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Post by raghusuribhatla on Jan 25, 2018 12:45:31 GMT -5
What are the limitations associated with using 2D forward and inverse models for imaging objects/features with limited depth (in the direction perpendicular to the surveyed/modeled section).
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Post by alainplattner on Jan 25, 2018 14:09:30 GMT -5
If your subsurface resistivity structure is perpendicular to your profile, then two-dimensional investigations (using a 2.5-D modeling approach) should do fine. If your resistivity structure is not perpendicular to the profile, then you can expect to get significant artifacts which may be difficult to interpret. For example, when you are mapping an elongated contrast that is striking your profile at an oblique angle, you will see "pant leg" artifacts. When the contrast is only present on one side of the profile and at some distance, your two-dimensional image will show it at a greater depth. An undergrad student and I have a research paper which is currently under review by the Journal of Applied Geophysics. The title is "Offset-electrode profile acquisition strategy for electrical resistivity tomography". In it we show these two examples of artifacts and we propose a way to avoid them: Shift your electrodes away from the profile in an alternating manner (like a zigzag pattern following the profile) and then use 3D inversion software (there are free software packages available like for example BERT: anaconda.org/gimli/pybert see www.pygimli.org/ for installation instructions or E4D: e4d.pnnl.gov/). In our paper we show that this approach avoids such artifacts and is easy to use in the field. |
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