[Seisunix] Processing from Scratch

[walid Osman]

hello there http://www.freeusp.org/RaceCarWebsite/TechTransfer/Tutorials/Processing_2D/Data/2D_Land_data_2ms.tgz this is a link for Seismic 2 D line which we can share knowledge and efforts to start working on it and it will be a good tutorial for all of us. so would you help each other amd start this project step by step. Best Regards Walid Rudwan Osman

[Heigl, Werner]

Walid, this is good. Thanks for pointing out this link.

 

For a while I have been searching for an uncorrelated vibroseis data set. Would you know of any?

 

Thanks,

Werner

 

---

[John Stockwell]

Dear Walid,

That is a great idea. For starters the instructions are:
1) download the file from
http://www.freeusp.org/RaceCarWebsite/TechTransfer/Tutorials/Processing_2D/Data/2D_Land_data_2ms.tgz

2) move the file to a convenient location and extract its contents via
zcat 2D_Land_data_2ms.tgz | tar -xvf -

3) cd into the resulting directory. The file Line_001.sgy may be
converted to SU format via:

segyread tape=Line_001.sgy verbose=1 | segyclean > Line_001.su

4) I do the following

surange < Line_001.su

and copy and past the output from surange into a file called Notes.

5) geometry setting --- ok here is a point for someone else to figure
out how to get that info into the headers.

John Stockwell | jo...@dix.Mines.EDU
Center for Wave Phenomena (The Home of Seismic Un*x)
Colorado School of Mines
Golden, CO 80401 | http://www.cwp.mines.edu/cwpcodes
voice: (303) 273-3049

Our book:
Norman Bleistein, Jack K. Cohen, John W. Stockwell Jr., [2001],
Mathematics of multidimensional seismic imaging, migration, and inversion,
(Interdisciplinary Applied Mathematics, V. 13.), Springer-Verlag, New York.

[walid Osman]

I think the Second step is to separate the Auxillary channel from the Seismic Data channel which mean we have to look to the Trace ID header and do that. Walid Rudwan Osman     --- On Wed, 3/25/09, John Stockwell <jo...@dix.mines.edu> wrote:

[ionelia panea]

Hi, We can do it:   suwind < file.su key=tracf min=1 max=282 > file1.su   Regarding the geometry, I think we have to calculte it for a "crooked line", I know how to do it in Promax but I don't know in SU.   Regards, Lili.   --- On Thu, 3/26/09, walid Osman <w_r_...@yahoo.com> wrote:

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[Dominique Rousset]

Le Thursday 26 March 2009 09:25:33 ionelia panea, vous avez écrit :
> Regarding the geometry, I think we have to calculte it for a "crooked
> line", I know how to do it in Promax but I don't know in SU.
> Regards, Lili.

Hi,
Please find attached a small piece of code we wrote last year with a student
in order to perform cdp binning along crooked lines.
- the bins are located along straight segments. If the cdp line is really
complex (dont process in 2D !), use small straight segments.
- the line must be monotonously increasing in the X dimension. If if it's not,
rotate the coordinates before processing. If there is no rotation which
transform the coordinates as required (is it 2D reflection seismics ?), cut
your line into pieces.
- the trace wil bear the number of the nearest bin if it's close enough from
the actual midpoint.

I planned the following enhancements :
- included rotation of the coordinates in order to automatically match the
increasing X condition.
- output the traces as many times as there is a CDP bin close enough from the
actual mid point. This would allow to increase the stack fold.

Please try it
D.

--
|Dominique Rousset Modélisation et imagerie en géosciences - UMR 5212|
|Univ. Pau et des Pays de l'Adour BP 1155 F-64013 Pau Cedex - France|
|mailto:dominiqu...@univ-pau.fr http://migp.univ-pau.fr|
|Fixe:+33 5 59 40 74 23 | Mobile: +33 6 60 86 13 91 | Fax: +33 5 59 40 74 15|

[walid Osman]

Does any one applied The Geometry for this Data? Walid Rudwan Osman     --- On Thu, 3/26/09, Dominique Rousset <dominiqu...@univ-pau.fr> wrote:

From: Dominique Rousset <dominiqu...@univ-pau.fr> Subject: Re: [Seisunix] Processing from Scratch

_______________________________________________

[Glenn Reynolds]

I loaded the geometry with:

0. suwind<shots.su key=trid min=1>data.su

- strips the auxiliaries

1. gawk -f geom.awk Line_001.XPS >myheaders.txt

- makes all the headers. It is a script that loads the SPS,RPS and XPS files and writes sx,sy,selev,sstat,gx,gy,gelev,gstat,offset in that order, as tab-separated text. It's at the bottom of this note.

2a. wc <myheaders.txt

2b. surange <data.su

- confirms we have the right number of headers - both commands return 70782

3a. a2b <myheaders.txt n1=9 > myheaders.bin

- makes the geometry binary - note that the filesize is 4*9*70782=2548152, which is correct (9 headers in my implementation at 4 bytes per float for binary storage)

3b. sushw<data.su infile=myheaders.bin key=sx,sy,selev,sstat,gx,gy,gelev,gstat,offset >data_with_geom.su

- merges geometry into the trace headers. use "key=key1,key2,..." as the infile=binary method in sushw's help doesn't work

- glenn

GEOM.AWK

----------------------------------------------

BEGIN{

FIELDWIDTHS="1 16 8 1 2 4 4 4 2 4 9 10 6 3 6"

while(getline<"Line_001.SPS"){

if($1=="S"){

ep=$3

sx[ep]=$11

sy[ep]=$12

selev[ep]=$13

stats[ep]=$6

#print ep,sx[ep],sy[ep],selev[ep],stats[ep]

}

}

while(getline<"Line_001.RPS"){

if($1=="R"){

rp=$3+0.0

gx[rp]=$11

gy[rp]=$12

gelev[rp]=$13

gstat[rp]=$6

#print rp,gx[rp],gy[rp],gelev[rp],gstat[rp]

}

}

FIELDWIDTHS="1 6 4 1 1 16 8 1 4 4 1 16 8 8 1"

OFMT="%.8g"

OFS="\t"

}

/X/{

fldr=$3;ep=$7;

ch1=$9;ch2=$10;

r1=$13+0.0;r2=$14

for(i=r1;i<=r2;i++){

ox=gx[i]-sx[ep];oy=gy[i]-sy[ep]

cdpx=(sx[ep]+gx[i])/2

cdpy=(sy[ep]+gy[i])/2

print  sx[ep],sy[ep],selev[ep],stats[ep],gx[i],gy[i],gelev[i],gstat[i],sqrt(ox^2+oy^2)

}

}

----------------------------------------------

[Saied Hossein Hashemi]

Dear All,

It is a good idea to go for the processing of this line stage by stage, but it seems the latest communication is just stopped in the phase of applying the geometry. Does anybody managed to finish this phase for this line practically?

Regards,

Hosein

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[Saied Hossein Hashemi]

[Glenn Reynolds]

Has anyone tried to load the geometry using their own scripts or the scripts I supplied earlier? Source and receiver locations and statics are loaded to trace headers. We must also change the "scalco" header to 1 on all traces in order to use crooked line binning (if that's what we want to do).

What is now missing are CMP bin numbers and offset headers.

To decide how to do this, we need to plot out the shots and receivers on a diagram, perhaps via:

  suchart < data_with_geom.su key1=sx key2=sy >plotdata

  suchart < data_with_geom.su key1=gx key2=gy >>plotdata

This shows the SP and receiver locations on a chart. You can see these  locations with:

  xgraph <plotdata par=par linewidth=0,0 mark=8,2 marksize=2,2 n=70782,70782

You can also look at a vertical profile of the receiver line with:

     suchart < data_with_geom.su key1=gelev key2=gx >plotdata outpar=par;xgraph <plotdata par=par linewidth=0 mark=8 marksize=8

You can see that the receiver line has a big bend in it. The source line is very erratic, as somebody had to drive the vibe trucks where it was possible to do so. Walking the receivers was obviously a lot easier. The vertical profile shows that the topography was quite varied.

Because the line is far from straight, we can project the CMPs to the receiver line (the crooked-line strategy). Are there any other methods?

Regards

Glenn