1. 12.12.2007
Data Analysis for Refraction Tomography
Data Conversion
Killing Signal
Picking Approaches
SeisOptPicker
Model Geometry y
Senior Project-Geop402
Dr.Ali o.Oncel
First Break Picking Module
4 copy of SeisOptPicker is uploaded to PC in Computer Lab of ESD.
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2. 12.12.2007
Data Conversion
MAKE SURE you name the converted SEG2 files sequentially. That is, name them
P1_S01, P1_S02 etc (see above showed SEG-2 files). If you do this, you can be sure
that the SU file will also show the shots in sequence. Otherwise you will see shot 1 first
then shot10 11, and so on
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3. 12.12.2007
Some Pitfalls and Solution
• Differences in the Recording Length can
cause such ki d of diff
h kind f differences. Th
Thus, one
is asked to checked.
• Recorded Length for first data is 2 ms
while others have a shorter record length,
which is 1.5 ms.
• Solution: Ignore those data having
different length and later combine.
Header Edit
This year, we have recorded 96 traces with 3D geophones, kept 32 of those and deleted
other horizontal components based traces (64). Then, Header Edit is required to fix
Header Size to number of data. This is an example for converted data from SEG2 to
SU.
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4. 12.12.2007
Header Edit
TRACF
Enter values as
E t l
1,2,3,4,5,…….32
Senior Project-Geop402
Data Conversion
Killing Signal
Picking Approaches
SeisOptPicker
Model G
M d l Geometry t
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8. 12.12.2007
Compare Traces: How it worked well?
Selected Traces by INTERPEX by component
Traces by TSPRO by one to one deleting signals.
CONVERT FILE to SEG-2
From what I have experienced, If click EXPORT SEG2, it may not
be read by other programs in case one modified the data
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10. 12.12.2007
Seismic
Record
First b k
Fi break
First departure
First Kick
Time
Source: Lie, M., 2000, , Master Thesis, University of Sydney.
Corrections on Seismic Record
No DC Shift DC Shift
Well-known seismic software
has such kind of tool to make a
correction.
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11. 12.12.2007
Manually Picking
Consistency is very
important for manually
picking. Then, it is better
to select one model of
picked seismic waves.
Source: Lie, M., 2000, Seismic Applications of Interactive Computational Methods, Master Thesis, University of Sydney.
One Approach for Manually Picking
Model Signal
is assigned as a Reference
Signal and kept as a fixed.
Selected signal
There is no matching since time
delay due to changes in
distance makes a changes in
waveform overlapping.
Overlapping signal
Signals are overlapped and same
location as picked on reference
signal is aimed to pick. The
similarity between two signals are
given by value of ratio as As/Ar.
One Approach for Manually Picking Signal Such option you can find under the
program of TSPRO. Visit to class page.
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12. 12.12.2007
Automated Picking Methods
I suggest you to read a couple of papers for picking
First Arrivals since it is an important part of data
preparation. A couple of papers you can easily find:
http://scitation.aip.org/geophysics/
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15. 12.12.2007
Truncate Traces: Enlarging Signal
I have cut the signals for time larger than 125 Milliseconds since First Arrivals
were appeared before.
Trace Plotting Parameters
Automated Gain Control is nice option to strength the signal which can be easily
detected.
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17. 12.12.2007
Picked Examples
Picking Experiences: Clean Record 70
60
Time (ms)
50
40
30
T
20
10
0
0 5 10 15 20 25 30 35
60
50
40
s)
Time (ms
30
20
10
0
0 5 10 15 20 25 30 35
The clear data makes picking arrivals easy and observed slight differences on picked
data made by two different person.
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18. 12.12.2007
Picking Experiences: Noisy Record
100
90
80
Tim (ms)
70
60
50
me
40
30
20
10
0
0 5 10 15 20 25 30 35
Distance (meter)
90
80
s) 70
60
Time (ms
50
40
30
20
10
0
0 5 10 15 20 25 30 35
The noisy data makes picking arrivals difficult and observed slight differences on
picked data made by two different person.
Picked Examples on Good Records
70
70
60 60
50 50
Time (ms)
Time (ms)
40 40
30 30
20 20
10 10
0
0
0 10 20 30 40
0 10 20 30 40
Distance (meter) Distance (meter)
It is an average data makes picking arrivals easier than noisy data.
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19. 12.12.2007
Concluded Remarks
• It seems that Hatherly Picking Technique
makes a good job for initial picking but it is
better to check one to one for each signal.
• Filtering is difficult for areas of higher noise
since following filtering data is out, one faces
up another noise of different frequencies.
• Traces Plotting Parameter for example AGC
Parameter, AGC,
provides strength traces
• Noisy data requires a significant time to find
true picked values of arrival times.
Senior Project-Geop402
Data Conversion
Killing Signal
Picking Approaches
SeisOptPicker
Model Geometry
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21. 12.12.2007
RECORD 1 Click here to
PS_01 see next record
RECORD 2 Traces are also
consecutively
PS_02 shown.
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22. 12.12.2007
RECORD 13 Traces are also
consecutively
PS_13 shown.
Factors Affecting Arrival Times
2006-2007: We had records on material with relatively fast
velocities through Profile1 which is only about 10m. So the
arrival times appeared to be very small Unfortunately the
small. Unfortunately,
resolution of the traces became poor (lower frequency).
Because sample interval of seismic interval was smaller than
0.25 milliseconds, due to old instrument,.
2007-2008: We made seismic survey with state of art
seismometer which provided high quality of records with
0.125 milliseconds. Now, we could see better resolution of
these picks.
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23. 12.12.2007
PICKING DATA
Zoomed in
Window time display
Type 50 ms
Set trace size=20
Window time display
No equalization
Clip amplitude
I used the tool "zoomed in" to the top part of the traces for picking You do this
by selecting "window time display" under the "Display option" menu. Type in 50
(for 50 milliseconds) and the top 50 milliseconds will be shown. You can see the
first-break clearer now.
I also set trace size to 20 (top left scroll bar all the way to the right). I
selected "No equalization" under Display Option->Trace Equalization and
Selected "Clip Amplitude" also.
Saving Pick File
Next step is the
enter geometry.
After picking all the traces, make sure to click "Save FBP" button. This will turn the red
picks to blue color. I tried auto picking but gave up since it doesn't work well for this
data. I picked each trace manually the best I could. You will notice all the picks are
almost same arrival time –
Once again so to say, it is a combination of short distances and the sampling rate
used not being high enough.
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25. 12.12.2007
S_13 S_01
9.9 M
S_12 S_11 S_10 S_09 S_08 S_07 S_06 S_05 S_04 S_03 S_02
G_1 G_2 G_3 G_4 G_5 G_6 G_7 G_8 G_9 G-10 G_11 G_12
Shots Data Distance (m)
Shot X and Firs Receiver
t
S_1 P1_01 10.35
4.5 m S_2 P1_02 9.45
S_3 P1_03 8.55
S_4 P1_04 7.65
S_5 P1_05 6.75
S_6 P1_06 5.85
S_7 P1_07 4.95
S_8 P1_08 4.05
S_9 P1_09 3.15
S_10 P1_10 2.25
0.0m S_11 P1_11 1.35
9.9m
S_12
S 12 P1_12
P1 12 0.45
0 45
S_13 P1_13 -0.45
First Receiver X = 0.0
Shot X = 10.35 Receiver Spacing= 0.9 m
Shot Spacing= -0.9 m
S= Shoot location
G= Geophone location
Shot 13 Profile Geometry Shot 1
"Record SHot" before going to "Next
Make sure First Receiver X = 0.0 Record”. And, make sure the receiver
spacing is changed to 0.9 and check the
Shot X for “Shot 1” is 10.35
coordinates in the row below.
Shot X for “Shot 13” is -0.45
Things seems working on the Model
Geometry regarding the Off-profile
Shot Locations
Now, check it again by touching “?”, then exit .
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26. 12.12.2007
Save and Export
Following the tasks of entering the data for profile geometry and picking the data of first
arrival, then it is time to save and export the file for SEIS-OPT for constructing 2D
model of refraction velocity.
Data Control
Show files
The data is ready for a final check before saving Check it clearly till you are satisfied
saving.
with the entered data on their correctness since the present data is input for modeling
software of refraction velocity (Seis-OPT). Then, Save Pick Files if nothing seems
wrong.
That is a final reminder for data. If it is
true, click “Save SeisOptPick files” and then
“Show files”.
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27. 12.12.2007
S= Display Shot F= Display First break
Coordinates time (s) G= Display Receiver X and Z
Check the file for each of above those inputs, the Save them individually under the FILE.
Then, you are suggested to open saved files one more time from where the files are
saved. If files on data are saved truly, now it is time to work with the other program
(Seis-OPT) for modeling 2D velocity.
Problem: Missing Data
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28. 12.12.2007
Suggestions
What you do is click "Yes" in the dialog box
that
th t asks "Fi ld number missing correct
k "Field b i i t
now". Then you enter "1" when it asks
enter first field id number. Click ok. The
first time you will see empty box in the
export window as in slide 2. Do the export
again and now you should see the values
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