Step 30: Run NeoKinema (again) to interpolate stress directions

Use a plain-ASCII text editor (e.g., NotePad or EditPad Pro) to re-open your NeoKinema parameter file
(usually named p*.nki, where * is any additional project-identifying name you want to include).
In line #14, type the name of the stress-direction dataset file you created in the previous step, replacing “none”.

In line #15, choose integer value “1” or “2” to specify the stress-interpolation method.
The two options provided use similar algorithms, but had different calibration datasets, resulting in different styles.

· Method (1) [Bird & Li, 1996] uses non-parametric statistical relations inferred from a global dataset, the
World Stress Map, and emphasizes smooth stress fields across wide regions where data may be sparse.
It seems to give good performance across western North America, for example.

· Method (2) [Carafa & Barba, 2013, Geophys. J. Int., 193, 531-548] is optimized for performance in Europe
and other regions where data are abundant, and where length-scales may be smaller due to small microplates.
(In particular, it does a better job of matching the 90°-rotation of σ_1h that occurs at the NE front of the Apennines.)

Before you save the parameter file, consider what model-name token you might want to assign (in line #1)?
If you want to eventually compare predicted maps of principal strain-rate axes between this step and the previous step,
then you may want to keep the NeoKinema output files from the previous run, and not over-write them.
The simplest way to do this is to change the model-name token, which will be built into all output filenames.
For example, I often use “2019001” for the first model run in 2019, and 2019002 for the second, and so on.

Now save the parameter file, and also consider changing its name so that your new model-name token
becomes the * in the generic parameter file name p*.nki.  After all, parameter files are very small
(2 KB), and I find it helpful to keep a different version for each NeoKinema model I run.
They will be very helpful for plotting particular models with NeoKineMap, later.

Now run NeoKinema again, specifying the name of the newest parameter file (just created).
This time, you may notice a new time-consuming step, described as:
Interpolating stress directions (slow!!)…

When NeoKinema is finished, it will output the interpolated stresses in new file s*.nko
(note: .nkO = NeoKinema Output, whereas .nkI = NeoKinema Input as file-name extensions),
where * is the model-name token that you provided in line #1 of your latest parameter input file.
New file s*.nko includes stress directions interpolated to each element center, for plotting by NeoKineMap.
It is produced only if stress directions were input, and/or if faults were designated as stress indicators.
There are 4 columns in the file, in this order:

            element_number   successful_interpolation?   azimuth   standard_deviation

Element numbers refer to the .feg file used in the run of NeoKinema.
Successful_interpolation is a logical value (T/F).
Azimuth is in degrees clockwise from North.
Standard deviation (sigma) is also in degrees.
(If successful_interpolation = F, these last two values are meaningless, and should not be used in graphics.)