1. A method of developing a velocity model for processing a seismic dataset, comprising: at a computer system having a processor and memory: interpreting initial geological structures from the seismic dataset; building an initial basin model from the initial geological structures and rock properties derived from at least one of laboratory measurements, petrophysical properties, and mechanical earth models; validating the initial basin model using calibration data; determining pore pressure and effective stress from the validated initial basin model based on horizontal permeability and vertical permeability; transforming the effective stress into a basin model-based velocity model with one or more transform functions based on petrophysics; generating a seismic tomographic velocity model from the seismic data using seismic tomography; building a hybrid velocity model including a plurality of regions by selecting velocities from the basin model-based velocity model or from the seismic tomographic velocity model in each region; and using the hybrid velocity model for processing the seismic dataset to produce a high-quality seismic image to reduce oil and gas exploration risk and minimize drilling dry holes.