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The inverse linear problem for large scale magnetic survey
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 16th International Conference on Geoinformatics - Theoretical and Applied Aspects, May 2017, Volume 2017, p.1 - 6
Abstract
A large-scale magnetic survey in 20×10 m grid nodes was carried out in a number of small iron ore deposits near the city of Krivoi Rog in the 1980s. The ore mining in the southern part of the Petrovsky deposit was started in 1973, and today it producted at depths of 100–110 m. Today detailed geological exploration work is carried out by drilling wells up to 300 m deep on several profiles. The ore deposit is very heterogeneous in iron content and is permeated with vein intrusions of granites. It was necessary to determine the most promising direction of further extraction. There was a need for a new interpretation of the magnetic survey data by more progressive methods with the separation of the ore body on horizontal layers 40–60 m thick. And the layers themselves must be divided into 25×25 m blocks. Today, it is possible to obtain stable solutions of inverse problems with the same parameters and the same dimension. But there are some difficulties. As is known, inverse problems of magnetometry are strongly uncorrect, in particular, because in many cases they give equivalent solutions and do not provide real information about geological structures. And on the other hand, on theoretical and real examples it is established that iterative methods in solutions of inverse problems for each block of the model give stable and geologically meaningful parameters. An iterative optimization method with a criterion for minimizing the sum of the squares of the corrections to the magnetization will give its most accurate distribution when the mean square error of the field will the smallest. This statement is used to detail the results of large-scale magnetic surveys.