Methods and apparatus are provided for generating velocity models for pre-stack depth migration (“PSDM”). Seismic, gravity and electromagnetic joint inversion input data are generated based on observed seismic, gravity and electromagnetic data (e.g., magnetotelluric and/or controlled source electromagnetic), and velocity, density and resistivity models. A joint inversion is performed to produce a multiparametric model that is a function of velocity, density and resistivity parameter distributions. The separate parameter distributions are extracted from the multiparametric model, and the extracted velocity model is used to perform a PSDM. A migration velocity analysis is performed on PSDM output to generate seismic image residuals. If the seismic image residuals meet predetermined quality objectives, the extracted velocity model is output as the final velocity model for PSDM. Otherwise, updated seismic, gravity and electromagnetic joint inversion input data are generated, and the process repeats in an iterative fashion until the seismic image residuals meet the predetermined quality objectives.