Configuration Files

gFlex can be driven by a YAML configuration file rather than (or alongside) the programmatic Python API. Pass the file path to the gflex CLI or to an F1D / F2D constructor. The file must have a .yaml or .yml extension.

Parameters

mode section

dimension

1 or 2. Selects a 1-D (profile) or 2-D (map-view) flexural solution.

method

Solution method:

  • fd — Finite Difference. Supports spatially variable elastic thickness. Requires a grid (dx, and dy in 2-D).

  • fft — Spectral (Fast Fourier Transform). Requires scalar (uniform) \(T_e\). Spectrally accurate and fast. When all boundary conditions are periodic the domain tiles exactly; for any other boundary condition the load is zero-padded by \(4\alpha\) on each side, approximating the no_outside_loads condition. In-plane stresses (\(\sigma_{xx}\), \(\sigma_{yy}\), \(\sigma_{xy}\)) are supported.

  • sas — Superposition of Analytical Solutions. Constant elastic thickness only; fast and analytically exact.

  • sas_ng — SAS on an unstructured point set (NG = “no grid”). Load and output locations are arbitrary (x, q0) or (x, y, q0) columns; see loads below.

parameter section

youngs_modulus

Young’s modulus \(E\) [Pa]. Typical lithospheric value: 65 GPa (6.5e10).

poissons_ratio

Poisson’s ratio \(\nu\) [dimensionless]. Typical value: 0.25.

gravitational_acceleration

Gravitational acceleration \(g\) [m s⁻²]. Earth standard: 9.8.

mantle_density

Density of the mantle \(\rho_m\) [kg m⁻³]. Typical value: 3300.

infill_material_density

Density of the material that fills (or vacates) the flexural depression \(\rho_\text{fill}\) [kg m⁻³]. Common values:

  • 0 — air (no infill)

  • 1030 — seawater

  • 2000–2700 — sediment

If the infill density varies spatially (e.g., at a subsiding shoreline that progressively floods), iterate externally: flex, update the inundation mask, re-flex, repeat.

input section

loads

Path to the load file.

  • Gridded methods (FD, SAS): a space-delimited array of surface normal stresses [Pa] (\(\rho g h\)). Grid cell area (\(\Delta x \times \Delta y\)) is applied internally to convert stress to force.

  • SAS_NG: a space-delimited file with columns (x, q0) in 1-D or (x, y, q0) in 2-D, where q0 is a point force [N].

Paths are resolved relative to the directory containing the configuration file.

elastic_thickness

Elastic thickness [m]. Either a scalar value or a path to a space-delimited array. Arrays are required for FD solutions with spatially variable Te. Use smooth_pad_Te() and pad_domain() (2-D) or smooth_pad_Te_1d() and pad_domain_1d() (1-D) to extend a variable-Te grid with a smooth boundary buffer before running.

xw, yw

(SAS_NG only) Vectors of x (and y for 2-D) coordinates at which to evaluate deflection. If omitted, deflection is evaluated at the load points.

output section

deflection_out

Path for writing deflection output as a space-delimited ASCII file. Leave blank to suppress file output.

plot

Controls inline plotting after the run:

  • q — plot the applied load.

  • w — plot the deflection.

  • both — deflection and load in separate subplots.

  • combo — (1-D only) deflection with the load overlaid.

Any other value (or blank) suppresses plotting.

numerical section

grid_spacing_x

Grid cell size in the x-direction [m].

boundary_condition_west, boundary_condition_east

Boundary conditions on the west and east edges.

For FD: zero_displacement_zero_slope (alias clamped), zero_displacement_zero_moment, zero_moment_zero_shear (alias free), zero_slope_zero_shear (alias mirror), or periodic. See Boundary Conditions for the physical meaning of each and guidance on choosing.

For SAS / SAS_NG: no_outside_loads (assumed if left blank).

Note

In-plane stresses (\(\sigma_{xx}\), \(\sigma_{yy}\), \(\sigma_{xy}\) [Pa]) cannot be set from a configuration file. They must be assigned programmatically before calling initialize():

flex.sigma_xx = 1e6   # east–west compression [Pa]
flex.sigma_yy = 0.
flex.sigma_xy = 0.

All three default to zero if not set. They are supported by fd and fft in 2-D, and by fd and fft in 1-D (sigma_xx only). Setting them with sas or sas_ng raises a warning and has no effect. See Theory for the governing equations.

numerical2D section

grid_spacing_y

Grid cell size in the y-direction [m].

boundary_condition_north, boundary_condition_south

Same options as boundary_condition_west / boundary_condition_east.

latlon

true / false. Interpret input coordinates as geographic latitude and longitude. Default: false.

planetary_radius

Planetary radius [m]. Required when latlon = true. Earth: 6 371 000 m.

verbosity section

verbose

true / false. Print progress messages during the run. Default: true.

debug

true / false. Print internal arrays and solver diagnostics. Default: false.

quiet

true / false. Suppress all output. Overrides verbose and debug. Default: false.

Complete examples

1-D finite-difference example (YAML)

# All units are SI.

mode:
  dimension: 1
  method: fd

parameter:
  youngs_modulus: 6.5e10
  poissons_ratio: 0.25
  gravitational_acceleration: 9.8
  mantle_density: 3300
  infill_material_density: 0

input:
  loads: q0_sample/1D/central_block.txt
  elastic_thickness: Te_sample/1D/8km_20km_ramp.txt

output:
  deflection_out: ""
  plot: combo          # overlay deflection and load (1-D only)

numerical:
  grid_spacing_x: 6000
  boundary_condition_west: periodic
  boundary_condition_east: periodic

verbosity:
  verbose: false
  debug: false
  quiet: false

2-D finite-difference example (YAML)

# All units are SI.

mode:
  dimension: 2
  method: fd

parameter:
  youngs_modulus: 6.5e10
  poissons_ratio: 0.25
  gravitational_acceleration: 9.8
  mantle_density: 3300
  infill_material_density: 0

input:
  loads: q0_sample/2D/diag.txt
  elastic_thickness: Te_sample/2D/fault_24-30.txt

output:
  deflection_out: ""
  plot: both

numerical:
  grid_spacing_x: 4000
  boundary_condition_west: zero_moment_zero_shear
  boundary_condition_east: zero_displacement_zero_slope

numerical2D:
  grid_spacing_y: 4000
  boundary_condition_north: mirror
  boundary_condition_south: zero_slope_zero_shear

verbosity:
  verbose: false
  debug: false
  quiet: false