Modelling and inversion of geophysical electromagnetic data

地球物理电磁数据建模与反演

• 批准号: 326988-2007
• 负责人: Farquharson, Colin
• 金额: $ 1.2万
• 依托单位: Memorial University of Newfoundland
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2009
• 资助国家: 加拿大
• 起止时间: 2009-01-01 至 2010-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=428603
• 关键词: Modelling; inversion; geophysical; electromagnetic; data

The goal of geophysics is to understand, and perhaps predict, the dynamic processes that move and shape the Earth beneath our feet, and to "look" into the Earth to see these processes in action, or their consequences. One technique for remotely sensing what the structure of the subsurface is, even to depths of tens of kilometres, uses electromagnetic fields. In this technique, electric currents are induced to flow in the rocks. The strength and disposition of the currents depend on rock type. Metallic ores, for example, are relatively good at conducting electricity. The induced currents in the ground give rise, in turn, to electromagnetic fields which can be measured. The strengths and variations of these measurements depend on the induced currents, and so on the rocks themselves. It is therefore possible to turn the measurements on their heads, that is, invert them, and extract information about what the rock types are in the subsurface. The proposed research determines to (i) improve the mathematics used by computer programs to predict what the induced currents would be if the rock types in the subsurface were known, and (ii) improve the programs that invert measurements of the electromagnetic fields to generate models of the structure of the Earth. Recent advances have produced what is effectively the first generation of these programs for fully three-dimensional models of the Earth. However, the mathematical representations these programs use for the arrangements of rock types in the subsurface are basic, being neither flexible enough to cope with the complicated structures that occur in nature, nor precise enough to handle the dramatic changes between adjacent rock types that can exist for certain important features such as ore deposits. This research programme will investigate the use of more sophisticated and refined representations of the subsurface to overcome these problems. The result will be computer programs that can provide more detailed and more reliable models, or "images", of the subsurface. These programs will be of use to the mining industry, enabling new ore deposits to be found. They will also be of use in remotely sensing groundwater resources, geotechnical applications, and in determining the deep structure of the Earth's crust.

地球物理学的目标是理解，也许是预测，移动和塑造我们脚下的地球的动态过程，并“看”到地球看到这些过程的行动，或其后果。一种遥感地下结构的技术，甚至是几十公里深的地下结构，就是利用电磁场。在这项技术中，电流被诱导在岩石中流动。水流的强度和分布取决于岩石类型。例如，金属矿石的导电性相对较好。大地中的感应电流又产生可测量的电磁场。这些测量的强度和变化取决于感应电流，以及岩石本身。因此，有可能将测量结果颠倒过来，也就是说，将它们颠倒过来，并提取关于地下岩石类型的信息。拟议的研究确定（i）改进计算机程序使用的数学，以预测如果地下岩石类型已知，感应电流会是什么，以及（ii）改进反演电磁场测量的程序，以生成地球结构的模型。最近的进展已经产生了什么是有效的第一代这些程序的全三维模型的地球。然而，这些程序用于地下岩石类型排列的数学表示是基本的，既不足够灵活以科普自然界中发生的复杂结构，也不足够精确以处理相邻岩石类型之间的剧烈变化，这些岩石类型可能存在某些重要特征，如矿床。这项研究计划将调查使用更复杂和更精细的地下表示来克服这些问题。其结果将是计算机程序，可以提供更详细和更可靠的模型，或“图像”，地下。这些程序将用于采矿业，使新的矿床被发现，它们也将用于遥感地下水资源，岩土工程应用，并在确定地壳的深层结构。