-
Labeled gravity data file with inversion parameters. Format (created
by editing the output of the gravmerge program above) is:
(Ns Nit drho) (Ns = No. of measurements; Nit = Max no. of iterations;
107 100 -0.6 drho = density contrast, g/cc, negative here to match basin)
(Xproj mGal Sta) (Xproj = distance along line of projection, m)
-100.0 39.7 200
0.0 40.3 201
112.9 35.5 202
. . .
-
C source code for a pre-processor for above gravity data files.
Compile with:
cc -o gravin gravin.c
-
Preprocessed gravity data file with inversion parameters, ready for
inversion program. Format is:
(Ns Nit drho)
107 100 -0.6
(X1 X2 mGal) (X1 = distance of left side of column, km; X2 = distance
-0.05 0.05 -1.6 of right side of column, km; MGal normalized so maximum
0.05 0.15645 -1 in survey is zero, to match negative drho)
0.15645 0.29415 -5.8
. . .
-
C source code for Louie's translation of C. Langston's version of Talwani's inversion.
Compile with:
cc -o grav2d grav2d.c -lm -lget
-
UNIX shell script that runs preprocessing and inversion. Contains the
commands below, with projection distances given in meters and an inversion
fit tolerance of 5 mGal:
gravin meters < grav.in > grav.gravin
grav2d tol=5 < grav.gravin > grav.out
-
Output file of the grav2d program. The depths below are total lengths
of vertical prisms having the stated density contrast.
All distances and depths are in kilometers. Note that wild gravity data
values will generate wild depths. Format:
107 Elements, 100 Iterations Max, 5 Tolerance, drho=-0.6
(54 iteration outputs prior to convergence deleted)
Iteration 55:
Elem X1 X2 Depth Gcalc Gmeas
0 -0.05 0.05 0.1327 -1.6 -1.6
1 0.05 0.1565 0.02694 -1 -1
2 0.1565 0.2942 2.609 -5.257 -5.8
. . .
-
PostScript plot of grav2d output made with the Mac program
Graf.
-
C source code for a program to average neighboring gravity values
spatially and avoid the wild inversion of sharp changes in measured
gravity. Compile with:
cc -o gravavg gravavg.c
Then run, for example, with the command:
gravavg width=3 < grav.in > smgrav.in
which will do a central average of three neighboring points.
-
gravavg output ready for gravin preformatting, before the grav2d inversion.
- Gordon Shields's 1994
Fall AGU poster on southern Pahrump Valley results showing
smoothed gravity data and corresponding
basin-depth model estimated with Talwani's method.
