1. A method for perturbing an initial three-dimensional (3D) geological model including a fault using a 3D vector field, the method being executed by a processor according to software instructions, the method comprising: using the processor, generating a coherent 3D vector field comprising 3D vectors, wherein each 3D vector of the 3D vector field is associated with a node of the initial 3D geological model and has a magnitude within a range of uncertainty of the node of the initial 3D geological model associated therewith, wherein a plurality of the 3D vectors of the 3D vector field have different directions in a 3D space; and using the processor, applying the coherent 3D vector field to the initial 3D geological model including the fault to generate a perturbed 3D model, wherein the fault is a non-vertical fault, wherein the perturbed 3D model differs from the initial 3D geological model by a displacement in the different directions in the 3D space defined by the 3D vector field associated with nodes having uncertain values; and displaying the perturbed 3D model.