# Time Velocity Analysis

NMO Velocity Analysis
At Spectrum, velocities are picked interactively from gathers, stacks (constant or variable function) and semblance plots. Interpreted horizons can be overlaid on the velocity analyses to allow horizon consistent velocity picking.  Auto-picking of velocities is used whenever possible, using a robust workflow.  When properly constrained and effectively parameterized, auto-picking methods produce high quality consistent results and decrease project timelines significantly.

The velocities are checked interactively with NMO corrected gathers, velocity sections, seismic stacks, and iso-velocity plots. A regional Q.C. of all velocities is made and velocity and time maps can be produced.

For 3D datasets, a velocity cube is created and iso-velocity plots are produced for inlines, cross lines and constant time slices. Iso-velocity plots can also be produced for interpreted horizons and as 3-dimensional contour maps.

Fourth Order NMO
An optional fourth order NMO term is available which compensates for ray bending at far offsets. Following the initial velocity pick a contour plot of the C4 term is produced and also picked interactively.

Example Velocity Analysis Display
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