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- ISSN: 0812-3985
- E-ISSN: 1834-7533
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Using the in-line component for fixed-wing EM 1D inversion
- Australian Society of Exploration Geophysicists
- Source: Exploration Geophysics, Volume 46, Issue 6th International Conference in Airborne Electromagnetics (AEM 2013), Mar 2015, p. 130 - 135
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- 19 Mar 2014
- 30 Jun 2014
- 01 Mar 2015
Abstract
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Numerous authors have discussed the utility of multicomponent measurements. Generally speaking, for a vertical-oriented dipole source, the measured vertical component couples to horizontal planar bodies while the horizontal in-line component couples best to vertical planar targets. For layered-earth cases, helicopter EM systems have little or no in-line component response and as a result much of the in-line signal is due to receiver coil rotation and appears as noise. In contrast to this, the in-line component of a fixed-wing airborne electromagnetic (AEM) system with large transmitter–receiver offset can be substantial, exceeding the vertical component in conductive areas. This paper compares the in-line and vertical response of a fixed-wing airborne electromagnetic (AEM) system using a half-space model and calculates sensitivity functions. The a posteriori inversion model parameter uncertainty matrix is calculated for a bathymetry model (conductive layer over more resistive half-space) for two inversion cases; use of vertical component alone is compared to joint inversion of vertical and in-line components. The joint inversion is able to better resolve model parameters. An example is then provided using field data from a bathymetry survey to compare the joint inversion to vertical component only inversion. For each inversion set, the difference between the inverted water depth and ship-measured bathymetry is calculated. The result is in general agreement with that expected from the a posteriori inversion model parameter uncertainty calculation.
,In conductive areas, the in-line component of an offset transmitter–receiver EM system can be more sensitive to the near-surface than the vertical component. Using estimated noise levels, this paper calculates the expected uncertainty on the inverted parameters of a bathymetry model and compares this to inversion results from field data.
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ASEG