lateral velocity variations

[RaSaaLa]

what is stong lateral velocity variations and low lateral velocity variations?

[GuyM]

It's how fast the velocity varies horizontally.

If you had very boring geology - just horizontal, flat layers, deposited and compacted normally - then you would see a vertical variation in seismic velocity, but no lateral variations.

On the other hand, when you have those same flatish layers overlying salt (halite), eventually the buoyancy (low density) of the salt and the fact it is ductile (can flow) will lead the salt to bubble up into domes, much like the hot wax in a "lava lamp"

You'll then have a situation where you will go from the slow sedimentary layers into halite, which has a much higher seismic velocity (4500 m/s); so that would be a very rapid change in lateral velocity.

It's also an extreme example, you can get variations like this from faulting, depositional patterns, diagenetic changes and so on.