Drag applied to fault traces page

This is the Next >> page accessed in WizGen (in "Flexible project" mode) from the Output - derived and user-defined properties page or by selecting the Goto... button for Apply stochastic and/or deterministic drag to faults from the Contents page when the Include fault drag and hierarchical zone effects option has been toggled "on" via the Title page of WizGen.

NOTE:- The next two pages can only be accessed in WizGen if the TransGen installation is licensed for the sub-resolution fault-trace functionality (new to the TransGen 3.2 release).

The Drag applied to fault traces page of WizGen allows the user to modify the fault throw on all fault traces in the model (either included explicitly in the geometry of the parent model or included as user-defined faults using the TGTHROW keyword) using any one of the following options:-

Do not apply Drag (default setting) where fault drag is omitted from the model, except where the drag is specified by a file containing TGDRAG keyword data, added to the current run via the Included Data page.

Use equation where fault drag is modelled using either or both equation options, i.e. Probablistic throw uncertainty and/or Deterministic normal drag.

Use a plugin where fault drag is modelled using the DRAG plugin written in the User-defined plugins page.

Do not apply drag options

If the default Do not apply Drag setting (as shown above) no throw modifications are applied to the current model, except where the drag ratio value included in the run via a file containing TGDRAG keyword data (see Included Data page) is anything other than 1.0.  

Use equation drag options

Select the Use equation option (as shown below) to access two basic options for modelling drag (Probablistic throw uncertainty and/or Deterministic normal drag).

Toggle "on" the Probablistic throw uncertainty and/or the Deterministic normal drag option(s) and input appropriate settings.
  
NOTE:- Both options can be used together to produce a model in which stochastic variability arising from uncertainty in the definition of the fault throws is modelled first and then deterministic geological normal drag is superimposed. This is the situation illustrated by the selections shown below.

Probabilistic throw uncertainty option

If the probabilistic throw uncertainty toggle is activated, fault drag is modelled stochastically using one of two options. These are an absolute uncertainty on fault throw (throw +/- m) or a percentage uncertainty on fault throw (throw +/- %). The fault throw value considered when calculating this uncertainty is the summation of the system throw (i.e. arising from the input model geometry) and the user-defined throw (added using the TGTHROW keyword via the Included Data page of WizGen).
As each trace is processed, a drag ratio is calculated which will result in the final fault throw either being in the range T = T± X metres, or T = T±Y %.

Examples of model parameters generated using the two methods are shown below. This functionality is designed to allow inclusion in the simulation model of stochastic variability arising from uncertainties in the definition of fault juxtapositions.

Throw +/- m

Drag ratios (a) and implied values of final output fault trace throw (b) are shown below plotted against input fault trace throws for a model containing input trace throws in the range of -60 to 60m using a throw +/- m setting of 10 metres.

Throw +/- %

Drag ratios (a) and implied values of final output fault trace throw (b) are shown below plotted against input fault trace throws for a model containing input trace throws in the range of -60 to 60m using a throw +/- % setting of 5%.

Deterministic normal drag option

This functionality is designed to allow inclusion in TransGen of the effects of normal drag developed during the evolution of the fault throw. The growth of displacement on a particular fault might consist initially of the development of a monocline with a discrete fault surface forming only after a particular displacement, followed by a progressively larger fraction of the accumulated displacement accommodated on the discrete slip surface.

The WizGen tool allows inclusion of such drag using the equation:

The figures below shows the form of this equation for two sets of values of the user-defined constants, i.e. for dt = 0.5m and dp = 20m (shown in black) and dt = 3m and dp =10m (shown in pink). All throw up to the value of dt is accommodated by normal drag and the component of throw accommodated by normal drag gradually decreases as throw increases, eventually plateauing out to the value of dp at very high throw.

For example the drag ratios (a) and the implied values of the final trace throw, i.e. output fault throw (b) for input trace throws in the range of -60 to 60m are shown for a model using dt = 0.5m and dp = 20m.

Overwrite user-defined drag ratios

This toggle (only accessible with the Use equation drag option selected) determines whether or not drag ratio values assigned using the TGDRAG keyword are preserved or overwritten by equation options defined on this page.

Use a plugin option

Toggle this option "on" to apply drag to fault traces using user-defined criteria applied via the DRAG plugin (see section on the DRAG plugin for full details).

When the Drag applied to fault traces page is set as required, click on the Next >> button to view/edit the current settings on the Hierarchical fault zone definition page.

Alternatively, click on the << Back button to return to the Output - derived and user-defined properties page.

Or click on the Contents button to access the Contents page to view/edit any of the current WizGen page settings, inspect the current TGDATA file and/or the session log generated by last ViewGen calculation.

Click on Save to save any modifications made to the current TGDATA runfile.
Click on Quit to exit from WizGen with or without saving the any changes to the TGDATA runfile.