Inversion Constraints

GM-SYS 3D allows the use of “constraints” grids to constrain or restrict some of the inversion options. A “constraints” grid is a grid that matches the “index” grid for the model and contains values between 0 and 1. Where the value of a grid node in the constraints grid is set to 0, the corresponding location in the grid being inverted will remain unchanged. Where the value of a grid node in the constraints grid is set to 1, the corresponding location in the grid being inverted is totally unconstrained. If the value in the constraints grid is greater than 0 and less than 1, it acts as a weighting factor to slow down the amount of movement during inversion. There are four tools for creating a constraints grid in the “Grid Editing” menu.

For example, if you are inverting on depth to basement in an area surrounded by outcropping basement, you might build a constraints grid that is set to 0 in the areas of basement outcrop and 1 in the center of the basin. The transition from 0 to 1 would determine how sharply the edges of the basin could drop off.