鸡西盆地张新地区浅成侵入体对围岩有机质成熟度及变质程度的影响     

朱占平  刘立  马瑞  宋土顺  邱增凯 《世界地质》2012,31(2):345-350

利用鸡西盆地张新地区西风井揭示的连续剖面,采用镜质体反射率、伊利石结晶度分析测试方法对西风井浅成岩侵入后的上盘围岩有机质成熟度( Ro) 、变质程度进行研究,发现上盘围岩的镜质体反射率随远离辉绿玢岩体的距离增加而减少( 由2. 31%到0. 79%) ; 侵入体对上盘围岩有机质影响最大距离为129. 06 m,是岩体厚度的1. 2 倍; 伊利石结晶度数据显示围岩处于极低级变质程度,围岩的温度随远离辉绿玢岩体的距离增加而降低; 计算得出西风井城子河组地层最大埋藏温度为 259. 24℃,持续时间117. 7 a。最高温度及其持续时间决定围岩的变质程度,是围岩接触变质程度较低的原因。  相似文献   

淮南张集煤矿层滑构造分类及形成机制探讨     

解国爱  姚素平  王光扣  张国明  邱志诚 《大地构造与成矿学》2013,37(1):11-19

通过淮南煤田张集井田层滑构造的具体表现形式分析,对层滑构造进行了系统分类。根据层滑构造的表现形态分为揉皱型和断裂型两种基本类型,根据不同层滑构造的组合形态又可分为书斜式、垒堑式、阶梯状和"y"与反"y"字形等,并采用物理模拟方法对不同层滑构造类型进行了实验研究。运用镜质体的反射率各向异性恢复了矿区构造应力场,张集井田中生代以来至少受到两期构造应力场作用,NWW-SEE方向的拉伸是形成张集井田层滑构造的主要力学机制。  相似文献   

The role of the helicity spectrum function in turbulent dynamo theory     

H. K. Moffatt  M. R. E. Proctor 《地球物理与天体物理流体动力学》2013,107(3-4):265-283

Abstract

It is shown that, for general homogeneous turbulence, the anti-symmetric part of the spectrum tensor can be expressed in terms of a single scalar function H(k,ω) (the helicity spectrum function). Under the first-order smoothing approximation, the coefficients α _ij β _ijk in the expansion of the mean electromotive force in terms of the mean magnetic field are determined; α _ij is a weighted integral of H(k,ω), and β _ijk contains a part β(a)ijk which is likewise a weighted integral of H(k, ω). When the turbulence is axisymmetric, β(a)ijk contains Rädler's (1969a) “Ω ∧ J-effect”. It is shown that when the turbulence is statistically symmetric about a plane perpendicular to the axis of symmetry, then βij = O but the Rädler effect is non-zero. Explicit expressions for αij and βijk are given when the velocity field is generated by random forcing in a rotating medium. Finally, it is shown by means of a local analysis that the Rädler effect, in conjunction with uniform mean shear, can give rise to non-oscillatory dynamo action, and it is argued that this effect may be significant in the well-mixed interior of a stellar convection zone, where by symmetry the α-effect may be weak.  相似文献   

泉州盆地地震效应的二维非线性分析     

董菲蕃  陈国兴  金丹丹 《地震工程与工程振动》2013,33(3)

基于ABAQUS显式有限元并行计算平台,采用大尺度二维精细化有限元非线性分析方法,研究泉州盆地地震效应特征.结果表明:(1)与基岩输入地震动相比,地表峰值加速度总体呈放大效应,且盆地不同位置的放大效应存在明显差异;(2)地表或基岩剧烈起伏及土层横向分布极不均匀处,地震动易产生局部聚集效应,相应地表地震动呈显著放大或缩小效应;地表加速度反应谱产生双峰甚至多峰现象.(3)在土层竖向、横向分布不均匀处,峰值加速度沿深度方向呈非单调递减,加速度反应谱沿深度存在较大差异.场地地震效应的二维非线性分析法能在一定程度上反映特殊场地条件对地震动效应的影响,该结果可为泉州盆地及类似盆地的场地设计地震动参数的确定提供参考依据.  相似文献   

A cloud detection method based on a time series of MODIS surface reflectance images   总被引：1，自引：0，他引：1  

《International Journal of Digital Earth》2013,6(6):157-171

The Moderate Resolution Imaging Spectroradiometer (MODIS)-Terra surface reflectance product (MOD09A1), with bands 1 to 7, is a gridded, eight-day composite product derived from the MODIS-Terra top of atmosphere reflectance swaths. It performs cloud detection and corrects for the effects of atmospheric gases and aerosols. The cloud mask (CM) algorithms for MODIS are based on empirical thresholds on spectral reflectance and brightness temperature. Since the spatial resolution of the thermal band is 1000 m, while that of MOD09A1 is 500 m, many undetected and false clouds are observed in MOD09A1. These errors always result in temporal and spatial inconsistencies in higher-level products. In this paper, a cloud detection algorithm (TSCD) based on a MOD09A1 time series is introduced. Time series cloud detection (TSCD) algorithm is based on the relative stability of ground reflectance and the sudden variations in reflectance that result from cloud cover. The algorithm first searches the clear-sky reference data, and then discriminates clouded and unclouded pixels by detecting a sudden change of reflectance in the blue wavelength and spectral correlation coefficient at the pixel level. Compared with cloud cover assessments obtained from MODIS' original CM, TSCD provides similar or better discrimination in most situations when the land surface changes slowly.  相似文献   

Near‐source seismic hazard and design scenarios     

Eugenio Chioccarelli  Iunio Iervolino 《地震工程与结构动力学》2013,42(4):603-622

Earthquakes damage engineering structures near, relatively to the rupture's size, to the source. In this region, the fault's dynamics affect ground motion propagation differently from site to site, resulting in systematic spatial variability known as directivity. Although a number of researches recommend that records with directivity‐related velocity pulses should be explicitly taken into account when defining design seismic action on structures, probabilistic seismic hazard analysis (PSHA), in its standard version, seems inadequate for the scope. In the study, it is critically reviewed why, from the structural engineering point of view, hazard assessment should account for near‐source effects (i.e., pulse‐like ground motions), and how this can be carried out adjusting PSHA analytically via introduction of specific terms and empirically calibrated models. Disaggregation analysis and design scenarios for near‐source PSHA are also formulated. The analytical procedures are then applied to develop examples of hazard estimates for sites close to strike–slip or dip–slip faults and to address differences with respect to the ordinary case, that is, when pulse‐like effects are not explicitly accounted for. Significant increase of hazard for selected spectral ordinates is found in all investigated cases; increments depend on the fault‐site configuration. Moreover, to address design scenarios for seismic actions on structures, disaggregation results are also discussed, along with limitations of current design spectra to highlight the pulse‐like effects of structural interest. Finally, an attempt to overcome these, by means of disaggregation‐based scenarios specific for the pulse occurrence case, is presented. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

A procedure for generating performance spectra for structures equipped with passive supplemental dampers     

Jack Wen Wei Guo  Constantin Christopoulos 《地震工程与结构动力学》2013,42(9):1321-1338

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Multi range spectral feature fitting for hyperspectral imagery in extracting oilseed rape planting area     

《International Journal of Applied Earth Observation and Geoinformation》2013

Spectral feature fitting (SFF) is a commonly used strategy for hyperspectral imagery analysis to discriminate ground targets. Compared to other image analysis techniques, SFF does not secure higher accuracy in extracting image information in all circumstances. Multi range spectral feature fitting (MRSFF) from ENVI software allows user to focus on those interesting spectral features to yield better performance. Thus spectral wavelength ranges and their corresponding weights must be determined. The purpose of this article is to demonstrate the performance of MRSFF in oilseed rape planting area extraction. A practical method for defining the weighted values, the variance coefficient weight method, was proposed to set up criterion. Oilseed rape field canopy spectra from the whole growth stage were collected prior to investigating its phenological varieties; oilseed rape endmember spectra were extracted from the Hyperion image as identifying samples to be used in analyzing the oilseed rape field. Wavelength range divisions were determined by the difference between field-measured spectra and image spectra, and image spectral variance coefficient weights for each wavelength range were calculated corresponding to field-measured spectra from the closest date. By using MRSFF, wavelength ranges were classified to characterize the target's spectral features without compromising spectral profile's entirety. The analysis was substantially successful in extracting oilseed rape planting areas (RMSE ≤ 0.06), and the RMSE histogram indicated a superior result compared to a conventional SFF. Accuracy assessment was based on the mapping result compared with spectral angle mapping (SAM) and the normalized difference vegetation index (NDVI). The MRSFF yielded a robust, convincible result and, therefore, may further the use of hyperspectral imagery in precision agriculture.  相似文献   

Hyperspectral discrimination of tree species with different classifications using single- and multiple-endmember     

《International Journal of Applied Earth Observation and Geoinformation》2013

Discrimination of tree species with different ages is performed in three classifications using hyperspectral data. The first classification is between Broadleaves and pines; the second classification is between Broadleaves, Corsican Pines, and Scots Pines, and the third classification is between six tree species including different ages of Corsican and Scots Pines. These three classifications are performed by having single- and multiple-endmember and considering five different spectral measure techniques (SMTs) in combination with reflectance spectra (ReflS), first and second derivative spectra. The result shows that using single-endmember, derivative spectra are not useful for a more challenging classification. This is further emphasized in multiple-endmember classification, where all SMTs perform better in ReflS rather than derivative in all classifications. Furthermore, using derivative spectra, discrimination accuracy become more dependent on the type of SMTs, especially in single-endmember. By employing multiple-endmember, the within-species variation is significantly reduced, thereby, the remaining challenge in discriminating tree species with different ages is only due to the between-species similarity. Overall, discrimination accuracies around 92.4, 76.8, and 71.5% are obtained using original reflectance and multiple-endmember for the first, second, and third classification, which is around 14.3, 17, and 8.3% higher than what were obtained in single-endmember classifications, respectively. Also, amongst the five SMTs, Euclidean distance (in both single- and multiple-endmember) and Jeffreys–Matusita distance (in single-endmember and derivative spectra) provided the highest discrimination accuracies in different classifications. Furthermore, when discrimination become more challenging from the first to second and third classification, the performance difference between different SMTs is increased from 1.4 to 3.8 and 7.3%, respectively. The study shows high potential of multiple-endmember to be employed in remote sensing applications in the future for improving tree species discrimination accuracy.  相似文献   

Satellite mapping of oolitic ridges in Arabs Gulf,Egypt     

L. Tommy Lindell  E. Torbjörn Alexandersson  John O. Norrman 《国际地球制图》2013,28(1):49-59

When the ecological effects of the proposed Qattara Hydrosolar Power Project were investigated, a number of submarine ridges were found in Arabs Gulf, Egypt.Those ridges were of unconsolidated oolitic origin, which was of critical importance for the water intake conditions of the Qattara Project. They were scientifically extremely interesting as being the first recent oolites ever found in the Mediterranean. The ridges have been studied concerning the geology, morphology and the water dynamics both in the field and from different satellite sensors‐MSS, TM and SPOT. Satellite mapping of the structure of the ridges, benthic algae and geology has been performed. The identification of the benthic algae has been accomplished by a semi‐manual box‐classifier technique.

A new accurate depth chart of Arabs Gulf has been constructed using TM data calibrated against echosoundings.

By creating a synthetical digital terrain model of the bed‐rock of Arabs Gulf and comparing it with the satellite image the amount of oolitic material of the bay has been estimated.

The character and location of the ridges has been compared with similar oolitic forms in the West Indies.  相似文献