
TY  - JOUR
A1  - Yang, Dikun 
A1  - W. Oldenburg, Douglas 
T1  - Practical 3D inversion of large airborne time domain electromagnetic data sets
JF  - ASEG Extended Abstracts
JO  - ASEG Extended Abstracts
Y1  - 2012
VL  - 2012
IS  - 1
SP  - 1
EP  - 4
KW  - 
UR  - https://doi.org/10.1071/ASEG2012AB173 
N2  - In this paper we show that 3D inversion of large airborne time domain EM data, which is traditionally considered impractical, can be rapidly carried out by using a thoughtful workflow. In our 3D inversion algorithm, the number of cells in the mesh and the number of soundings are two factors that slow down the inversion. Therefore, we develop a strategy of adaptive mesh and sounding refinement to minimize the number of cells and the number of soundings required by the inversion. At the beginning, a coarse mesh and a few soundings are used to quickly build up a large-scale model. Then the mesh is refined and more soundings are added based upon their data misfit. At each iteration of the inversion, a certain number of soundings are randomly selected, and we change the data selection from iteration to iteration. This allows us to down-sample the field data without much loss of information. Once the large-scale model is obtained, we carry out some tile inversions that focus on smaller areas with a locally refined mesh to better resolve the small-scale features. The workflow is demonstrated by a synthetic example with 2121 transmitters that takes about 10 hours to be solved compared to about 150 hours if we had started the inversion on a fine mesh and used all of the transmitters. The methodology of speeding up the inversion by adaptive mesh and data refinement can also be applied to other EM surveys. 
ER  -

