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The problem addressed in seismic modeling, or simulation, is calculating the seismic response ([http://wiki.seg.org/wiki/Dictionary:Traveltime traveltime] and [http://wiki.seg.org/wiki/Dictionary:Amplitude amplitude]) for a given stratigraphic model. The stratigraphic model consists of those physical properties that influence seismic wave propagation—typically [http://wiki.seg.org/wiki/Dictionary:P-wave compressional wave] speed, [http://wiki.seg.org/wiki/Dictionary:S-wave shear wave} speed, and [http://physics.about.com/od/fluidmechanics/f/density.htm mass density]. This set of parameters can describe the simplest possible solid, called an [http://www.merriam-webster.com/dictionary/isotropic isotropic] [http://wiki.seg.org/wiki/Dictionary:Elastic_deformation elastic] solid. For some purposes, it is sufficient to consider the earth as an acoustic (fluid) medium characterized by only two parameters: sound speed (''υ'') and mass density (ρ). Seismic reflections are generated where there is a contrast in impedance (which is the product of velocity and density).

The problem addressed in seismic modeling, or simulation, is calculating the seismic response ([http://wiki.seg.org/wiki/Dictionary:Traveltime traveltime] and [http://wiki.seg.org/wiki/Dictionary:Amplitude amplitude]) for a given stratigraphic model. The stratigraphic model consists of those physical properties that influence seismic wave propagation—typically [http://wiki.seg.org/wiki/Dictionary:P-wave compressional wave] speed, [http://wiki.seg.org/wiki/Dictionary:S-wave shear wave] speed, and [http://physics.about.com/od/fluidmechanics/f/density.htm mass density]. This set of parameters can describe the simplest possible solid, called an [http://www.merriam-webster.com/dictionary/isotropic isotropic] [http://wiki.seg.org/wiki/Dictionary:Elastic_deformation elastic] solid. For some purposes, it is sufficient to consider the earth as an acoustic (fluid) medium characterized by only two parameters: sound speed (''υ'') and mass density (ρ). [http://wiki.seg.org/wiki/Dictionary:Reflection Seismic reflections] are generated where there is a contrast in impedance (which is the product of velocity and density).

==Velocity data sources==

==Velocity data sources==