# gmtflexure¶

gmtflexure - Compute flexural deformation of 2-D loads, forces, bending and moments

## Synopsis¶

**gmtflexure** **-D***rm*/*rl*[/*ri*]/*rw* **-E***Te*[**u**]|*D*|*file*
[ **-A**[**l**|**r**][/*args*] ]
[ **-C****p***Poisson* ] [ **-C****y***Young* ]
[ **-F***force* ]
[ **-Q***args*] [ **-S** ] [ **-T***wfile*]
[ **-V**[*level*] ]
[ **-W***wd*]
[ **-Z***zm*]
[ **-bi**binary ]
[ **-h**headers ]
[ **-i**flags ]
[ **-o**flags ]

**Note:** No space is allowed between the option flag and the associated arguments.

## Description¶

**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.

## Required Arguments¶

**-D***rm*/*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*.

**-E***Te*[**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**.

## Optional Arguments¶

**-A**[**l**|**r**]*bc*[/*args*]- Sets the boundary conditions at the
**l**eft and**r**ight 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 [0] (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.

**-Cp***Poisson*- Change the current value of Poisson’s ratio [0.25].
**-Cy***Young*- Change the current value of Young’s modulus [7.0e10 N/m^2].

**-F***force*]- Set a constant horizontal in-plane force, in Pa m [0]

**-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].

**-T***wfile*- Supply a file with pre-existing deformations [undeformed surface].

**-W***wd*- Specify water depth in m; append k for km. Must be positive [0].
Any subaerial topography will be scaled via the densities set in
**-D**to compensate for the larger density contrast with air.

**-Z***zm*- Specify reference depth to flexed surface in m; append k for km. Must be positive [0]. 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.

**-h**[**i**|**o**][*n*][**+c**][**+d**][**+r***remark*][**+r***title*] (more ...)- Skip or produce header record(s).

**-i***cols*[**l**][**s***scale*][**o***offset*][,*...*] (more ...)- Select input columns (0 is first column).

**-o***cols*[,...] (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.

## Examples¶

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