Working with Faulted Surfaces

Here are some suggestions for possible workflows in applying faults to surfaces in RockWorks.  These instructions assume you don’t have the coordinates for your faults already defined in an external spreadsheet or in the RockWorks project database; you can draw the fault lines on a map and then use them to fault a surface.

1. Create your contour map in RockWorks without faulting turned on.

  • Use the Utilities Map | Grid-Based Map if your XYZ data is entered into the Utilities datasheet.
  • Use any of the Borehole Manager contour mapping options (Map | Borehole Locations for ground surface contours, Stratigraphy | Structural Elevations for stratigraphic structure maps, etc.) if your data is entered into the borehole database.
RockWorks Unfaulted Contour Map
Unfaulted structure contour map

2. In the displayed map, use the Draw | Line Types | Polyline to draw a fault polyline on your map.  Double-click to terminate the polyline.  You can repeat this if you have multiple faults.

RockWorks unfaulted contour map with drawn polyline

Unfaulted contour map with drawn polyline

3. Choose the arrow-shaped Edit tool from the RockPlot2D toolbar, and click on the polyline you drew, to select it.  (If selected, you’ll see square icons on the vertices.)  If you have multiple polylines drawn, hold down the Shift key on your keyboard to click on the next polyline to select it as well.  Continue in this manner for as many polylines as you drew so that all are selected.

4. Right-click on any of the selected polylines in the map window and choose Save to Faults Table.

Save Fault Polyline to a "Faults Table"

Save Fault Polyline to a "Faults Table"

Enter a name to assign to the Faults Table and click OK.  This will be saved to the project database.

5. Return to the options along the left side of the map window, and click on the Gridding Options button.  Here, turn on the Faulting option (which is available under Inverse-Distance).  Enter the “distance multiplier” (usually 10) and browse for the name of the Fault Table that you just created.

RockWorks Gridding Options - Faulting settings

Gridding Options - Faulting settings

Click OK to close this window. Click on the Grid Name prompt and enter a new name for the faulted grid model (such as “Potosi_faulted.grd”).

6. Click Process to recreate the grid model and map, now applying faulting.

RockWorks Faulted Contour Map

Faulted Contour Map

Here are three-dimensional views of these surfaces:

RockWorks - Unfaulted Surface in 3D

Unfaulted Surface in 3D

RockWorks - Faulted Surface in 3D

Faulted Surface in 3D

RockWorks applies faulting by creating an interpolation barrier on either side of the polyline(s) – as it’s interpolating a grid node, any control points on the other side of the fault are now considered to be 10 times further away than they actually are, thus having no influence on that node.

 

2 thoughts on “Working with Faulted Surfaces

  1. Nice, but I still have a question.
    If you are not happy with Inverse distance surface results and you prefare triangulation gridding, how can you apply faults to this surface?

    • Faulting is not available with the triangulation gridding method. You might have better results with the Inverse-Distance algorithm by reducing the number of neighbors which are used (from 8 to, say, 3) – might help avoid the bull’s-eyes.