Spectral Simulation and Conditioning to Local Continuity Trends in Geologic Modeling     

Tingting Yao  Craig Calvert  Tom Jones  Glen Bishop  Yuan Ma  Lincoln Foreman 《Mathematical Geology》2006,38(1):51-62

Spectral simulation has gained application in building geologic models due to the advantage of better honoring the spatial continuity of petrophysical properties, such as reservoir porosity and shale volume. Distinct from sequential simulation methods, spectral simulation is a global algorithm in the sense that a global density spectrum is calculated once and the inverse Fourier transform is performed on the Fourier coefficient also only once to generate a simulation realization. The generated realizations honor the spatial continuity structure globally over the whole field instead of only within a search neighborhood, as with sequential simulation algorithms. However, the disadvantage of global spectral simulation is that it traditionally cannot account for the local information such as the local continuity trends, which are often observed in reservoirs and hence are important to be accounted for in geologic models. This disadvantage has limited wider application of spectral simulation in building geologic models. In this paper, we present ways of conditioning geologic models to the relevant local information. To account for the local continuity trends, we first scale different frequency components of the original model with local-amplitude spectrum ratios that are specific to the local trend. The sum of these scaled frequency components renders a new model that displays the desired local continuity trend. The implementation details of this new method are discussed and examples are provided to illustrate the algorithm.  相似文献   

Mesoproterozoic diamondiferous ultramafic pipes at Majhgawan and Hinota, Panna area, central India: Key to the nature of sub-continental lithospheric mantle beneath the Vindhyan basin     

N. V. Chalapathi Rao 《Journal of Earth System Science》2006,115(1):161-183

Amongst all the perceptible igneous manifestations (volcanic tuffs and agglomerates, minor rhyolitic flows and andesites, dolerite dykes and sills near the basin margins, etc.) in the Vindhyan basin, the two Mesoproterozoic diamondiferous ultramafic pipes intruding the Kaimur Group of sediments at Majhgawan and Hinota in the Panna area are not only the most conspicuous but also well-known and have relatively deeper mantle origin. Hence, these pipes constitute the only yet available ‘direct’ mantle samples from this region and their petrology, geochemistry and isotope systematics are of profound significance in understanding the nature of the sub-continental lithospheric mantle beneath the Vindhyan basin. Their emplacement age (∼ 1100 Ma) also constitutes the only reliable minimum age constrain on the Lower Vindhyan Group of rocks. The Majhgawan and Hinota pipes share the petrological, geochemical and isotope characteristics of kimberlite, orangeite (Group II kimberlite) and lamproite and hence are recognised as belonging to a ‘transitional kimberlite-orangeite-lamproite’ rock type. The namemajhagwanite has been proposed by this author to distinguish them from other primary diamond source rocks. The parent magma of the Majhgawan and Hinota pipes is envisaged to have been derived by very small (<1%) degrees of partial melting of a phlogopite-garnet lherzolite source (rich in titanium and barium) that has been previously subjected to an episode of initial depletion (extensive melting during continent formation) and subsequent metasomatism (enrichment). There is absence of any subduction-related characteristics, such as large negative anomalies at Ta and Nb, and therefore, the source enrichment (metasomatism) of both these pipes is attributed to the volatile- and K-rich, extremely low-viscosity melts that leak continuously to semi-continuously from the asthenosphere and accumulate in the overlying lithosphere. Lithospheric/crustal extension, rather than decompression melting induced by a mantle plume, is favoured as the cause of melting of the source regions of Majhgawan and Hinota pipes. This paper is a review of the critical evaluation of the published work on these pipes based on contemporary knowledge derived from similar occurrences elsewhere.  相似文献   

Identification and evaluation of hydrogeochemical processes in the groundwater environment of Delhi, India   总被引：10，自引：0，他引：10  

Manish Kumar  AL. Ramanathan  M. S. Rao  Bhishm Kumar 《Environmental Geology》2006,50(7):1025-1039

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中国大陆科学钻探（CCSD）主孔地区岩石圈热结构   总被引：11，自引：2，他引：11  

吴耀  金振民  欧新功  徐海军  王璐 《岩石学报》2005,21(2):439-450

岩石圈热结构是指地球内部热量在壳幔的配分比例、温度以及热导率和生热率等热学参数在岩石圈中的分布特征。岩石圈的热结构直接影响着岩石的物理性质和流变学性质,同时还控制了化学反应的类型和速度,从而制约着岩石圈的发展和演化。本文在前人CCSD主孔岩石主、微量元素研究基础上,利用Rybach生热率公式计算了钻孔岩石的放射性生热率,并结合岩石热导率的测定研究了CCSD主孔100-2000m岩石的热结构和主孔榴辉岩在不同退变质程度下生热率、热导率的变化:钻孔中岩石的平均生热率为0.95μWm-3,平均热导率为2.96mWm-1K-1。,其中片麻岩生热率高迭1.01-1.7μWm-3,热导率为2.76-2.96mWm-1K-1;基性超基性岩石生热率最低(<0.21μWm-3),热导率则高达3.20mWm-1K-1以上;新鲜榴辉岩生热率、热导率居中,分剐为0.16-0.44μWm-3和3.31-3.85mWm-1K-1。钻孔中榴辉岩生热率、热导率变化主要受岩性控制:从新鲜榴辉岩到完全退变榴辉岩,热导率总体上降低,但从强退变榴辉岩到完全退变榴辉岩,岩石热导率升高;而在此过程中岩石生热率总体上升高,仅当从中等退变质榴辉岩退变为强退变质榴辉岩时,岩石生热率出现降低趋势。在综合研究的基础上预测CCSD主孔5000m深度处温度为139℃,温度范围为131-151℃。根据区域深部地球物理探测成果对CCSD主孔地区岩石圈热结构进行了研究:上地壳底部温度为256℃,中地壳底部温度为492℃,Moho面温度为683℃,岩石圈底部温度为1185℃,来自地幔的热流为44.1mWm-2,对地表热流的贡献率为58%。研究结果表明,由岩石物理方法获得的CCSD主孔地区岩石圈地温曲线与石榴石-二辉橄榄岩包体推断的中国东部地温曲线十分吻合,本文从实验岩石物理学角度为CCSD主孔地区岩石圈热结构研究提供了重要约束  相似文献   

云南省冰雹的时空分布特征   总被引：13，自引：6，他引：13       下载免费PDF全文

杨家康  杞明辉 《气象科技》2005,33(1):41-44

利用近40年的云南省冰雹资料，统计分析了云南省冰雹的时空分布特征，进一步揭示了其活动规律及主要影响因素。研究结果表明：冰雹的季节分布比较复杂，呈现出春季和夏季两个峰值的特点；冰雹的季节分布还与海拔高度有关，低海拔地区为春季多雹型，高海拔地区为夏季多雹型；滇西地区冰雹日数的年际变化特征较滇东地区显著而年代际变化特征没有东部地区站点明显；滇东地区表现出了明显的年代际变化特征，目前处于冰雹相对较少时期。从区域来看，年冰雹日数山区较坝区高，高海拔地区较低海拔地区高。  相似文献   

Estimation of ship velocities from MODIS and OCM     

Rao  N.S. Ali  M.M. Rao  M.V. Ramana  I.V. 《Geoscience and Remote Sensing Letters, IEEE》2005,2(4):437-439

Detection of ships and their tracks in the atmosphere from satellites was earlier demonstrated by Porch, Noone, and Kaufman, among others. In this letter, we have gone one step further to estimate the ship speed and direction by locating them and their tracks from multisatellite imagery. Exhausts from the ships create streaks of clouds in the atmosphere that help identify the same ship from two satellites. Ship velocities are estimated from displacements of ships. We have used optical sensors data from Moderate Resolution Imaging Spectroradiometer (MODIS) and Ocean Color Monitor (OCM) to demonstrate this technique. Estimated velocities of ships are within the expected range. Application of this approach has general interest to the navy, coast guards, shipping corporations, commercial ship owners, and fishermen. More satellite observations can be used to continuously monitor the ship velocities.  相似文献   

How Far Is Too Far? – A Statistical Approach to Context‐contingent Proximity Modeling     

Xiaobai Yao  Jean-Claude Thill 《Transactions in GIS》2005,9(2):157-178

Proximity is a fundamental concept in any comprehensive ontology of space ( Worboys 2001 ). The provision of a context‐contingent translation mechanism between linguistic proximity measures (e.g. “near”, “far”) and metric distance measures is an important topic in current GIS research. After a discussion of context factors that mediate the relationship between linguistic and metric distance measures, we present a statistical approach, Ordered Logit Regression, to the context‐contingent proximity modeling. The approach can predict proximity given the corresponding metric distance and context variables. An empirical case study with human subjects is carried out using this statistical approach. Interpretation and predictive accuracy of the empirical case study are discussed.  相似文献   

Check dam positioning by prioritization of micro-watersheds using SYI model and morphometric analysis — Remote sensing and GIS perspective   总被引：5，自引：0，他引：5  

K. Nooka Ratnam  Y. K. Srivastava  V. Venkateswara Rao  E. Amminedu  K. S. R. Murthy 《Journal of the Indian Society of Remote Sensing》2005,33(1):25-38

Sediment Yield Index (SYI) model and results of morphometric analysis have been used to prioritize watersheds and to locate sites for checkdam positioning in Tarafeni watershed in Midnapur district. West Bengal. Various thematic maps such as land use/land cover, slope, drainage, soil etc. were prepared from 1RS ID LISS III digital data, SOI toposheets of 1:50,000 scale and other reference maps. Morphometric parameters such as bifurcation ratio (R_b). drainage density (D_d), texture ratio (T), length of overland flow (L_o), stream frequency (F_u), compactness coefficient (C_c), circularity ratio (R_c), elongation ratio (E_r), shape factor (B_s) and form factor (R_f) were computed. Automated demarcation of prioritization of micro-watersheds was done by using GIS overlaying technique by assigning weight factors to all the identified features in each thematic map and ranks were assigned to the morphometric parameters. Five categories of priority viz., very high, high, medium, low and very low, were given to all the watersheds in both the methods. Sixty-two micro-watersheds using SYI method and twenty-three micro-watersheds using morphometric have been prioritized as very high priority. Final priority map was prepared by considering the commonly occurred very high-prioritized micro-watersheds in both SYI model and morphometric analysis. Twenty-four suitable sites were identified for check dam construction in 21 highly prioritized watersheds. It is proved that integrated study of SYI model and morphometric analysis yield good result in prioritization of watersheds.  相似文献   

西北区东部一次暴雨的数值模拟试验   总被引：19，自引：23，他引：19  

王劲松  李耀辉  康凤琴  张华 《高原气象》2002,21(3):258-266

运用双向嵌套的中尺度数值预报模式MM5，对1998年7月上旬西北区东部一次暴雨过程进行了高分辨率数值模拟和敏感性试验。结果表明，该模式能较好地模拟这次暴雨过程，对这次暴雨过程相关的中尺度系统的发生发展也作出了较成功的模拟；大尺度及积云对流尺度的凝结潜热在降水过程中是一个主要因子，潜热释放将加热中高层大气，促使高层大气辐散，低层辐合，垂直运动加强，导致较大的降水；初始时刻不同地区低层大气水汽含量的多寡直接对本次暴雨产生影响，并为这次暴雨提供了水汽源；地面水汽和感热的垂直输送为暴雨的发生发展补充了能量。  相似文献   

A HORIZONTAL 2-D HYDRAULIC NUMERICAL MODEL AND IT’S APPLICATIONS TO FLOOD FORECAST     

Minghui YU  Guolu YANG  Jinjun XU 《国际泥沙研究》2002,17(3)

1 INTRODUCTION There were many flood disasters in China in recent years. When the water level in a river is very high, weak parts of its dike may be destroyed resulted in the submersion of the protected land and properties. It is of significance for decision-makers to exactly predict the processes of flood propagation during flood control. There are many modes of dike bursting, such as seepage destroying by overflow on top of dike caused by dike body sinking induced by piping and soil fl…  相似文献