GIS based landslide susceptibility mapping using a fuzzy logic approach: A case study from Ghurmi-Dhad Khola area, Eastern Nepal

Landslides cause extensive loss of life and property in the Nepal Himalaya. Since the late 1980s, different mathematical models have been developed and applied for landslide susceptibility mapping and hazard assessment in Nepal. The main goal of this paper is to apply fuzzy logic to landslide susceptibility mapping in the Ghurmi-Dhad Khola area, Eastern Nepal. Seven causative factors are considered: slope angle, slope aspect, distance from drainage, land use, geology, distance from faults and folds, soil and rock type. Likelihood ratios are obtained for each class of causative factors by comparison with past landslide occurrences. The ratios are normalized between zero and one to obtain fuzzy membership values. Further, different fuzzy operators are applied to generate landslide susceptibility maps. Comparison with the landslide inventory map reveals that the fuzzy gamma operator with a γ-value of 0.60 yields the best prediction accuracy. Consequently, this operator is used to produce the final landslide susceptibility zonation map.     

基于地球物理数据融合的大兴安岭中段东缘地壳结构研究

位于中亚造山带东段的兴安地块和松辽锡林浩特地块被晚古生代贺根山- 黑河缝合带分开。随后,大兴安岭与松辽盆地被中新生代嫩江- 八里罕断裂分开。在大兴安岭中段,这两构造带的位置及板块拼合时间尚不明确。为研究大兴安岭中段东缘重要构造断裂、构造单元及结晶基底属性特征,在扎兰屯- 阿荣旗地区采集处理一条长60 km的重力、磁法和大地电磁数据,重新处理了120万扎兰屯幅、阿荣旗幅区域布格重力异常数据。通过多种地球物理数据融合,解译了7条重要断裂,其中庞家街断裂和红星断裂是控制贺根山- 黑河缝合带的深大断裂。北西向阿伦河断裂为深大断裂,至少切割到中地壳。发现了两个中地壳低阻带,其中C2异常解释为贺根山- 黑河缝合带。通过125万阿荣旗幅地质填图资料,证实了地球物理数据融合的推断结果,为大兴安岭中段东缘构造带演化研究提供了重要支撑。     

基于流动电位正演模型的非饱和带水流过程监测

为了获取非饱和带水流过程的信息,借助流动电位正演模型,通过数值实验探讨非降雨和降雨两种条件下非饱和带流动电位和水流过程的关系,然后用南京中山植物园试验场地野外观测的流动电位和张力数据加以对比和验证。野外试验表明:流动电位可以有效地反映非饱和带水流过程。在夏季无降雨入渗的条件下,日周期变化的地表地下温度差导致水分的运动,流动电位准确地指示了非饱和带含水量和毛细压力的变化情况,从而指示出了水分运移的方向;在夏季有降雨入渗的条件下,降雨锋面推进之处,含水量和流动电位同时有明显的响应,进而根据不同位置的流动电位对降雨入渗响应的时刻差,直接求出入渗锋面的推进速度。     

基于模糊逻辑的中甸岛弧斑岩型铜矿定位预测

文章选择中甸岛弧地区中比例尺地表填图所圈定的侵入岩及火山岩、航磁解译构造格架及汇水盆地沉积物多元素异常作为斑岩型铜矿定位预测的主要方法,总结提出了该区斑岩型铜矿的定位预测准则,并根据该准则在GIS平台上基于模糊逻辑模型进行了模糊成员权重赋值和模糊推理网络构建。通过模糊推理计算得到该区不同高度、不同方向航磁解译构造的交汇部位以及不同元素的组合异常特征,最终确定了该区可以发现斑岩型铜矿的模糊概率分布图。该区主要矿床如普朗、红山和雪鸡坪等均处于高模糊概率分布区,经野外检查验证发现普上和地苏嘎两处斑岩铜矿矿化新区。     

基于多源遥感与航空物探数据的岩性分类方法

遥感影像可以获取地表岩性的光谱、色调、纹理等信息,但其所提取的信息局限于地表,对深层地质问题解释并无明显优势;航空物探数据则对地下深部异常体信息的提取更具优势。单一某类数据难以满足基础地质、资源勘查等方面复杂应用的需求。因此,提出一种遥感与航空物探信息联合分析方法,以新疆某地为研究区,结合遥感与航空物探多源数据特征,基于随机森林方法对研究区岩性进行分类。结果表明,与使用单一某类数据相比,遥感与航空物探信息联合分析方法能提高岩性分类精度。该方法对于推动遥感与航空物探技术在地质填图中的精细化应用,具有一定实用价值与指导意义。     

模拟降雨条件下坡面流水动力学特性研究

为探明降雨条件下沙黄土坡面水流水动力学特性,以流体力学和泥沙运动力学理论为依据,通过5个坡度和5个雨强组合条件下室内模拟降雨试验,系统研究了坡面水流水力参数的变化规律。结果表明,降雨条件下坡面薄层水流雷诺数均小于580,处于层流失稳区;水流流型随雨强和坡度的变化而发生转捩,当坡度较缓、雨强较小时,床面形态处于低能态区和过渡区,床面出现沙纹现象,水流宏观上呈缓流,反之,坡度较陡、雨强较大时,床面由沙纹和沙垄向动平床过渡,宏观上多呈急流;并根据薄层水流阻力组成特点,推导出沙黄土坡面薄层水流阻力计算公式。验证结果表明,该式误差较小,可为坡面侵蚀预报模型的构建提供参考。     

基于模糊逻辑法的冀西北地区铅锌银多金属矿定位预测

模糊逻辑空间决策模型在变量取值上不是采用二态法将研究区分为成矿有利区和成矿不利区两部分,而是根据地质数据的规律取连续变化的隶属度赋值,有效避免了有用地质信息的丢失。笔者在GIS平台上利用Arc-SDM模块对冀西北地区的地质、地球化学、地球物理等资料进行了处理,利用证据权法进行了线缓冲形成的证据层与矿床（点）之间的亲近度分析,在此基础上采用列表法对原始地质变量进行了直观模糊隶属度赋值。模糊逻辑的预测结果表明,在圈出的仅占研究区面积13.2%的靶区范围内有85%的已知矿床（点）出现,与已知矿床（点）吻合程度高,预测效果理想,其结果可用于指导下一步找矿工作。     

Comments on “a statistical prediction technique for deriving contour maps from geophysical data”

Mathematical Geosciences -     

Quantifying the effects of subsurface heterogeneity on hillslope runoff using a stochastic approach

The role of heterogeneity and uncertainty in hydraulic conductivity on hillslope runoff production was evaluated using the fully integrated hydrologic model ParFlow. Simulations were generated using idealized high-resolution hillslopes configured both with a deep water table and a water table equal to the outlet to isolate surface and subsurface flow, respectively. Heterogeneous, correlated random fields were used to create spatial variability in the hydraulic conductivity. Ensembles, generated by multiple realizations of hydraulic conductivity, were used to evaluate how this uncertainty propagates to runoff. Ensemble averages were used to determine the effective runoff for a given hillslope as a function of rainfall rate and degree of subsurface heterogeneity. Cases where the water table is initialized at the outlet show runoff behavior with little sensitivity to variance in hydraulic conductivity. A technique is presented that explicitly interrogates individual realizations at every simulation timestep to partition overland and subsurface flow contributions. This hydrograph separation technique shows that the degree of heterogeneity can play a role in determining proportions of surface and subsurface flow, even when effective hillslope outflow is seen. This method is also used to evaluate current hydrograph separation techniques and demonstrates that recursive filters can accurately proportion overland and base-flow for certain cases.     

Structural framework of the Jaibaras Rift,Brazil, based on geophysical data

The Cambro-Ordovician Jaibaras Rift is a NE–SW trending elongated feature, controlled by the Transbrasiliano lineament, locally known as Sobral-Pedro II shear zone (SPIISZ). An integrated study of geophysical data (gammaspectrometry, magnetometry and gravimetry) was undertaken in the Jaibaras Rift area, between Ceará Central (CCD) and Médio Coreaú domains (MCD), northwest Borborema Province. Geophysical data were interpreted qualitatively and quantitatively in order to understand the tectono-magmatic relations and rift formation based on the main geophysical lineaments, source geometry and depth, and separation of geophysical domains. In addition, a 2D gravity model was generated. The results show a structural partition characterized by NE–SW lineaments and E–W inflexions, where CCD presents a relatively mild magnetic field, whilst the MCD field is more disturbed. The Jaibaras Rift is characterized by positive magnetic and gravity anomalies. The SPIISZ, which corresponds to the SE fault edge of the Jaibaras Rift, is marked by strong magnetic dipoles and strong gravity gradients in the profile, showing the deep character of the Transbrasiliano lineament in the region. The Café-Ipueiras fault, at the NW edge of the rift, is well marked in gravity profiles, but displays low contrast of the magnetic field. Interpretation of the gravimetric anomaly map allowed to recognizing the main NE–SW axis, with alternation of maxima and minima in MCD. A regional gravity gradient reveals significant lateral density variation between the MCD and CCD perpendicular to the SPIISZ, emphasizing it as a main continental suture zone between crustal blocks.     

Kinematics of a deep-seated landslide derived from photogrammetric, GPS and geophysical data

The deep-seated landslide located at the intersection of the Gradenbach and Möll valleys near Döllach, Austria, has been the target of many previous investigations [Kronfellner-Kraus, G., 1980. Neue Untersuchungsergebnisse in Wildbächen — Der Talzuschub in Abhängigkeit von Niederschlägen. Int. Symp. Interpraevent Bad Ischl 1: 179–192; Weidner, S., Moser, M., Lang, E., 1998. Influence of hydrology on sagging of mountain slopes (“Talzuschübe”) — New results of time series analysis. 8th International IAEG Congress, Vancouver, Canada, Balkema, Rotterdam, 1259–1266; Weidner, S., 2000. Kinematik und Mechanismus tiefgreifender alpiner Hangdeformationen unter besonderer Berücksichtigung der hydrologischen Verhältnisse. Dissertation, Friedrich–Alexander-Universität Erlangen–Nürnberg, 246.]. In this paper, photogrammetric, GPS and geophysical data have been utilized to derive a constraint on the kinematics of the sagging process. The photogrammetric models have been based on aerial photographs from 1962 and 1996. Displacement vectors of about 50 individual characteristic points have been determined; these clearly show the area of the sagging slope. From 1999 to 2004, eleven GPS campaigns have been carried out, yielding very accurate displacement vectors at four monitoring points. Information about the internal structure of the slope was determined using seismic surveys.

The displacements observed by photogrammetry and GPS have shown a rather uniform movement of the whole sagging slope, with a slight longitudinal compression of 0.6%. In order to extend the kinematic consideration to 3D, a special form of the equation of continuity (conservation of mass) has been applied to the 1962–1996 photogrammetric data, together with the cross-sections derived from the seismic data. The average velocities through cross-sections have been calculated by integrals of the mass-balance above and below these cross-sections. Changes of the total rock mass, due to accumulation and especially to erosion, as well as an overall compaction of 1.5% between 1962 and 1996, have been considered. The calculated average velocities through a cross-section and the surface velocities independently determined by photogrammetry agree within an uncertainty of 15%. The results indicate a block movement with shear concentration at the basal sliding surface.     

基于支持向量机与地球物理测井资料的煤体结构识别方法

煤体结构作为煤层勘探开发研究的重点参数之一,影响着煤层产能,有效识别煤层煤体结构至关重要.本文利用支持向量机算法,以地球物理测井资料为基础进行煤体结构识别,并以沁水煤田柿庄北区3号层为例,对该区块进行煤体结构类型分类,利用支持向量机的双二分类与"一对多"分类两种建模模式,建立基于测井曲线的煤体结构识别模型,再利用交叉验证评价模型的泛化性,并对该模型用未参与建模数据进行准确性评价.结果表明,应用支持向量机算法的两种模式能有效识别煤体结构,模型具有泛化性与准确性,且"一对多"分类模式精度更高,在对有利产出煤和不利产出煤的区分上效果突出,对有利产出煤的具体类型区分上具有准确性,可对后续压裂施工提供指导.总体上,基于支持向量机算法和地球物理测井资料建立的煤体结构识别模型对煤层气勘探开发有指导意义,具有实际应用价值.     

The typology of Irish hard-rock aquifers based on an integrated hydrogeological and geophysical approach

Groundwater flow in hard-rock aquifers is strongly controlled by the characteristics and distribution of structural heterogeneity. A methodology for catchment-scale characterisation is presented, based on the integration of complementary, multi-scale hydrogeological, geophysical and geological approaches. This was applied to three contrasting catchments underlain by metamorphic rocks in the northern parts of Ireland (Republic of Ireland and Northern Ireland, UK). Cross-validated surface and borehole geophysical investigations confirm the discontinuous overburden, lithological compartmentalisation of the bedrock and important spatial variations of the weathered bedrock profiles at macro-scale. Fracture analysis suggests that the recent (Alpine) tectonic fabric exerts strong control on the internal aquifer structure at meso-scale, which is likely to impact on the anisotropy of aquifer properties. The combination of the interpretation of depth-specific hydraulic-test data with the structural information provided by geophysical tests allows characterisation of the hydrodynamic properties of the identified aquifer units. Regionally, the distribution of hydraulic conductivities can be described by inverse power laws specific to the aquifer litho-type. Observed groundwater flow directions reflect this multi-scale structure. The proposed integrated approach applies widely available investigative tools to identify key dominant structures controlling groundwater flow, characterising the aquifer type for each catchment and resolving the spatial distribution of relevant aquifer units and associated hydrodynamic parameters.     

北京西郊玉泉山地区岩溶水强径流路径地球物理分析

为研究北京西郊玉泉山地区岩溶水径流路径,需查明区内地层结构和断裂构造发育情况,故在玉泉山周边地区开展了综合地球物理勘查工作。完成1∶25000面积性重力测量3670点,在重力数据解释推断成果基础上,有针对性地布设可控源音频大地电磁测深(CSAMT)剖面测量5.1 km及微动测深点4个。综合研究了基岩起伏形态和构造展布特征,新解释推断了10条可能存在的断裂构造。结合区域水文地质资料,对主要断裂的水文地质意义进行了分析,形成了玉泉山地区岩溶水强径流路径新的认识,部分成果与最新的同位素水化学研究成果一致。本研究为玉泉山泉恢复确定合理的回灌方案提供了地球物理依据。     

Prospectivity of Western Australian iron ore from geophysical data using a reject option classifier

There has recently been a rapid growth in the amount and quality of digital geological and geophysical data for the majority of the Australian continent. Coupled with an increase in computational power and the rising importance of computational methods, there are new possibilities for a large scale, low expenditure digital exploration of mineral deposits. Here we use a multivariate analysis of geophysical datasets to develop a methodology that utilises machine learning algorithms to build and train two-class classifiers for provincial-scale, greenfield mineral exploration. We use iron ore in Western Australia as a case study, and our selected classifier, a mixture of a Gaussian classifier with reject option, successfully identifies 88% of iron ore locations, and 92% of non-iron ore locations. Parameter optimisation allows the user to choose the suite of variables or parameters, such as classifier and degree of dimensionality reduction, that provide the best classification result. We use randomised hold-out to ensure the generalisation of our classifier, and test it against known ground-truth information to demonstrate its ability to detect iron ore and non-iron ore locations. Our classification strategy is based on the heterogeneous nature of the data, where a well-defined target “iron-ore” class is to be separated from a poorly defined non-target class. We apply a classifier with reject option to known data to create a discriminant function that best separates sampled data, while simultaneously “protecting” against new unseen data by “closing” the domain in feature space occupied by the target class. This shows a substantial 4% improvement in classification performance. Our predictive confidence maps successfully identify known areas of iron ore deposits through the Yilgarn Craton, an area that is not heavily sampled in training, as well as suggesting areas for further exploration throughout the Yilgarn Craton. These areas tend to be more concentrated in the north and west of the Yilgarn Craton, such as around the Twin Peaks mine (~ 27°S, 116°E) and a series of lineaments running east–west at ~ 25°S. Within the Pilbara Craton, potential areas for further expansion occur throughout the Marble Bar vicinity between the existing Spinifex Ridge and Abydos mines (21°S, 119–121°E), as well as small, isolated areas north of the Hamersley Group at ~ 21.5°S, ~ 118°E. We also test the usefulness of radiometric data for province-scale iron ore exploration, while our selected classifier makes no use of the radiometric data, we demonstrate that there is no performance penalty from including redundant data and features, suggesting that where possible all potentially pertinent data should be included within a data-driven analysis. This methodology lends itself to large scale, reconnaissance mineral explorations, and, through varying the datasets used and the commodity being targeted, predictive confidence maps for a wide range of minerals can be produced.     

盾构法隧道施工变形智能模糊控制方法研究

在对盾构施工变形规律认识的基础上,引入了智能控制学科的思想与方法,采用模糊逻辑控制技术建立了变形的智能模糊逻辑控制系统模型,并进一步在地铁盾构法区间隧道工程中进行了初步实证研究。控制分析结果表明,采用本文提出的理论控制模型能够实现定量化盾构诸施工参数的主动与实时控制。