Correction of seafloor magnetotelluric data for topographic effects during inversion
Correction of seafloor magnetotelluric data for topographic effects during inversion
复制标题
反演期间地形效应海底大地电磁数据的校正
DOI：
10.1029/2004jb003463
复制
发表时间：
2005
影响因子：
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通讯作者：
A. Chave
中科院分区：
文献类型：
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作者：
K. Baba;A. Chave
[1] 海水与海底之间电导率的巨大差异会积累边界电荷，从而严重扭曲观测到的电场和磁场。对于海洋大地电磁 (MT) 研究，纠正这种地形效应对于获得准确的地幔电导率模型至关重要。以前，地形校正是基于薄片近似，该近似在深海中的周期小于 1000 秒时就会失效。本文介绍了一种海底大地电磁数据分析方法，该方法结合了去除三维（3-D）地形影响和反演数据的二维结构。首先使用观测到的水深测量将观测到的 MT 阻抗校正为平坦的海底基准，而不调用薄片近似。然后将校正后的 MT 响应在平坦的海底模型空间中进行反演。由于地形效应和更深层次结构之间的耦合，校正和反演步骤会被迭代，直到每个步骤的变化变小。该程序使用合成数据和真实数据进行验证。对半空间上的合成 3-D 形貌的测试表明，该方法在几次迭代后可以很好地恢复真实的半空间模型。该程序还适用于在南纬 17° 东太平洋海隆的地幔电磁和断层扫描 (MELT) 实验中收集的真实数据。
[1] The large contrast in electrical conductivity between seawater and the underlying seafloor accumulates boundary electric charges which can severely distort observed electric and magnetic fields. For marine magnetotelluric (MT) studies, correcting this topographic effect is critical to obtaining accurate conductivity models for the mantle. Previously, correction for topography was based on the thin sheet approximation which breaks down at periods under ∼1000 s in the deep ocean. This paper introduces an analysis method for seafloor MT data which combines removal of three-dimensional (3-D) topographic effects with inversion of the data for 2-D structure. The observed MT impedance is first corrected to a flat-lying seafloor datum using the observed bathymetry without invoking the thin sheet approximation. The corrected MT response is then inverted in a flat seafloor model space. Because of coupling between topographic effects and deeper structure, the correction and inversion steps are iterated until changes in each become small. The procedure is verified using synthetic and real data. Tests for synthetic 3-D topography over a half-space show that the method closely recovers the true half-space model after a few iterations. The procedure is also applied to real data collected in the Mantle Electromagnetic and Tomography (MELT) experiment on the East Pacific Rise at 17°S.
H.264编码器DCT的硬件实现及其评估
DOI：
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发表时间：
2009
期刊：
影响因子：
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作者：
Choong Geun Lee;V. G. Moshnyaga and K. Hashimoto;宮田康治
通讯作者：
宮田康治