Theory for magnetotelluric observations on the surface of a layered anisotropic half space
Theory for magnetotelluric observations on the surface of a layered anisotropic half space
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DOI：
10.1111/j.1365-246x.1973.tb02422.x
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发表时间：
2009-09
影响因子：
2.8
通讯作者：
D. Loewenthal;M. Landisman
中科院分区：
文献类型：
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作者：
D. Loewenthal;M. Landisman
总结一个大地电磁模型被认为是由一个垂直的圆柱体组成的水平层，每个具有横向和垂直均匀的导电性。因此，在以观测点为中心的垂直圆柱体内，磁、电和电流矢量场没有横向变化。层的电导率可以是各向同性的，对称各向异性的，或不对称各向异性的任意垂直顺序，与水平各向异性取向在任何方位角的垂直轴。层状半空间中阻抗张量的固有性质允许张量通过层传播，而无需像以前的工作那样计算相关的电场和磁场矢量。由此产生的新算法允许计算进行二阶矩阵，而不是四阶以前所需的，在速度和精度有相当大的提高。对其中一些模型的计算表明，需要进行跨越足够广泛时期的观测。计算结果，当考虑在一个狭窄的带宽，显示出极大地类似于那些完全不相似的模型。新的算法也被用于向下传播的阻抗张量在观测表面，使它有可能恢复电导率的垂直分布在有利的情况下。
Summary A magnetotelluric model is considered which consists of a vertical cylinder comprised of horizontal layers, each having a conductivity that is homogeneous both laterally and vertically. There are thus no lateral variations in the magnetic, electric, and current vector fields within the vertical cylinder centered about the observation site. The layer conductivities may be either isotropic, symmetrically anisotropic, or asymmetrically anisotropic in arbitrary vertical sequence, with the horizontal anisotropies oriented at any azimuth about the vertical axis. The intrinsic properties of the impedance tensor in the layered half space permit the tensor to be propagated through the layers without resort to the calculation of the associated electric and magnetic field vectors, as in previous works. The resulting new algorithm permits the calculation to be performed with second rank matrices instead of fourth rank as previously required, with a considerable improvement in speed and accuracy. The calculation of a number of these models illustrates the need for observations that span a sufficiently broad range of periods. Computed results, when considered over a narrow bandwidth, are shown to greatly resemble those for completely dis-similar models. The new algorithm is also used for downward propagation of the impedance tensor at the observational surface, so that it is possible to recover the vertical distribution of conductivity under favourable circumstances.