Seismic Unix Semblance-Constant Velocity Stacks

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Nightwolf
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Joined: Wed Dec 04, 2019 5:34 pm

Seismic Unix Semblance-Constant Velocity Stacks

Post by Nightwolf »

Hello all!

I am just wondering that my constant velocity stacks figure does not show high amplitude values for second and third reflectors (First one is ok).
Also, If I can see maximums for those to be picked in the semblance plot, that would be good. Are these related to parameters nvs and dvs values in my iva.sh script?

Finally, is there any chance of reducing the noises much more? For example, Does mute work on it?

I added the screenshots

Best
Attachments
velocity analysis.png
parameters.PNG

coreymorgan
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Re: Seismic Unix Semblance-Constant Velocity Stacks

Post by coreymorgan »

Firstly, that gather is way too noisy for velocity picking. Run a filter on it to get rid of some of that high f noise and maybe try a pass of radon or at least a gap decon to do something about those multiples since they are dominating your semblance in places. Also, your CVS panel only seems to show velocities from just below 1400 to 1600 m/s. Based on your parameters, it should show higher than that.

Nightwolf
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Re: Seismic Unix Semblance-Constant Velocity Stacks

Post by Nightwolf »

coreymorgan wrote:
Mon Feb 24, 2020 8:19 pm
Firstly, that gather is way too noisy for velocity picking. Run a filter on it to get rid of some of that high f noise and maybe try a pass of radon or at least a gap decon to do something about those multiples since they are dominating your semblance in places. Also, your CVS panel only seems to show velocities from just below 1400 to 1600 m/s. Based on your parameters, it should show higher than that.
Hi coreymorgan

I am actually using 2D finite difference wavefield modeling code by Jan Thorbecke to make model and for processing seismic unix. I am not using real data. I am using synthetic data. I can actually pick the first one (just under the 1s) and second one (just above the 2s). However, the things are changing after 2s. So, I am thinking that If I apply gain, which strengthens bottom reflections, it may be work?

Is it ok using filter on synthetic data? Does it affect my reflections negatively? There is also velan_radon script in the demos. is it useful for this?

I added my figures again. This time I zoomed my velocity figures and I added the file I am using (there are lot of CDPs after sorting data to cmp gathers)

Thanks
Attachments
velocity analysis.png
data used in velocity analysis(zoomed).png

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