wave theory - kirchhoff migration

[Tingpingbing]

What type of wave theory is considered in Kirchhoff time migration?

[GuyM]

Seismic wave theory.

You are using an integral form of the wave equation.

SEG Wiki has you covered :
https://wiki.seg.org/wiki/Dictionary:Wave_equation
https://wiki.seg.org/wiki/Dictionary:Ki ... s_equation

[Tingpingbing]

Hey again,

what is also "sudden change in facies", "near-surface scattering" and "pinch out"?
What is a small scale feature?

Sorry that I ask so many questions.

[GuyM]

"Sudden change in facies" means that the rock type changes very quickly.

"near surface scattering" is where small faults and heterogeneities in the weathered layer diffract seismic energy; this is often under-sampled spatially and so appears as noise. It'sthe reason why you don't see further signal to noise improvement when you "vertically stack" multiple shots in the same location (ie when surveying with a hammer and plate) after a certain point. You are seeing complex near-surface backscatter (which stacks) not rando noise (which does not)

a "pinch out" is where you have a wedge-shape in the sub-surface, which might be a result of dipping rock layers being eroded and then having another material laid down on top, as an unconformity. You can also get pinchouts as a result of a depositional pattern, like a regressive shoreline.

"small scale feature" means some kind of anomaly or reflection that is not very big; a small fault, channel, reef, volcanic intrusion, or subtle structure.

[Tingpingbing]

Thank you so much