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Right-clicking on a Seismic Line or a Seismic Brick Cube and selecting "Seismic Trace Attributes..." pops up the following dialog:
Dip and Coherence dialog
The Coherence attribute is a byproduct of the dip telling us how reliable the InlDip and CrlDip estimates are: 0 <= Coherence <=1, where 1: absolute certain.
But it also a measure of "order" in the seismic. A non chaotic region of the seismic will have a high coherence, whereas a chaotic region, e.g. inside a salt, will have a low coherence.