Island geomagnetic observatories and upper mantle electric conductivity profiles

冰岛地磁观测站和上地幔电导率剖面

• 批准号: 321788553
• 负责人: Dr. Achim Morschhauser
• 金额: --
• 依托单位: Institut für Geophysik
• 依托单位国家: 德国
• 项目类别: Research Fellowships
• 财政年份: 2016
• 资助国家: 德国
• 起止时间: 2015-12-31 至 2016-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/321788553?language=en
• 关键词: Island; geomagnetic; observatories; upper; mantle

The electrical conductivity profile of the Earth can be investigated by analyzing the observed magnetic and electric fields at the surface. Observations of the geomagnetic field are readily available from a worldwide network of ground-based geomagnetic observatories which provide data of high quality and of high resolution. However, simultaneous electric field measurements of comparable quality and quantity are not provided. Recently, a method to obtain 1-D electric conductivity profiles from geomagnetic observations alone has been suggested. This method is based on the observation of tippers, which relate the vertical and horizontal components of the observed geomagnetic field variations. Further, this method has been demonstrated to resolve 1-D conductivity profiles of the crust and upper mantle by exploiting the known lateral conductivity contrasts of seawater and bedrock near island observatories. With other methods, such conductivity profiles are difficult to obtain due to the logistical challenges associated with observations at sea.In this project, we will apply the recently suggested method to island observatories. For this purpose, we will select suitable observatories, calculate tippers from the geomagnetic data, and assemble detailed models of the island bathymetry. Finally, we will invert these tippers for local 1-D conductivity profiles of the crust and upper mantle. Such conductivity profiles contain valuable information on chemical and thermal transport properties, but also will help to improve our understanding of the measured surface magnetic field which results from a variety of sources. These sources are difficult to separate, and this research project will help to extract the signal of the induced sources in the upper mantle. In consequence, this research project may as well contribute to our knowledge of the electric current systems in the ionosphere and magnetosphere and facilitate the joint interpretation of satellite and ground based geomagnetic observations.

通过对地表观测到的磁场和电场的分析，可以研究地球的电导率分布。通过提供高质量和高分辨率数据的全球地面地磁观测站网络，随时可以获得对地磁场的观测。然而，没有提供质量和数量相当的同时电场测量。最近，有人提出了一种仅从地磁观测获得一维电导率剖面的方法。这种方法是基于对翻斗车的观测，它将观测到的地磁场变化的垂直和水平分量联系起来。此外，这种方法已被证明通过利用岛屿附近观测站附近海水和基岩的已知横向电导率对比来解算地壳和上地幔的一维电导率剖面。对于其他方法，由于与海洋观测相关的后勤挑战，这样的电导率剖面很难获得。在这个项目中，我们将把最近建议的方法应用到岛屿天文台。为此，我们将选择合适的观测站，根据地磁数据计算倾斜率，并组装岛屿水深测量的详细模型。最后，我们将对这些倾斜仪进行地壳和上地幔局部一维电导率剖面的反演。这种电导率分布包含有关化学和热传输性质的有价值的信息，但也将有助于我们更好地理解由各种来源产生的测量表面磁场。这些源很难分离，这一研究项目将有助于提取上地幔诱发源的信号。因此，这一研究项目也可能有助于我们了解电离层和磁层中的电流系统，并促进对卫星和地面地磁观测的联合解释。