Method for mapping a 3D grid or mesh from a faulted subsurface domain to a continuous design domain, wherein the grid may be used to represent a discrete model of a subsurface material property (such as permeability) to use, for example, in a reservoir simulator. The mapping is geometry-based, not physics-based. The mapping is determined by an iterative optimization procedure designed to penalize deformation of tessellated mesh cells (703) in the design domain compared to their geometric quality in the faulted domain (701), but subject to stitching constraints (702) appearing as a penalty term or Lagrange multiplier term in the optimization objective function to influence the final mesh to co-locate pairs of points identified on opposite sides of a fault as having been located together before the fault occurred.