Program cafwd3.m is a Octave program which permits one to compute the velocity
dispersion and amplitude decay as a function of frequency. Given user supplied values
for stiffness ( in
) and damping (
in
), the program computes
frequency dependent phase velocity dispersion (
) and decay (
). A second plot
re-expresses the amplitude decay as a quality factor, Q. This is computed
by (Toksöz (22) )
![]() |
(19) |
where is the decay in units of
,
is frequency, and
is velocity at
that frequency. There are two ways to use the program.
To run the program, start a Octave session. Then, inside the interactive Octave text window, type:
cafwd3
With the first GUI, choose if data are to be included in the plot.
If data are included, you will be prompted to use the mouse to select a frequency
range to model. For the non data case, the frequency range is hardwired, and can be changed if
needed by editing the program (look for fmin and fmax variables at the top). The program will
do an initial case on its own. If there are data, it will look at the data and make a reasonable
first guess. If there are no data, a default GUI will come up. One can then change the values for
stiffness and damping and recalculate a new set of plots. Figure 25 shows examples of
the two ways dispersion can be presented (ie. with or without data plots). One can keep revising
the values and clicking OK as much as one wants. When done, click the ``cancel'' button. An example
of the second Q-plot is shown in Figure 26. This corresponds to the run shown
in Figure 25A. Note that the example values for and
are different for the no data and with data cases.
pm 2018-04-17