## migration of diffractions

Anything about geophysics and geoscience: jobs, events, technical or general discussions ...
Tingpingbing
Silver Member
Posts: 34
Joined: Fri May 15, 2020 2:02 pm

### migration of diffractions

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.

GuyM
VIP Member
Posts: 644
Joined: Sat Mar 24, 2012 11:35 pm

### Re: migration of diffractions

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...

geophix
VIP Member
Posts: 933
Joined: Fri Jul 24, 2009 9:26 am

### Re: migration of diffractions

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.

You lost me too
A picture might be helpful to explain it better.

Tingpingbing
Silver Member
Posts: 34
Joined: Fri May 15, 2020 2:02 pm

### Re: migration of diffractions

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.

geophix
VIP Member
Posts: 933
Joined: Fri Jul 24, 2009 9:26 am

### Re: migration of diffractions

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
Silver Member
Posts: 34
Joined: Fri May 15, 2020 2:02 pm

### Re: migration of diffractions

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

nikkinemo95
Member
Posts: 1
Joined: Mon Aug 31, 2020 8:01 am

### Re: migration of diffractions

Diffractions are particularly useful for velocity analysis, because they carry immediate velocity information that does not depend on data redundancy. ... This residual- diffraction-moveout (RDM) method is based on adjusting ellipses or hyperbolas to the unfocused diffraction events after migration.

Tingpingbing
Silver Member
Posts: 34
Joined: Fri May 15, 2020 2:02 pm

### Re: migration of diffractions

Thanks for the explanation! What does data redundancy mean? Is that like reduce in the data or something?

• Similar Topics
Replies
Views
Last post