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991.
S. Balachandar 《Geophysical Journal International》1998,132(1):111-127
The two-point correlation tensor provides complete information on mantle convection accurate up to second-order statistics. Unfortunately, the two-point spatial correlation tensor is in general a data-intensive quantity. In the case of mantle convection, a simplified representation of the two-point spatial correlation tensor can be obtained by using spherical symmetry. The two-point correlation can be expressed in terms of a planar correlation tensor, which reduces the correlation's dependence to only three independent variables: the radial locations of the two points and their angular separation. The eigendecomposition of the planar correlation tensor provides a rational methodology for further representing the second-order statistics contained within the two-point correlation in a compact manner. As an illustration, results on the planar correlation are presented for the thermal anomaly obtained from the tomographic model of Su, Woodward & Dziewonski (1994 ) and the corresponding velocity field obtained from a simple constant-viscosity convection model Zhang & Christensen 1993 ). The first 10 most energetic eigensolutions of the planar correlation, which constitute an almost three orders of magnitude reduction in the data, capture the two-point correlation to 97 per cent accuracy. Furthermore, the energetic eigenfunctions efficiently characterize the thermal and flow structures of the mantle. The signature of the transition zone is clearly evident in the most energetic temperature eigenfunction, which clearly shows a reversal of thermal fluctuations at a depth of around 830 km. In addition, a local peak in the thermal fluctuations can be observed around a depth of 600 km. In contrast, due to the simplicity of the convection model employed, the velocity eigenfunctions exhibit a simple cellular structure that extends over the entire depth of the mantle and do not exhibit transition-zone signatures. 相似文献
992.
准噶尔盆地砂岩储集岩生物标志化合物特征及其意义 总被引:4,自引:3,他引:4
油气储集岩(砂岩)粒间孔隙中自由状态的油气组分,与各种矿物相互吸附、结合(束缚状态)的油气组分,以及矿物内部的油气包裹体之间常规生物标志化合物组成(甾、萜烷分布)存在明显的差异。反映了不同成藏阶段油气组分的地球化学特征。展示了油气藏油气注入过程。为油源对比提供了新方法。 相似文献
993.
樊钧 《水文地质工程地质》1997,24(6):48-49
随着城市建设的迅速发展,勘测单位计算机应用已从孤立地处理单项工程走向管理和决策,以大型关系数据库为核心的信息管理和决策支持已经成为大型勘测单位设计地质信息系统的新命题。本文介绍了地质信息系统的特点及大型关系数据库在城市地质信息系统中的地位和作用。 相似文献
994.
995.
李应平 《地震学报(英文版)》1996,9(3):377-387
Microearthquakeanalysisforhydraulicfrac┐turingprocesYING-PINGLI(李应平)DepartmentofEarth,AtmosphericandPlanetarySciences,Masach... 相似文献
996.
Empirical site response evaluations: case studies in Israel 总被引:1,自引:0,他引:1
Y. Gitterman Y. Zaslavsky A. Shapira V. Shtivelman 《Soil Dynamics and Earthquake Engineering》1996,15(7):447-463
A closed-loop, time-efficient technique for site effect evaluation for seismic microzonation in urban areas is developed and implemented. It includes the following successive steps: microtremor measurements using a triangular array of three-component seismometers; estimation of the Nakamura horizontal-vertical spectral ratio, calculation of Rayleigh wave dispersion using the Aki spatial correlation method; inversion of the dispersion curve to determine a shear wave velocity model of the shallow subsurface; analytical computation of Rayleigh wave spectral ellipticity and 1-D SH transfer function for this model; and a comparison of empirical and analytical ratios and correction of the model if required. The technique has been tested at several locations in a number of towns near the active Jordan Rift valley. A reasonable agreement is obtained when comparing empirical spectral ratios and analytical transfer functions. 相似文献
997.
当利用自然电位法(SP法)在火山岩地区勘探地下水时,发现负的自电异常大小与地下非饱和区厚度之间存在一个线性关系,从理论上对该经验关系进行了探讨,并提出对这一水文地质问题的自电测量解释方法,最后给出法国中央高原LaChainedesPuys地区的勘探结果。 相似文献
998.
坠石是沉积时落入水体底部沉积物中的单个或集群状外来碎屑,按其搬运载体不同可分为:(1)冰筏成因坠石:冰山作用形成的坠石和季节性冰体形成的坠石;(2)非冰筏成因坠石;动物植成因坠石和其它成因坠石。坠石是寒冷气候的标志,其形成时的气候具有多解性。 相似文献
999.
福建省地层多重划分,对比研究(续) 总被引:1,自引:0,他引:1
福建省地层多重划分、对比研究(续)李兼海,王国平,郑铁藩,梁诗经(福建省区域地质调查队,三明,365001)3晚三叠世一新第三纪印支运动后,福建地壳发生了重大变革,全境由海转变成陆地。晚三叠世一中佛罗世,除闽西南局部地区有海湾泻湖相沉积外,皆为河流一... 相似文献
1000.
Thierry Adatte Wolfgang Stinnesbeck Jürgen Remane Hans Hubberten 《Cretaceous Research》1996,17(6):671-689
Mexico is usually considered to have formed the western end of the Tethys during Late Jurassic and Early Cretaceous times. The circumstances of the opening of the Gulf of Mexico Basin towards the Tethys and the exact stratigraphic timing, however, are not clear. Four sections covering this time interval, located in northeastern Mexico, have been measured and sampled in detail, in order to clarify their stratigraphic position during the Late Jurassic to Early Cretaceous time interval and the paleogeographic and oceanographic changes that accompanied this opening. Our studies include microfacies, micro- and macropaleontology, whole rock and clay-mineral x-ray diffraction and stable isotopes analyses. Our data indicate that the Jurassic-Cretaceous boundary, as defined by the Lyon-Neuchâtel Colloquium of 1973, cannot be determined precisely in northeastern Mexico due to the near-absence of calpionellids and endemism of ammonite taxa. In the lower and upper Berriasian sediments, we detected Mediterranean ammonite taxa so far unknown from Mexico, corresponding to the appearance of typical calpionellid-rich facies. These faunas allow direct biostratigraphic correlation with European ammonite and calpionellid zones.We propose that a major oceanographic change occurred in the upper part of calpionellid Zone B of the Early Berriasian. At this time, sediments in northeastern Mexico present increasingly pelagic facies, a dramatic appearance of Tethyan microfossils (calpionellids) and ammonites, changes in stable isotopic values, whole rock and clay-mineral mineralogy. We suggest that these changes are due to a global sea-level rise that connected directly northeastern Mexico to the European Tethys and ended the endemic, semi-restricted and anoxic environment of the Late Jurassic La Casita and equivalent La Caja and La Pimienta Formations. 相似文献