Step 7: Edit labels in the fault-traces file; add dips?

At this point, you should have a .dig file with fault traces in (longitude, latitude) coordinates.  (If you have any questions about .dig format, they should be answered here.)

Open this file in a plain-ASCII text editor (such as NotePad, or EditPad Pro) and edit the headers for each digitized trace:

Ø If you did not already type-in the names of fault traces (while digitizing), then do this now.
Use the handwritten notepad list that you created earlier (while drawing the fault traces in colored pencil) as a reference.
For example,
F0001R
might become
F0001R  San Andreas (Big Bend section) dextral fault, CA
and
F0015N
might become
F0015N  normal fault, 107W, 37-36N, CA
(Notice that there should usually be two spaces after any FnnnnV-type tag, but just one space after any FnnnnVW-type tag.  The reason will appear later, in Step 10.)

TRY to keep your fault-trace-names down to 50 characters maximum (including spaces), to avoid truncation in later steps of this NeoKinema modeling process.
This may require you to use abbreviations.  However, do NOT abbreviate critical fault names such as “Hayward-Calaveras” because that could cause a later text-based Search or Find operation to fail.
Instead, abbreviate the “generic” words in a fault-trace name, such as: “dex.” for “dextral”, “det.” for “detachment”, “sin.” for “sinistral”, “sub.” for “subduction”, “se.” for “section” or “segment”, “n.” for “normal”, “th.” for “thrust”, “tr.” for “train”, and of course “f.” for “fault”.
I also like to use official post-office abbreviations for the names of states and provinces in North America, such as: “WY” for “Wyoming”, “BC” for “British Columbia”, and “B.C.” for “Baja California”.  (You can see that the latter two could easily be confused if one were not careful.)  If your study area includes several countries, it might be good to use the international system of 2-letter country codes (e.g., IT = Italy/Italia; GR = Greece/Hellenic Republic).  If the fault trace crosses political boundaries, this can be indicated by multiple political abbreviations joined with hypens (e.g., “F0166N East Cache fault zone, UT-ID”).  The abbreviation “off” (short for “offshore”) is also useful.

Ø Or, perhaps you entered fault names while digitizing with program Didger5 (from Golden Software),
but you had to divide any long fault names into several data fields. 
In that case, remove any extra line-breaks now.  For example,
F0001R
San Andreas (Big Bend section)
dextral fault, CA
should now be corrected to read:
F0001R  San Andreas (Big Bend section) dextral fault, CA

Ø Another important edit at this time is to add dip angles for any faults where these are known.
Insert an extra header line (after the fault # & name) beginning with the characters “dip_degrees “ and then insert the dip angle.  For example,
F4279LT Santa Susana alt 1 fault, CA
dip_degrees  55
 -1.18767E+02,+3.43594E+01
 -1.18708E+02,+3.43506E+01
 -1.18634E+02,+3.43330E+01
 -1.18616E+02,+3.43229E+01
 -1.18581E+02,+3.43204E+01
 -1.18546E+02,+3.43003E+01
 -1.18523E+02,+3.43053E+01
 -1.18496E+02,+3.43242E+01
*** end of polyline ***

You should know that program NeoKinema contains default dips which will apply to any fault trace that does not have a “dip_degrees” data tag.  These default dips are: 20° for thrust/reverse faults; 55° for normal faults, 90° for strike-slip faults, and 14° for subduction zone megathrusts.  Actually, 55° is probably a very BAD estimate of the dip of most detachment faults (with dominant-offset-type “D”), so try to supply more realistic dip estimates for each of them.  Although the dip of a detachment may be locally zero (within a metamorphic core complex), “0” is not a legal fault dip in NeoKinema, so estimate the (steeper) dip where the fault dives underground and has its seismogenic portion in the upper crust.

These fault dips (either actual, or generic) will be used at 3 points in the NeoKinema modeling process:

Ø Whenever the dip-slip component of any geologic slip-rate is constrained by a throw-rate datum (type “T” or “N”, giving relative vertical velocity across the fault), NeoKinema will use the fault dip to convert this constraint to a heave-rate constraint (type “P” or “D”, giving relative horizontal velocity component in the direction perpendicular to the fault trace).

Ø If interseismic velocities at GPS benchmarks are provided to NeoKinema, it will convert them from interseismic velocities to long-term-average velocities by adding the current model estimate of the “mean coseismic velocity” (due to all model seismic moment rate, on all modeled faults).  It does this by summing solutions for many rectangular and triangular dislocation patches in an elastic half-space.  The dip angles of these dislocation patches are taken from the fault dips.

Ø If output from a successful NeoKinema model is passed to program Long_Term_Seismicity [as described near the end of this tutorial], Long_Term_Seismicity will forecast a greater earthquake rate along faults of gentle dip (due to their greater seismogenic widths, above the brittle/ductile transition depth), and will also spread this forecast seismicity further from the surface trace of the fault.

Therefore, it is very desirable for all fault dips to be correct (or, at least, plausible).