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41.
Edgardo Cañón-Tapia 《Pure and Applied Geophysics》1994,142(2):365-382
Twenty-eight parameters used to characterize measurements of the anisotropy of magnetic susceptibility are compared theoretically in this work by introducing the concept of the field of susceptibility tensors, which allows the representation of parameters as families of lines in a plane. It is demonstrated that the foliation and lineation parameters are but a special case of the shape parameters, implying that the resolution of these two rock fabric elements using AMS measurements alone is more an artifact of the numerical range of definition of some parameters than a quantification of two physically independent features. Also, it is shown that parameters presumably of the same type do not necessarily yield equivalent interpretation of results in a qualitative sense, and therefore, caution should be strongly exercised when parameters are to be selected. Paramters quantifying the degree of anisotropy are, in general, equivalent to each other because of the very small departure observed in natural rocks from the isotropic case. However, a final consideration of the possible ability to differentiate rock types and a convenient range of values allowing expression of the degree of anisotropy in a well-defined percentage are pointed out as the main factors to be considered before selecting one parameter within this class. 相似文献
42.
43.
We present the results of the application of three-dimensional Hilbert transformation to the analysis of airborne total field magnetic anomalies over part of Southeastern Nigeria. This study not only substantiates the usefulness of 3-D Hilbert transforms in the interpretation of magnetic anomaly maps but also more clearly delineates the structural pattern of the area, of study. Results from the previous study are discussed in relation to the results of previous geological and geophysical studies of the area. 相似文献
44.
S. K. G. Krishnamacharyulu Bh. V. V. Gopalarao I. V. Radhakrishna Murthy 《Pure and Applied Geophysics》1990,132(4):719-731
Magnetic anomaly profiles over two thin sheets separated by a small distance resemble those of dykes andvice versa. Interpretation of anomalies over a pair of sheets based on the magnetic properties of dykes predicts a dyke whose centre lies midway between the positions of the sheets. The dyke, on the other hand, is magnetically equivalent to a pair of sheets, both lying at the same depth and having the same magnetization.The magnetic anomalies due to a pair of sheets can be interpreted by framing linear equations between the anomalies and their distances measured from an arbitrary reference. Application of this method to anomalies of dipping sheets with a finite depth extent is indicated. 相似文献
45.
本文数值研究了地球远磁尾中流动撕裂模不稳定性所引起的磁场重联过程.结果表明,在短暂的指数增长之后,当磁岛宽度接近等离子体片厚度时,流动撕裂模不稳定性的增长率大大降低,最终磁岛宽度趋于饱和.磁岛的饱和宽度随着磁Reynolds数S的增大而减小,随着剪切流动层宽度δV的增大而增加.在S→∞的情况下,流动撕裂模将退化为流动颈缩模,磁场重联不再发生.当飞船通过由流动撕裂模不稳定性所形成的磁岛时,即可观测到磁场B_z分量由北转南或由南转北的现象. 相似文献
46.
根据IGY/IGC期间全球地磁台网以及中国地磁台站的资料,计算出每-UT小时的Sq外源和内源电流体系.对Sq电流体系UT变化和经度效应的分析研究表明,Sq外源电流体系的空间图案没有显著的UT变化,电流涡焦点的地理纬度与磁赤道有密切关系,其变化范围,北半球为25°-35°N,南半球为30°-42.5°S.外源电流总强度的平均值为229kA(北半球)和173kA(南半球),其变化范围为±50kA(北半球)和±40kA(南半球).Sq内源电流体系的图案和强度有显著的UT变化,电流体系焦点纬度有类似于外源电流系的变化.在大西洋、印度洋、北太平洋地区,内源电流体系的总强度明显小于大陆地区的内源电流强度,表明这些大洋地区上地幔电导率低于大陆地区. 相似文献
47.
48.
本文证明任意阶次磁多极子场力线方程总可以用有限形式解析地表示,并对偶极族和四极族磁多极子场力线的位形给予注记。 相似文献
49.
A S Subrahmanyam K S R Murphy T C S Rao M M Malleswara Rao S Lakshminarayana K Venkateswarlu 《Journal of Earth System Science》1994,103(1):17-26
A detailed analysis of bathymetry and magnetic data of Visakhapatnam-Paradip shelf, east coast of India revealed three major
structural lineaments over the shelf/slope of the area. Models derived from the anomalies associated with the trends indicate
that trend A represents horst and graben type continental basement while trend B is due to a series of dyke intrusions. Trend
C off Chilka lake forms the northward extension of 85°E lineation from deep sea Bengal Fan.
A two stage evolution of the eastern continental margin of India has been inferred from the study of this part of the margin,
viz., the rift stage evidenced by dyke intrusions of reverse polarity located within the inner part of the shelf and post-rift
stage characterized by vertical tectonics in the form of a horst and graben type continental basement. The hotspot related
aseismic 85°E ridge further complicated the tectonics of this part of the area. 相似文献
50.