The codes can run in Unix/Linux with Matlab 5.0, unfortunately, the Fortran
code 't4' does not support Matlab
6.0. All the Matlab files and Fortran codes are stored in directory
'openfile', since the Matlab 'startup.m' can
only set path for Matlab M files, all executable Fortran codes and
their input data files should be put into current work directory.
During installation, after you have copied all the files into your computer, You must do following before you can start the work:
If you use Unix, it might be enough. Run Matlab5 in 'openfile', then load 'xmain'. You can start to play with it. But to make sure all the Fortran executable codes can run in your machine safely, you should:
t4_sun | ----> t4 | for big endian machines (SUN) |
t4_pc | ----> t4 | for little endian machines (PC) |
A. Load Data
B. Display Data
C. Preprocess Data
D. Pick data
E. QC Data
F. Invert Data
G. Forward Modeling
H. Documentation
I . Quit GUI
In this lab, you only need to use "Invert Data " button, click on it and click on the choice "Units in meters". The interface for inversion will be loaded.
Clicking on the "Quit GUI " button will close all the interface.
2. Inversion Interface
This interface includes several menu choices, let go through
one by one:
(1) Dynamic Schedule:
Interactive module for dynamic smoothing schedule for the inversion. (From
large scale smoothing
to small size smoothing based on idea of resolving large scale structure
first, then dealing with fine
structure. Dynamic smoothing allows a balance between under-smoothed and
over-smoothed
tomograms in traveltime tomography). You can set up to 8 smoothing
schedules.
Parameters for each page of the schedule setting ( You can click on "help"
button for the information)
Iteration | Number of iteration for each smooth schedule. |
Grid spacing | Grid size for forward problem. |
Vtop | Velocity for the top of initial model in inversion. |
Vbottom | Velocity for the bottom of the initial model. |
Vmin | Estimated minimum value of velocity allowed in inversion. |
Vmax | Estimated maximum value of velocity allowed in inversion. |
Nite | Number of shots used to calculate the step length. |
Ndown | =1, downward extrapolation of gradient;
=2, downward extrapolation of slowness. |
Irsx | Number of grid involving in smoothing in x (horizontal) direction. |
Irsz | Number of grid involving in smoothing in x (horizontal) direction. |
(3) Show input data:
Plot travel time curve (t-x) and shot-receiver geometry in CSG.
(4) Starting model:
Show initial model will be used in the inversion code:
model 1 (Gradient model if Vtop);
model 2 (homogeneous with v=Vtop);
model 3 (homogeneous with v=Vbottom).
where Vtop, and Vbottom are from the smoothing schedule.
(5) Start inversion:
Run inversion Fortran code "refra-2d-pq.f".
submenu:
From beginning: Run inversion from scratch;
Continue...:
Continuing the calculation from the results got before.
Note: If you changed "coord.temp" during the inversion, you have to run inversion from beginning to honor the new geometry in the "coord.temp".
(6) Show Results:
Showing the inversion results such as velocity model, residual, and histogram
of the residual distribution.
submenu:
Velocity Field | Final result: Final result of velocity with raypaths.
Dynamic result: Velocity field for every smooth schedule. |
Histogram | Final result: Histogram of final residuals of traveltime.
Dynamic result: Histograms of residuals for every smooth schedule. |
Total Traveltime Residual | Behavior of residuals of traveltimes with respect to the number of iterations. |
(8) Save Figure
Save figures using Matlab "print" function.
(9) Close Figure
(10) Zoom, Zoom off, Zoom out
Zoom the figures, same as Matlab commands.
(11) Quit: Quit Inversion Interface