3D inversion of airborne electromagnetic data

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Publication Type pre-print
School or College College of Mines & Earth Sciences
Department Geology & Geophysics
Creator Zhdanov, Michael
Other Author Cox, Leif H.; Wilson, Glenn A.
Title 3D inversion of airborne electromagnetic data
Date 2012-01-01
Description Time-domain airborne surveys gather hundreds of thousands of multichannel, multicomponent samples. The volume of data and other complications have made 1D inversions and transforms the only viable method to interpret these data, in spite of their limitations. We have developed a practical methodology to perform full 3D inversions of entire time- or frequency-domain airborne electromagnetic (AEM) surveys. Our methodology is based on the concept of a moving footprint that reduces the computation requirements by several orders of magnitude. The 3D AEM responses and sensitivities are computed using a frequency-domain total field integral equation technique. For time-domain AEM responses and sensitivities, the frequency-domain responses and sensitivities are transformed to the time domain via a cosine transform and convolution with the system waveform. We demonstrate the efficiency of our methodology with a model study relevant to the Abitibi greenstone belt and a case study from the Reid-Mahaffy test site in Ontario, Canada, which provided an excellent practical opportunity to compare 3D inversions for different AEM systems. In particular, we compared 3D inversions of VTEM-35 (time-domain helicopter), MEGATEM II (time-domain fixed-wing), and DIGHEM (frequency-domain helicopter) data. Our comparison showed that each system is able to image the conductive overburden and to varying degrees, detect and delineate the bedrock conductors, and, as expected, that the DIGHEM system best resolved the conductive overburden, whereas the time-domain systems most clearly delineated the bedrock conductors. Our comparisons of the helicopter and fixed-wing time-domain systems revealed that the often-cited disadvantages of a fixed-wing system (i.e., response asymmetry) are not inherent in the system, but rather reflect a limitation of the 1D interpretation methods used to date.
Type Text
Publisher Society of Exploration Geophysicists
Volume 77
Issue 4
First Page WB59
Last Page WB69
Dissertation Institution University of Utah
Language eng
Bibliographic Citation Cox, L. H., Wilson, G. A., & Zhdanov, M. S. (2012). 3D inversion of airborne electromagnetic data. Geophysics, 77(4), WB59-WB69.
Rights Management (c)Society of Exploration Geophysicists
Format Medium application/pdf
Format Extent 3,794,734 bytes
Identifier uspace,17686
ARK ark:/87278/s6708k6f
Setname ir_uspace
Date Created 2012-08-29
Date Modified 2012-09-07
ID 708072
Reference URL https://collections.lib.utah.edu/ark:/87278/s6708k6f
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