How to Model a Fault in Surpac

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The GEOVIA Surpac™ fault modeling menu is a simple and efficient method of creating surfaces where only one edge has been observed in the field. This could be the trace of a fault from a geological map or a cross section line. This function is also useful if you would like to georegister a scanned cross section or geophysical profile in Surpac. After the DTM has been created, you can use the function file>images>drape an image file over a DTM.

There are various ways to model a fault in Surpac:

  • Using a digitized fault trace (the fault modeling menu)
  • From a single survey point. (the fault modeling menu)
  • By digitizing the extents/trace of the fault plane and using one of the triangulation functions (the manual method).

Today, we’ll discuss using a digitized fault trace.

You can digitize a fault trace manually, from surveyed point coordinates, by bearing and distance from existing points or on top of a draped image. The string does not need to be draped on top of the surface, as the fault function can project the surface in two directions.

Once you have a fault trace, you may choose to use a single dip and dip direction for the whole fault, or changing values for a twisted surface. If you would like to enter changing values along the trace, here there are various methods:

1. Use the function edit>point>maths. This will allow you to enter the description field values as below. In the image, below, the d1 field will contain the dip angle in degrees (negative values mean below horizontal), and the d2 field will contain the dip direction in degrees (not the strike). Once you select “apply”, you will be able to graphically select the points you would like these values to be added to. The function will allow you to click points in succession until you select Esc on your keyboard.

2. If you would like to set every point in the segment to the same description field values, enter the values into the fault modeling menu.

You are now ready to use the fault triangulation function. Go to surfaces>fault modeling>generate fault from trace. You will be asked to define:

  • If the fault is generated from a segment or a string.
  • The elevations that the fault trace will extend to.
  • The dip and dip directions; which can be selected from description fields, or typed if you would like to use a single value.
  • The graphics layer the surface will be sent to.
  • The numbers of the new strings.
  • The DTM object number.

Once that is completed, click “Apply”, and select the segment or string you want to triangulate into a fault plane. The result may look similar to below.

Each point of the string has been copied along the dip and dip direction until it reached the entered elevations. This was then triangulated automatically.

Note: If you would only like to extend the fault in one direction from the original trace, you can use the box selector to select the triangles along one side of the trace and delete them manually.

 

Looking for more Surpac Tips & Tricks? Read about How to Display Stratified Models in 3DVIA Composer and How to Handle CMS Data in Surpac.

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Kim Ferguson-Thomas

Kim Ferguson-Thomas

Technical Customer Support Consultant, GEOVIA at Dassault Systèmes
Kim Ferguson-Thomas has more than 20 years’ experience as a geologist in the mining industry, working in exploration, underground and open-cut mines within Australia.