Erdi,

It looks like you have a zero phase wavelet in your signals.  The place to pick first arrivals is the black maximum.  Your arrow is on a side lobe.  Zero phase wavelets can be the result of correlation, like with a Vibroseis source.  Also, they can be a wavelet of choice in some programs that compute synthetic data.  If your data are synthetic, look into using a minimum phase wavelet, if it is available.

Paul

Dr. Paul Michaels, PE
Professor Emeritus, Engineering Geophysics
http://173.255.241.228
https://www.boisestate.edu/earth/people/paul-michaels/

Hello Everyone

I said before that I was trying to do Zero Offset VSP Processing. To do that, I tried to use free software is called MVSP and Crewes toolbox. My problem is that I can start picking first break arrivals from 4th trace, and I can not see and pick the first three traces when I look at the data during the picking.

The first software itself assigns negative values for the first three traces, which results in negative velocities. On the Crewes, I am trying to assign values like 0.001 0.002 0.003 before the 4th trace because the 4th trace's time is 0.006, which probably gives rise to wrong velocities.

In short, Can I do anything about this issue on Seismic Unix? Is there any chance to fix it?

I added one of my files and the screenshot zoomed where the problem is. I modeled and created this data on different code (fdelmodc). **The data is passive data, and I utilized the noises, recording 120s. So, when you look at my data, you need to zoom in to see closely.

Thank you

Best regards

Erdi

 

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