How to: Run an inversion in GMSYS-2D
Symptom/Problem:
User would like to invert their data in GMSYS-2D.
Environment:
Oasis Montaj, licensed for GMSYS-2D Intermediate level and higher.
Resolution:
Inverting requires that you have observed data as well as a calculated gravity and\or magnetic response in your model. A block model has also been constructed as a pre-requisite.
Inversion will re-compute the calculated model response to match the observed data by using free parameters that you set. In the example below, the user is inverting on density only.
- Click on INV on the Action toolbox.
- On the Inversion Setup box, select Density under Free\Fix.
Now click on all blocks for which you wish to free up for the parameter - density. - As you click (once), you will see a small "D" appear by the block's label.
Click the same block again to remove the "D" which sets the block back to fixed density again.
- Clicking Auto DC Level will enable the DC offset between observed and calculated response to vary as well.
- Click G:M to adjust the Gravity Ratio.
Gravity Ratio is applicable when you invert using magnetic parameters as well. A ratio of 1.0 indicates only the gravity model is used in the inversion.
0.5 indicates an equal bias is applied to inverting gravity and magnetic parameters
- Click GO when all required densities are set to vary
- As you click (once), you will see a small "D" appear by the block's label.
You can invert on other properties in a similar fashion, (X, Z, XZ (x and z offset freed up), susceptibility). The inversion then becomes joint optimisation.
Further instruction is available in the GMSYS User's Guide.
