Common Information

In addition to the finite-element mesh, PyLith requires files to specify the simulation parameters. We specify parameters common to all simulations in a directory in pylithapp.cfg, which contains numerous comments, so we only summarize the parameters here.

Metadata, Mesh, and Output

The pylithapp.metadata section specifies metadata common to all simulations in the directory. We set the parameters for importing the finite-element mesh in pylithapp.mesh_generator.

Physics

These quasi-static simulations solve the elasticity equation and include a fault, so we have a solution field with both displacement and Lagrange multiplier subfields.

(223)\[\begin{gather} \vec{s} = \left(\begin{array}{c} \vec{u} \quad \vec{\lambda} \end{array}\right)^T \\ \boldsymbol{\nabla} \cdot \boldsymbol{\sigma}(\vec{u}) = \vec{0} \end{gather}\]

We use the default TimeDependent problem and solution field with a single displacement subfield of basis order 1. In addition to output of the solution over the domain, we output the solution over the ground surface (+y boundary). For the domain we skip one time step between writing the solution to the file.

Listing 208 Solution and output parameters for all subduction-2d simulations.

[pylithapp.problem]
solution = pylith.problems.SolnDispLagrange

[pylithapp.problem]
solution_observers = [domain, groundsurf]
solution_observers.groundsurf = pylith.meshio.OutputSolnBoundary

[pylithapp.problem.solution_observers.domain]
# Skip 1 time step between output for the domain.
trigger.num_skip = 1

[pylithapp.problem.solution_observers.groundsurf]
# The `label` and `label_value` correspond to the name and tag of the
# physical group in the Gmsh Python script.
label = groundsurf
label_value = 10

The physical properties for each material are specified in spatial database files. For example, the elastic properties for the continental crust are in mat_concrust.spatialdb. The provided spatial database files all use just a single point to specify uniform physical properties within each material.

Listing 209 Material parameters for the subduction-2d example suite. We only show the details for the continental crust material.

[pylithapp.problem]
materials = [continent_crust, ocean_crust, mantle]

[pylithapp.problem.materials]
[pylithapp.problem.materials.continent_crust]
label_value = 1

db_auxiliary_field.description = Continental crust properties
db_auxiliary_field.iohandler.filename = mat_concrust.spatialdb

observers.observer.trigger.num_skip = 1

auxiliary_subfields.density.basis_order = 0
bulk_rheology.auxiliary_subfields.bulk_modulus.basis_order = 0
bulk_rheology.auxiliary_subfields.shear_modulus.basis_order = 0