The open-source program RELAX uses a semi-analytic method described in Barbot & Filako (2010a, 2010b) to simulate time series of deformation in a three-dimension half space due to viscoelastic flow and fault creep. While other semi-analytic models of time-dependent three-dimensional viscoelastic deformation (Pollitz, 1997; Smith & Sandwell, 2004a; Johnson et al., 2009) are limited to linear constitutive laws and vertical variations in inelastic properties, the proposed technique is sufficiently general to handle laboratory-derived nonlinear rheologies and arbitrary variations in viscosity. The method uses the elasto-static Green function to solve for the instantaneous velocity in a Cartesian half space. A simpler alternative to finite-element softwares like PyLith, the method obviates the need of elaborate and time-consumming discretization of a computational domain and allows for complex fault geometries.

The Fortran 90 source code of RELAX, used to evaluate nonlinear time-dependent viscoelastic deformation and fault creep due to faulting and volcanic unrest can be downloaded here

• relax.tar [US mirror]

Some programs for post processing and visualization with gmt can be downloaded here

• util.tar [US mirror]

Some compilation options relate to the choice of FFT (CTFFT, FFTW, SGI DFT, Intel MKL DFT), output formats (text, xyz, VTK, GMT, Cartesian/geographic) and parallelization method (MPI or OpenMP). These options are explained in the readme file contained in the tar ball. See also some related comments about the elasto-static deformation code STATICU. Instructions and run examples can be found in the readme file.