1. A computer-implemented method for modeling deformation in subsurface strata caused by permafrost thaw, comprising: defining physical boundaries for a geomechanical system, the geomechanical system having an area that comprises a permafrost layer; acquiring mechanical properties of the permafrost layer and of at least one rock formation below the permafrost layer within the physical boundaries; acquiring initial thermal properties of the permafrost layer and of at least one rock formation below the permafrost layer within the physical boundaries; defining far-field boundary conditions affecting the geomechanical system; determining a thermal distribution within the permafrost layer and of the at least one rock formation below the permafrost layer within the physical boundaries in response to progressively warmer temperatures within the permafrost layer; determining specific gravity for the permafrost layer; inputting the mechanical properties, the initial thermal properties, the far-field boundary conditions, and the specific gravity into an initial geomechanical analysis module as part of a computer-implemented finite element analysis program; running the finite element analysis program based upon the initial geomechanical analysis module to determine in situ stress values within the geomechanical system at selected nodes at an initial time, thereby initializing a geostatic condition of the geomechanical system; providing a thermal analysis module based upon the thermal distribution; inputting the mechanical properties, the initial thermal properties, the far-field boundary conditions, and the thermal analysis module into an initialized geomechanical analysis module; running the finite element analysis program based upon the initialized geomechanical analysis module to determine displacement and strain values within the initialized geomechanical system at selected nodes at a subsequent time in response to an increase in temperature within the permafrost layer.