migration of diffractions

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Tingpingbing
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migration of diffractions

Post by Tingpingbing »

Hello,
I do not understand it when the diffraction on the migration has two point. Why does the diffraction occur as two point?
It has a positive and negative point.
Where can I read more about this two point diffraction migration?

Thank you in advance for your help! :D

GuyM
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Re: migration of diffractions

Post by GuyM »

Can you post an image? And are you talking about 2D or 3D data?

Complex structures can create multiple diffractions; or rather by Huygen's principle every part of the interface is really acting to scatter the data, and you only see a reflection when those scattering points are sufficiently close in depth that the diffraction "tails" can combine.

So - every "reflection" is just a summed set of coherent diffractions.

On 2D data the structural complexity can be "out of plane" - that is to say energy reflecting in from the side of the survey. On marine data the airgun and receiver arrays are designed to help suppress this energy, but in structurally complex areas it's not enough. I've imaged both the up-thrown and down-thrown fault blocks in the past. Land data with explosive sources and node receivers is omni-directional - so you get more out-of-plane energy.

Hope this helps - but post a stacked section image if you want a more specific discussion...

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geophix
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Re: migration of diffractions

Post by geophix »

Tingpingbing wrote:
Tue May 19, 2020 5:40 pm
Hello,
I do not understand it when the diffraction on the migration has two point. Why does the diffraction occur as two point?
It has a positive and negative point.
Where can I read more about this two point diffraction migration?

Thank you in advance for your help! :D
You lost me too :(
A picture might be helpful to explain it better.

Tingpingbing
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Re: migration of diffractions

Post by Tingpingbing »

The diffraction looks like this. I do not have a better picture of it since it is an example.
The model is a simple structure with one diffraction. And this diffraction looks like this after migration.
This is a 2D migration.
Last edited by Tingpingbing on Wed May 20, 2020 8:40 am, edited 1 time in total.

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geophix
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Re: migration of diffractions

Post by geophix »

Oh, I see, you are referring the pinkish and blueish color regions as two points. I think they are just positive and negative responses of the same wavelet. As I understand, migration is mainly supposed to shrink the tails of a hyperbola ( collapses diffraction to improve horizontal resolutions), not the wavelet itself in the depth direction. For example, if the source wavelet has two sets of positive and negative responses, I think you will get 4 "points" after migration. This is based on my understanding of mainly GPR data processing. Seismic migration might be a little different, but should be very similar.

Tingpingbing
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Re: migration of diffractions

Post by Tingpingbing »

Thank you so much for your help :)
I understand now. I will check up the GPR data processing too.

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