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Aviation Transient Electromagnetic Method Of One-dimensional Forward Modeling And Inversion Interpretation

Posted on:2011-11-21Degree:MasterType:Thesis
Country:ChinaCandidate:Y X LiFull Text:PDF
GTID:2190360305994110Subject:Earth Exploration and Information Technology
Abstract/Summary:PDF Full Text Request
Airborne transient electromagnetic (ATEM), with its high efficiency and low cost, could be widely applied in fields such as geological mapping, direct or indirect mineral prospecting, hydrological investigation, environmental exploration and so on. With the national attention in recent years, ATEM has been developed rapidly.In this paper, the 1-D ATEM forward modeling and interpretation method are studied. Firstly, the 1-D forward modeling formula of dipole-dipole array is derived from the electromagnetic field expression of a magnetic dipole source above the layered earth, and the algorithm is optimized with new achievements in mathematics. The program is made up, and the features of ATEM exploration method are studied by analysing the responses of layered earth models with different array types, array parameters and model parameters.All the ATEM data interpretation methods are studied systematically, and classified into approximation interpretation techniques and quantitative inversion methods. For the former, this paper presents two techniques:all-time apparent resistivity abtained by iteration method and one of the conductivity-depth transformation (CDT) methods:S-inversion. For the latter, there are also two methods presented:the Occam inversion method by which a smoothest model could be generated, and the alternate model adjustment method whose results could interpret the data with high precision.By the studies above, the following conclusions can be acquired:1) The forward modeling shows that the signal of the horizontal parallel array is stronger than any other array, and that is why this kind is more adoptive in application; the anomaly induced by conductance is much more powerful than the one by resistance.2) Approximation interpretation techniques are suitable for immediate interpretation for mass field data due to its fast processing speed, while, the quantitative inversion methods which give better results with lower efficiency can be used in later data processing and analysis.3) The results of the S-inversion method reflect the conductance anomaly obviously, and in whose profile, the depth where resistivity drops most sharply can be considered as the top of conductance layer. 4) Occam inversion method, which generate a smoothest model, is suitable electromagnetic exploration, and its stability is demonstrated by model experiments; the alternate model adjustment method is developed by experiential skill, and the examples prove its higher precision and better results.
Keywords/Search Tags:Airborne transient electromagnetic (ATEM), 1-D forward modeling, all time apparent resistivity, floating sheet method, Occam inversion, alternate model adjustment method
PDF Full Text Request
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