Previously, we looked at how to model a 2D fault in GEOVIA Minex, which is typically used when there is little to no information about the fault and the fault is assumed to be dipping vertically. 2D faulting is also preferred when modeling needs to be completed quickly. In contrast, 3D faulting is favored when detailed information is known about the fault, such as dip and throw.

In today’s post, we’ll be looking at 3D faulting and how to apply this functionality in your daily workflow. The below image is an example of a 3D fault model:

Firstly, ensure that:

• GEOVIA Minex 6.5.1 software is installed and running on your computer
• The Minex borehole database file (*.b31), geometry file (*.GM3) and parameter file (*.mpf) is open
• The borehole database file (*.b31) should already contain data that has been validated (e.g. no overlapping intervals, negative seam thicknesses etc)
• You have created DDNames or grid folders. For example UNFAULT.grd, REFAULT.grd.

Now, let’s begin with Creating a Fault Trace.

1. The first step in 3D faulting is to create a string that defines the fault trace by selecting String > Create.
   
   
   
2. Remember that a 3D fault can have variable dip and throw along the fault plane, therefore the string should be digitized at the fault’s true 3D location (e.g. where the fault outcrops on topography). For this reason, it is best to digitize the fault trace in Plan View and snap to data, where appropriate. There is only one string type to model a 3D fault, therefore choose Fault 3D under String Type.

   
   

3. After digitizing the fault trace, we recommend annotating the string with Direction Arrows, which will be useful later, with dip/throw assignment. Fault strings should not cross, please refer to the Minex help guide for more information on intersecting faults.

   

4. If you are planning to use a fault surface in conjunction with your fault string, then the fault string should match the triangulated fault surface. This is optional – for use with a variably dipping fault plane. See the below example:
   Note that if the string does not match the triangulated fault surface, 3D faulting will not work. To drape a string onto a triangulation, use String > Fit to > Triangle.
   

   Now that you have completed fault tracing, the next step is Fault Definition. We’ll be covering this in our next blog post, Part 2: How to Model a 3D Fault in GEOVIA Minex, but in the meantime check out our previous post on 2D fault modeling.