertic Calcisol

The aim of this study is to characterize the pedogenic clay minerals by using simple approach: mixing mineralogical and geochemical findings.The fine clay fractions (< 0.1 μm) of a Vertic Cambisol profile were studied by means of X-ray diffraction (XRD), infrared spectroscopy (FTIR) and cation exchange capacity (CEC).Qualitative and quantitative mineralogical compositions of the clay mixture were determined.Moreover, chemical equilibria and thermodynamic stabilities of minerals (calcite, gypsum, kaolinite, smectites and illites) were studied using results of ionic activities obtained from total concentration of various aqueous species in water extracts from soil-saturated pastes.XRD analysis shows a good homogeneity in the mineralogical composition of the soil material, with depth of soil profiles. The identified clay minerals are mainly illite–smectite mixed layers (I/S) and kaolinite. The chemical analysis of saturated paste extracts with clay minerals shows a slight undersaturation of the illitic phase while smectites and also calcite and gypsum reach the thermodynamic equilibrium along the soil profile.     

A terrestrial record of Last Interglacial climate preserved by voluminous debris avalanche inundation in Taranaki,New Zealand

At Airedale Reef, western North Island, New Zealand, a ca. 4 m thick volcanogenic debris avalanche deposit has facilitated the preservation of an enveloping sequence of peats with interbedded andesitic tephras spanning marine isotope (MIS) 5. The sequence closely overlies a wave‐cut terrace correlated to MIS 5e and, in turn, is overlain by andic beds with tephra interbeds including the Rotoehu and Kawakawa tephras deposited during early MIS 3 and mid‐MIS 2, respectively. Pollen analysis of the organic sequence shows a coherent pattern of fluctuating climate for the Last Interglacial–Last Glacial transition that corresponds with marine isotope stratigraphy and supports the contention that orbital variations were a primary factor in late Quaternary southern mid‐latitude climate change. A five‐stage subdivision of MIS 5 is clearly recognised, with marine isotope substage (MISS) 5b drier than MISS 5d, and the cooling transition from 5a to MIS 4 also may have been comparatively dry and characterised by natural fire, perhaps associated with volcanism. Several other examples of volcanic impact on vegetation and the landscape are evident. The Airedale Reef sequence exhibits strong similarities with fragmentary MIS 5 pollen records preserved elsewhere in New Zealand and enables the proxy record of southern mid‐latitude climatic variability during the Last Interglacial–Glacial cycle to be extended. Copyright © 2004 John Wiley & Sons, Ltd.     

Stress integration approach to evaluate damping ratio in torsional tests

The complexity of determining strain associated with shear modulus and damping ratio in torsional tests has been resolved by means of several approaches. The stress integration approach is adequate when generating the plots of equivalent radius ratio versus strain more effectively over any range of strains in resonant column and torsional shear (RC/TS) tests. The stress integration approach was applied for hyperbolic, modified hyperbolic, and Ramberg–Osgood models in evaluating damping ratio. This study showed that using a single value of equivalent radius ratio in evaluating damping ratio is not appropriate. The combined hysteretic‐nonviscous damping model was developed and employed to consider the increased damping behavior at small strains using the stress integration approach. The results suggest that adding viscous behavior has no significant effect strain calculations in RC/TS testing. Copyright © 2010 John Wiley & Sons, Ltd.     

Large-scale assessment of avalanche and debris flow hazards in the Sakhalin region,Russian Federation

We explore the challenges of avalanche and debris flow hazard assessment for urban areas exposed in the Sakhalin region. Avalanches are a threat to more than 60 settlements in the region and debris flows to more than 30. Data are provided for avalanche and debris flow events that occurred in the Sakhalin region between 1928 and 2015. In this paper, the method for the design of hazard maps for snow avalanches and debris flows is described, providing the starting point for any planning constraints in general settlement planning schemes. These maps further allow conducting an assessment of avalanche and debris flow risk within a short time period for a larger territory and at minimum cost.

     

A geochemical approach to constraining the formation of glassy fallout debris from nuclear tests

Glassy nuclear fallout debris from near-surface nuclear tests is fundamentally reprocessed earth material. A geochemical approach to analysis of glassy fallout is uniquely suited to determine the means of reprocessing and shed light on the mechanisms of fallout formation. An improved understanding of fallout formation is of interest both for its potential to guide post-detonation nuclear forensic investigations and in the context of possible affinities between glassy debris and other glasses generated by high-energy natural events, such as meteorite impacts and lightning strikes. This study presents a large major-element compositional dataset for glasses within aerodynamic fallout from the Trinity nuclear test (“trinitite”) and a geochemically based analysis of the glass compositional trends. Silica-rich and alkali-rich trinitite glasses show compositions and textures consistent with formation through melting of individual mineral grains—quartz and alkali feldspar, respectively—from the test-site sediment. The volumetrically dominant glass phase—called the CaMgFe glass—shows extreme major-element compositional variability. Compositional trends in the CaMgFe glass are most consistent with formation through volatility-controlled condensation from compositionally heterogeneous plasma. Radioactivity occurs only in CaMgFe glass, indicating that co-condensation of evaporated bulk ground material and trace device material was the main mechanism of radioisotope incorporation into trinitite. CaMgFe trinitite glasses overlap compositionally with basalts, rhyolites, fulgurites, tektites, and microtektites but display greater compositional diversity than all of these naturally formed glasses. Indeed, the most refractory CaMgFe glasses compositionally resemble early solar system condensates—specifically, CAIs.     

Using saline tracers to evaluate preferential recharge in fractured rocks,Floyd County,Virginia, USA

Potassium chloride (KCl) and potassium bromide (KBr) tracers were used to explore the role of geologic structure on groundwater recharge and flow at the Fractured Rock Research Site in Floyd County, Virginia, USA. Tracer migration was monitored through soil, saprolite, and fractured crystalline bedrock for a period of 3 months with chemical, physical, and geophysical techniques. The tracers were applied at specific locations on the ground surface to directly test flow pathways in a shallow saprolite and deep fractured-rock aquifer. Tracer monitoring was accomplished with differential electrical resistivity, chemical sampling, and physical monitoring of water levels and spring discharge. KCl, applied at a concentration of 10,000 mg/L, traveled 160 m downgradient through the thrust fault aquifer to a spring outlet in 24 days. KBr, applied at a concentration of 5,000 mg/L, traveled 90 m downgradient through the saprolite aquifer in 19 days. Tracer breakthrough curves indicate diffuse flow through the saprolite aquifer and fracture flow through the crystalline thrust fault aquifer. Monitoring saline tracer migration through soil, saprolite, and fractured rock provided data on groundwater recharge that would not have been available using other traditional hydrologic methods. Travel times and flowpaths observed during this study support preferential groundwater recharge controlled by geologic structure.     

2001 debris flow and debris flood in Nam Ko area, Phetchabun province, central Thailand

The factors of the debris flow and debris flood (debris flow-flood) occurrence on 11 August 2001 on the active Nam Ko alluvial fan in Phetchabun province, central Thailand, were studied. Evidences of past activity registered in the alluvial fan, and the debris flow-flood event were reconstructed. The disastrous debris flow-flood event was not the work of the unusual high amount of rainfalls alone, as previously theorized, but is a work of combined factors from the terrain characteristics with specific land covers to the time delay for accumulation of debris and sediments. This combination of factors could lead to a debris flow-flood after a high amount of precipitation. The process could also be worse if a landslide formed a natural dam, then the dam was destroyed under the weight of impounded water. After such a disastrous event, it would take time for more plant debris and sediments in the sub-catchment area to accumulate before the next debris flow-flood.     

西藏帕隆藏布泥石流沟谷纵剖面形态统计分析

沟谷纵剖面形态既表征暴雨泥石流发育的地貌条件，又与水动力相关，是影响泥石流发肓的重要因素。西藏帕隆藏布是典型的冰川泥石流区，其干流然乌至迫龙段右岸分布59条各类泥石流沟。统计分析表明，从帕隆藏布下游段向上游段，这些泥石流沟谷纵剖面形态有由下凹抛物线形向上凸抛物线形演变的趋势，形态指数N有由大变小之趋势，反映帕隆藏布河谷地貌演化溯源传递的进程。按特大型、一般性、潜在型泥石流沟的顺序，有纵剖面形态由凹至凸、N值由大至小的总体趋势，反映泥石流活动性与纵剖面形态的关系。冰雪融水型泥石流与雨水型泥石流相比，N值较小，纵剖面形态偏凸，表明了其特殊性。     

A quantitative approach for debris flow inception and propagation analysis in the lead up to risk management

Landslides - This paper presents a quantitative analysis of debris flows in weathered gneiss through a methodology to identify key aspects in the lead up to risk management. The proposed...     

A statistical approach for determining the environment impact of surface sediments from the Dongting Lake area,central China

The Dongting Lake, the second biggest freshwater lake in China, consists of three wetlands of national importance, namely the East Dongting Lake, the South Dongting Lake, and the West Dongting Lake. Surface sedi-ments were sampled from 57 locations across the lake. Nutrient concentrations [total organic carbon (TOC), total N (TN) and total P (TP)] and 16 element concentrations (Al, As, B, Ca, Cd, Cr, Cu, K, Fe, Hg, Mn, Ni, Pb, Si, Ti and Zn) in the sediments were measured to investigate the impact of industrialization along the lake's coastline and sev-eral tributaries on the profiles of nutrients and heavy metals in the lake's surface sediments. R-mode cluster analysis (CA) was used to integrate geochemical data. The result showed that euthophication of the Dongting Lake resulted mainly from TN and TOC. The main polluting trace metals are Hg, As, Cd, Zn, Pb and Mn, which are largely ad-sorbed on clay minerals or Fe/Mn oxides, or deposited as carbonates. Principal component analysis (PCA) revealed the source of micropollutants. The worst affected district by heavy metals is the East Dongting Lake, the pollution sources may originate mainly from the Xiangjiang drainage area. The results demonstrated that multivariate methods are the potentially great tools for the interpretation of the environmental data on lake sediments.     

Using multivariate statistical analyses to evaluate groundwater contamination in the northwestern part of Saudi Arabia

Chemical characteristics of groundwater in the Midyan Basin (northwestern Saudi Arabia) were investigated and evaluated. A total of 72 water samples were collected from existing shallow wells and analyzed for different elements. Two multivariate statistical methods, hierarchical cluster analysis (HCA) and principal components analysis (PCA), were applied to a subgroup of the data set in terms of their usefulness for groundwater classification, and to identify the processes controlling groundwater geochemistry. The subgroup consisted of 46 water samples out of 72 samples and 24 variables included major elements (Ca²⁺, Na⁺, Mg²⁺, K⁺, Cl^?, HCO₃ ^?, NO₃ ^?, SO₄ ^2?), minor and trace element (SiO₂, Al, As, B, Ba, Cd, Cr, F, Fe, Mo, P, Pb, Sb, Sn, Ti, and V). For water samples, four geochemically distinct clusters (i.e., C1, C2, C3 and C4) have been observed by hierarchical cluster analysis. Cr, F and Pb are the dominant ions in cluster C2. Al, As, Cd, Mo, Sb and Ti are the dominant ions in cluster C3, while B, Ca, Cl, HCO₃, K, Mg, Na, SO₄ and V are identified as dominant ions in the cluster C4. In the PCA, a total of five components are extracted form the data set, which explained 73.37 % of the total data variability. Among them the first component reveals strong associations between As, B, Cd, Cr, F, Mo, Pb, Sb and Ti. The second component reveals the associations between Ca, Cl, HCO₃, Mg, Na, SO₄ and V.     

A statistical approach to evaluating distance metrics and analog assignments for pollen records

The modern analog technique typically uses a distance metric to determine the dissimilarity between fossil and modern biological assemblages. Despite this quantitative approach, interpretation of distance metrics is usually qualitative and rules for selection of analogs tend to be ad hoc. We present a statistical tool, the receiver operating characteristic (ROC) curve, which provides a framework for identifying analogs from distance metrics. If modern assemblages are placed into groups (e.g., biomes), this method can (1) evaluate the ability of different distance metrics to distinguish among groups, (2) objectively identify thresholds of the distance metric for determining analogs, and (3) compute a likelihood ratio and a Bayesian probability that a modern group is an analog for an unknown (fossil) assemblage. Applied to a set of 1689 modern pollen assemblages from eastern North America classified into eight biomes, ROC analysis confirmed that the squared-chord distance (SCD) outperforms most other distance metrics. The optimal threshold increased when more dissimilar biomes were compared. The probability of an analog vs no-analog result (a likelihood ratio) increased sharply when SCD decreased below the optimal threshold, indicating a nonlinear relationship between SCD and the probability of analog. Probabilities of analog computed for a postglacial pollen record at Tannersville Bog (Pennsylvania, USA) identified transitions between biomes and periods of no analog.