1. A method for modeling seismic data using time preserving tomography, the method comprising: storing an initial set of parameter values representing an initial seismic data model, wherein the initial seismic model corresponds to at least a plurality of ray pairs each pair comprising a traveltime; and generating an altered model by altering two or more parameter values in the initial set of parameter values for each of the ray pairs in the initial model, wherein altering one parameter value without altering the remaining of the two or more parameter values corresponds to a change in the traveltime of each of the ray pairs and wherein altering the two or more parameter values in combination corresponds to no net change in the traveltime of each of the ray pairs.