Quoted from: https://geodynamics.org/cig/software/relax/

The open-source program Relax evaluates the displacement and stress in a half space with gravity due to dislocations, Mogi sources, and surface tractions; and the nonlinear time-dependent deformation that follows due to power-law rheology materials in the bulk and/or rate-strengthening friction faults. The numerical method is based on a Fourier-domain elastic Green's function (Barbot & Fialko, 2010a; 2010b) and an equivalent body-force representation of co-seismic and post-seismic deformation processes (Barbot et al., 2009b). Application of the method for the 2004 Mw 6 Parkfield earthquake can be found in the work of Barbot et al. (2009b) and Bruhat et al. (2011). A coupled model of afterslip and laterally-heterogeneous viscoelastic flow following the 1999 Mw 7.6 Chi-Chi earthquake using relax is described by Rousset et al. (2012).

The possible applications for the earthquake-cycle modeling include: i) co-seismic displacement and Coulomb stress calculation, ii) quasi-static stress transfer between earthquakes due to a postseismic transient, iii) modeling of postseismic transients including nonlinear rheologies and multiple mechanisms, iv) cycle of multiple earthquakes and spin-up models, v) loading cycle of lakes or the monsoon. The distribution includes various examples for published coseismic slip distributions.

--Refer to https://geodynamics.org/cig/software/relax/