Subject
Reading
HW1
Chapters
1-3
Basic reflection
seismic acquisition
and processing
Kallweit
and Wood
(1982)
Homework
A. Do the following exercises
1.4, 1.9, 1.10, 1.11, 1.12
2.2, 2.7, 2.8, 2.10, 2.11, 2.12, 2.13
The shot file for exercises 2.10-2.13 is ozdata.25. It is already
downloaded and in SU format so you need only input it into an SU module,
i. e.
Fourier analysis
Equations of motion
and the wave
equations
%suxwigb < $DATA/ozdata.25 perc=99
If you process this shot and want to save the results make sure you save
them in your data directory, not in your home directory.
Answers
B. Study the shell script fresnel. Run it and observe how the maximum
amplitude of the reflected wave increases and then decreases as the length of
the reflector segment is increased. Based on the output what do you expect
the size of the Fresnel Zone to be? Compare this with the theoretical size.
HW2
Wave equation
properties
Chapters
4-6
Schneider
(1978)
Ray theory
A. Do the following exercises
4.1, 4.2, 4.4
5.1, 5.2
6.1
Kirchhoff migration
B. A synthetic data set (99 shots and 100 channels) along a 10 km long
profile has been generated and the shot gathers are stored in HW_data.su.
Process these data to a stacked section using the processing strategy outlined
in exercise 3.2. Note that the geometry (sx and gx in decimeters, not meters)
has already been defined so you can skip this step. Furthermore, the shot
spacing is 100 m and the receiver spacing is 25 m. Note also that the data
contain noise and require some filtering to be applied. It is this stacked
section you will later be applying your migration routine to.
Answers
To look at a single shot gather in the middle of the profile you can use the
following command
%suwind key=sx max=0 accept=50025 tmax=4 < $DATA/HW_data.su | sugain tpow=1 | suxwigb d2=1
verbose=1 perc=98
A. Do the following exercises
HW3
Chapters
Other migration
methods
8.3
Deregowski (1986)
9.1, 9.2
7-9
Subject
Reading
Homework
Dip moveout (DMO) Temme
Note the error in 8.3 for g(x). g(x) should be
Answers
g(x)=exp{­x2}
(1984)
B. Study section 9.10 and think about how to implement a 2D Kirchhoff
migration routine.
HW4
Chapters
10-12
A. Program the 2D Kirchhoff migration algorithm below
Spherical waves and
plane wave
decomposition
Numerical methods
into the su_my_mig.c module. Assume straight rays in calculating the
traveltimes. However, the velocity may vary spatially.
is the angle
between the vertical and the ray path from the image point to the surface
observation. The length of the ray path is r.
First program the code without using the half-derivative. After you are
confident that the migration is working correctly then attempt to apply the
half-derivative to the stacked section prior to migration. The half-derivative
operator only affects the phase of the output section.
The module is set up so that you all you need to add is the algorithm. Copy
the module and Makefile from the to your home directory.
To compile you need to do
%make su_my_mig
This will compile your code, link it and put the object code into your /home/username/bin directory. If it is the first time you compile and link
then you will need to source your bin directory with
%source ~/.cshrc
Please contact me if you have any problems.
If you absolutely do not want to program in C you may use MATLAB. Note
that the MATLAB code will be much much slower since the algorithm
requires loops. You must also import and export the SU data files into
MATLAB in order to test the migration code. I have MATLAB scripts
that read and write SEGY files if you need them.
B. Apply the above migration routine to the stacked section you
produced in the second homework and compare your migration with
the SU Gazdag migration. Which one is best?
Where relevant your work should be handed in as shell scripts.