## stacking trajectory

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RaSaaLa
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### stacking trajectory

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Last edited by RaSaaLa on Sun Aug 30, 2020 4:30 pm, edited 1 time in total.

RaSaaLa
Silver Member
Posts: 14
Joined: Tue Aug 18, 2020 8:02 am

### Re: stacking trajectory

Hello again,
What do also relative midpoint mean?

GuyM
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### Re: stacking trajectory

These are not commonly used terms; perhaps if you provide the wider context (that is to say the paragraph or paper they are in) I might be able to shed some light?

RaSaaLa
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Posts: 14
Joined: Tue Aug 18, 2020 8:02 am

### Re: stacking trajectory

"This idea of the CRS stack method is to use a second order approximation of the squared traveltime in the vincinity of the normal ray as a stacking trajectory" - from Common-reflection-surface-based workflow for diffraction imaging - (Dell and Gajeski, 2011)

"The former also enters into the NMO velocity vNMO, but cannot be separated from the medium velocity using only CMP gathers. However, by introducing a new data dimension, the off-CMP or relative midpoint coordinate, both new parameters become independent. Therefore, the general
traveltime function in the midpoint-offset domain depends on three independent parameters and
represents a whole surface in a block of adjacent CMP gathers instead of a one-parametric curve
within a single CMP gather." - from CRS Stacking – A Simplified Explanation - (Mann et al. 2007)

GuyM
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### Re: stacking trajectory

Ah - right so this is in the context of CRS. Understood.

Broadly that's saying you are not just taking data from a single common mid-point bin as you would with a conventional stack, but introducing more traces from the surrounding area; that's because the "normal ray" CMP stack only works perfectly when you have flat horizontal layers and no vertical or lateral variation in velocity.

One of the advantages of CRS is better noise suppression, simply because you are stacking more traces than you would with conventional stacking. It can also be useful when velocities vary rapidly laterally and vertically, which is more common in hard-rock settings.

RaSaaLa
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Posts: 14
Joined: Tue Aug 18, 2020 8:02 am

### Re: stacking trajectory

Thank you so much for your help, Sir.

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