[Seisunix] VSP Processing

John Chamberlain jxchamberlain at candg.me.uk
Thu Aug 6 10:22:02 CEST 2020


Erdi - from your image it looks like you are generating the synthetic 
data using a zero-phase wavelet but are then picking using a first-break 
approach (assuming that the arrow represents the pick on the 4th trace). 
I would suggest either picking on a peak using a threshold or modelling 
using a minimum phase wavelet. As Rob says, you could shift the data 
down with sushift but I suspect that the modelling has not created any 
data before T=0 so this might not work.

Another alternative would be to set a negative start time in the 
modelling if this is an option.

Regards
John Chamberlain

On 06/08/20 06:59, rob at xsgeo.com wrote:
>
> I would use sushift to delay the traces and then subtract the delay 
> from the subsequent picks generated by sufbpickw
>
> Regards
>
> Rob
>
> *From:*Seisunix <seisunix-bounces at mailman.seismic-unix.org> *On Behalf 
> Of *Erdi Apatay
> *Sent:* Wednesday, 5 August, 2020 11:30 PM
> *To:* seisunix at mailman.seismic-unix.org
> *Subject:* [Seisunix] VSP Processing
>
> Hello All
>
> I am trying to pick first break arrivals in Zero Offset VSP on the 
> Crewes toolbox and another software. My problem is that I start 
> picking from 4th trace because I cannot see the first three traces 
> when I look at my data, which results in wrong velocities.
>
> My data is passive zero-offset VSP data, utilizing ambient noise 
> sources. I created this by using a modeling code.
>
> I added one of my data and the problem's screenshot
>
> Can I fix this on Seismic Unix?
>
>
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