A computer-implemented method for determining a velocity model, comprising: receiving a first velocity model having a first symmetry approximation of a media of a subterranean domain, wherein the first symmetry approximation is a transversely isotropic approximation and the first velocity model is a tilted transversely isotropic model; receiving seismic data representing a subterranean formation; determining, by operation of a processor, a second velocity model having a second symmetry approximation of the media, the second symmetry approximation being less symmetric than the first symmetry approximation, wherein the second symmetry approximation is an orthorhombic anisotropic approximation and the second velocity model is a tilted orthorhombic model, wherein the second velocity model is determined based on an estimate of residual moveout of the first velocity model as a function of azimuth and one or more differentials that relate one or more changes in residual moveout as a function of azimuth to one or more orthorhombic parameters of the second velocity model; migrating the seismic data using the second velocity model; determining whether to update the second velocity model after migrating the seismic data to the second model and if the second velocity model needs to be updated: applying an update to the first velocity model to generate an updated second velocity model, wherein determining the second velocity model comprises: picking reflection events to measure residual moveout after migration using the first velocity model; calculating a tomographic update based on the one or more differentials; and applying the tomographic update to the first velocity model to generate the second velocity model. receiving a first velocity model having a first symmetry approximation of a media of a subterranean domain, wherein the first symmetry approximation is a transversely isotropic approximation and the first velocity model is a tilted transversely isotropic model; receiving seismic data representing a subterranean formation; determining, by operation of a processor, a second velocity model having a second symmetry approximation of the media, the second symmetry approximation being less symmetric than the first symmetry approximation, wherein the second symmetry approximation is an orthorhombic anisotropic approximation and the second velocity model is a tilted orthorhombic model, wherein the second velocity model is determined based on an estimate of residual moveout of the first velocity model as a function of azimuth and one or more differentials that relate one or more changes in residual moveout as a function of azimuth to one or more orthorhombic parameters of the second velocity model; migrating the seismic data using the second velocity model; determining whether to update the second velocity model after migrating the seismic data to the second model and if the second velocity model needs to be updated: applying an update to the first velocity model to generate an updated second velocity model, wherein determining the second velocity model comprises: picking reflection events to measure residual moveout after migration using the first velocity model; calculating a tomographic update based on the one or more differentials; and applying the tomographic update to the first velocity model to generate the second velocity model. applying an update to the first velocity model to generate an updated second velocity model, wherein determining the second velocity model comprises: picking reflection events to measure residual moveout after migration using the first velocity model; calculating a tomographic update based on the one or more differentials; and applying the tomographic update to the first velocity model to generate the second velocity model. picking reflection events to measure residual moveout after migration using the first velocity model; calculating a tomographic update based on the one or more differentials; and applying the tomographic update to the first velocity model to generate the second velocity model.