Step 14: Consider minimum (and maximum?) limits on fault offset rates?

Every fault included in a NeoKinema model requires a geologic offset-rate target (which may be zero) and associated uncertainty (which may be huge!).
In Step 11, we already computed some better target offset-rates and uncertainties with program Slippery, and arranged them into a table.

NeoKinema also offers the OPTION to add firm lower-limits and upper-limits on each offset-rate.
This option greatly increases the realism of the resulting models; for example, it can prevent faults from slipping in the wrong direction!
Therefore, this opportunity should be seized in most cases.

Lower-limits and upper-limits on offset-rates (if used) go into Column I and Column J (respectively) of the fault-offset-rate data table that we began to create in Step 11.
Their units are mm/a ( = km / Ma), just like the values in Columns D (target offset rate) and E (associated standard deviation, or “sigma”).
These values (if used) would usually be non-negative.

There are 3 ways that you can choose to treat each fault:

1. Accept the 95%-confidence bounds on geologic offset rate that were already computed by program Slippery (and which are already entered in the table).
Admittedly, this means treating 95%-confidence limits as if they were 100%-confidence limits, which is a slightly artificial reduction of uncertainty.
On the other hand, these values are algorithmic, objective, and reproduceable, with no subjective component.

2. Set the lower-limit to “0.0” (in Column I), but leave the upper limit blank (in Column J).
This will prevent the fault from slipping the “wrong way” (e.g., Thrust instead of Normal, or Right-lateral instead of Left-lateral).
If you are not convinced about the validity of the specific limits coming from Slippery, this may be a reasonable option.

3. Leave both columns empty, so that there are no firm limits on offset rate (just the “soft” limits implied by the Gaussian distribution described in Columns D and E).
This option should probably be reserved for those few faults whose slip-sense is really unknown.