Provided by: gmt-common_5.4.3+dfsg-1_all
gmtflexure - Compute flexural deformation of 2-D loads, forces, bending and moments
gmtflexure -Drm/rl[/ri]/rw -ETe[u]|D|file [ -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 associated arguments.
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 equations.
-Drm/rl[/ri]/rw 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. -ETe[u]|D|file 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.
-A[l|r]bc[/args] 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 optional arguments. -CpPoisson Change the current value of Poisson’s ratio [0.25]. -CyYoung Change the current value of Young’s modulus [7.0e10 N/m^2]. -Fforce] Set a constant horizontal in-plane force, in Pa m  -Qn|q|t[args] 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]. -S Compute the curvature along with the deflections and report them via the third output column [none]. -Twfile Supply a file with pre-existing deformations [undeformed surface]. -Wwd 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. -Zzm 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 on output. -e[~]”pattern” | -e[~]/regexp/[i] (more …) Only accept data records that match the given pattern. -h[i|o][n][+c][+d][+rremark][+rtitle] (more …) Skip or produce header record(s). -icols[+l][+sscale][+ooffset][,…] (more …) 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
2018, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe