gmtflexure - Compute flexural deformation of 2-D loads, forces, bending and
-A[l|r][/args] ] [ -CpPoisson
] [ -CyYoung ] [ -Fforce ] [
-Qargs] [ -S ] [ -Twfile] [
-V[level] ] [ -Wwd] [ -Zzm] [
-bibinary ] [ -dnodata ] [ -eregexp ] [ -hheaders
] [ -iflags ] [ -oflags ]
Note: No space is allowed between the option flag and the
gmtflexure computes the flexural response to 2-D loads using a range of
user-selectable options, such as boundary conditions, pre-existing
deformations, variable rigidity and restoring force, and more. The solutions
are obtained using finite difference approximations to the differential
- Sets density for mantle, load, infill (optionally, otherwise it is assumed
to equal the load density), and water. If ri is not given then it
defaults to rl.
- Sets the elastic plate thickness (in meter); append k for km. If
the elastic thickness exceeds 1e10 it will be interpreted as a flexural
rigidity D instead (by default D is computed from Te,
Young's modulus, and Poisson's ratio; see -C to change these
values). Alternatively, supply a file with variable plate
thicknesses or rigidities. The file must be co-registered with any file
given via -Q.
- Sets the boundary conditions at the left and right boundary.
The bc can be one of four codes: 0 selects the infinity condition,
were both the deflection and its slope are set to zero. 1 selects the
periodic condition where both the first and third derivatives of the
deflection are set to zero. 2 selects the clamped condition where
args (if given) sets the deflection value  (and its first
derivative is set to zero), while 3 selects the free condition where
args is given as moment/force which specify the end
bending moment and vertical shear force [0/0]. Use SI units for any
- Change the current value of Poisson's ratio [0.25].
- Change the current value of Young's modulus [7.0e10 N/m^2].
- Set a constant horizontal in-plane force, in Pa m 
- Sets the vertical load specification. Choose among these three options:
-Qn means there is no input load file and that any deformation is
simply driven by the boundary conditions set via -A. If no rigidity
or elastic thickness file is given via -E then you must also append
min/max/inc to initiate the locations used for the
calculations. Append + to inc to indicate the number of
points instead. -Qq[loadfile] is a file (or stdin if not
given) with (x,load in Pa) for all equidistant data locations. Finally,
-Qt[topofile] is a file (or stdin if not given) with (x,load
in m or km, positive up); see -M for topography unit used [m].
- Compute the curvature along with the deflections and report them via the
third output column [none].
- Supply a file with pre-existing deformations [undeformed surface].
- Specify water depth in m; append k for km. Must be positive . Any
subaerial topography will be scaled via the densities set in -D to
compensate for the larger density contrast with air.
- Specify reference depth to flexed surface in m; append k for km. Must be
positive . We add this value to the flexed surface before output.
- -V[level] (more ...)
- Select verbosity level [c].
- -bi[ncols][t] (more ...)
- Select native binary input.
- -d[i|o]nodata (more ...)
- Replace input columns that equal nodata with NaN and do the reverse
- -e[~]"pattern" |
-e[~]/regexp/[i] (more ...)
- Only accept data records that match the given pattern.
- Skip or produce header record(s).
- Select input columns and transformations (0 is first column).
- -ocols[,...] (more ...)
- Select output columns (0 is first column).
- -^ or just -
- Print a short message about the syntax of the command, then exits (NOTE:
on Windows just use -).
- -+ or just +
- Print an extensive usage (help) message, including the explanation of any
module-specific option (but not the GMT common options), then exits.
- -? or no arguments
- Print a complete usage (help) message, including the explanation of all
options, then exits.
NOTE ON UNITS¶
The -M option controls the units used in all input and output files.
However, this option does not control values given on the command line
to the -E, -W, and -Z options. These are assumed to be in
meters unless an optional k for km is appended.
PLATE FLEXURE NOTES¶
We solve for plate flexure using a finite difference approach. This method can
accommodate situations such as variable rigidity, restoring force that depends
on the deflection being positive or negative, pre-existing deformation, and
different boundary conditions.
To compute elastic plate flexure from the topography load in topo.txt,
for a 10 km thick plate with typical densities, try
gmt flexure -Qttopo.txt -E10k -D2700/3300/1035 > flex.txt
gmt, gravfft, grdflexure, grdmath
2019, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe