bvas - BSU measure velocity dispersion of body waves
bvas [ -h | infile | emin | emax | vmin | vmax | nvel | fmin | fmax | delf | bwd | iskip | ivscn ]
Basic Seismic Utilities (BSU) measures velocity as a function of frequency for a body wave as observed in a Vertical Seismic Profile (VSP). Outputs include a history file, bvas.his, which records the velocity and standard deviation in velocity for each frequency. The file bvas.his can be used with bamp.his (see BAMP) in a joint inversion for the two inelastic wave equation coefficients (stiffness and damping) under the Kelvin constitutive model. The depth zone to be analysed is specified by the elevation headers. Requires plplot shared library if postscript plots to be produced. PLPLOT is a GNU plotting subroutine/function library (http://plplot.sourceforge.net).
Options
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-h |
Online help giving details on command line arguments | ||
|
infile |
Input file name | ||
|
emin |
Minimum geophone elevation to include in the analysis zone. | ||
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emax |
Maximum geophone elevation to include in the analysis zone. | ||
|
vmin |
Minimum velocity for the scan. | ||
|
vmax |
Maximum velocity for the scan. | ||
|
nvel |
Number of velocities in the scan. | ||
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fmin |
Minimum frequency for the scan. | ||
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fmax |
Maximum frequency for the scan. | ||
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delf |
Frequency increment for the scan. See resolution comment for bwd. | ||
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bwd |
Bandwidth of the filters. Do not try to exceed the resolution implied by the recording aperture. Thus, bwd should not be less than 1/(npts*fsamin), where npts is the number of samples in the trace, fsamin is the sample interval. | ||
|
iskip |
(-1=NO), do not skip filter step, and to save disk space, delete each bvasxxxx.seg when done. |
0=NO, do not skip filter, data
sets bvasxxxx.seg do not
exist in directory.
1=YES, skip filter step (assumes previously run and data
sets saved as bvasxxxx.seg)
|
ivscn |
0=NO, do not save the velocity scan waveform panels |
1=YES, do save the velocity
scan waveform panels (CAUTION:
this could be a very big file)
NOTE:
If invoked with no options, will prompt user for input
parameters.
EXAMPLE:
bvas twave.seg 840.45 843.60 100. 2000. 40 6. 100. 2. 2. 0
0
Input file twave.seg is processed for the subsurface interval between elevations 840.45 m (bottom) and 843.6 m (top). The minumum velocity scanned will be 100 m/s, the maximum velocity will be 2000 m/s. The velocity scan will be made in 40 steps. The minimum frequency scanned will be 6 Hz, the maximum frequency scanned will be 100 hz. The frequencies will be scanned every 2 Hz (thus center frequencies scanned are 6, 8, 10, ... to 100 Hz). The bandwidth of each filter is 2.0 hz. Don’t skip filtering the data (first time run) and don’t write a velscn file (that would provide too many pannels with a 40 velocity step scan).
bvas.ps
Summary Postscript plots of velocity and semblance as a function of frequency.
bvasqc.ps
QC Postscript plot of time shifts as a function of elevation for each frequency (computed from cross correlations).
bvas.his
Text file of frequency (hz), phase velocity (m/s), standard deviation of velocity.
semblance.dat
Data file with (frequency, velocity, semblance) triplets. This file is formatted for input into the Gnuplot generated scripts.
CLRplot.gp
Gnuplot script plots semblance image for (frequency,phase velocity) space. Colors correspond to semblance value. This script is also run during the run of bvas.F90, creating the image clrplot.png.
CNTplot.gp
Gnuplot script plots semblance image for (frequency,phase velocity) space. Image is a contour plot with contours that correspond to semblance value. This script is also run during the run of bvas.F90, creating the contour plot image cntplot.png.
GRYplot.gp
Gnuplot script provides a gray scale image. Script not run by bvas.F90, that would be up to the user. Type gnuplot to open a gnuplot shell. Then ’load GRYplot.gp’ will start an interactive plot.
MSHplot.gp
Gnuplot script provides a mesh type image. Script not run by bvas.F90, that would be up to the user. Type gnuplot to open a gnuplot shell. Then ’load MSHplot.gp’ will start an interactive plot.
bvasxxxx.seg
If iskip=0, saves filtered, trace equalized data (all elevations). The frequency is encoded in the file name as the xxxx suffix.
vscnxxxx.seg
If ivscn=1, saves filtered velocity scan panels. CAUTION: This can produce an VERY large file. HIGHLY RECOMMEND that nvel=5 or some small number if you do this. The name of the file has the frequency encoded with the xxxx suffix.
bvasxxxx.lst
Listing file for bvas. The characters, xxxx, will be the first 4 char of the input file name.
standard output
list of frequency, velocity, std. dev., semblance, and number of steps in golden section search.
bhelp(1), bamp(1)
No known bugs. In cases of noisy data, or a thin zone of analysis, or a poor choice of scan limits, the semblance may not peak. In that case, the code skips that frequency and moves on. It is also possible to have multiple peaks if aliasing occurs. It is the responsibility of the user to avoid spatial aliasing and QC the listing file, bvasxxxx.lst.
Copyright © 2024 by Paul Michaels
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
P. Michaels, PE. <[email protected]>