bamx - BSU measure surface wave inelastic amplitude decay as a function of frequency
bamx [ -h | infile | rmin | rmax | fmin | fmax | delf | bw | tmax ]
Basic Seismic Utilities (BSU) measures inelastic amplitude decay (corrected for cylindrical divergence). Assumes that the data are from a shot gather which has not had any gain processing beyond recorded gain recovery. Program creates an output file, bamx.his Requires either plplot shared library or GNUPLOT if postscript plots to be produced. PLPLOT is a GNU function/subroutine library which can generate PostScript plots (http://plplot.sourceforge.net). GNUPLOT can be downloaded from https://sourceforge.net/projects/gnuplot. One may compile for either PLPLOT or GNUPLOT, but not both.
Options
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-h |
Online help giving details on command line arguments | ||
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infile |
Input file name | ||
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rmin |
Minimum geophone range to include in the analysis zone. | ||
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rmax |
Maximum geophone range to include in the analysis zone. | ||
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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. One should not try to exceed the resolution implied by the recording aperture. Thus, delf should not be less than 1/(npts*fsamin), where npts is the number of samples in the trace, fsamin is the sample interval. Or put another way, be sure to record enough data to permit adaquate resolution in the frequency domain. | ||
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bw |
Bandwidth of the filters. See comment above on resolution. | ||
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tmax |
Maximum time to scan. Note: If the data have been aligned on the first arrivals, tmax will mark the time after the first arrival. See programs bpic and bshf. |
NOTE:
If invoked with no options, will prompt user for input
parameters.
EXAMPLE:
bamx data.seg 1. 100. 6.0 100.0 2.0 2.0 .5
Input file data.seg is processed for the surface interval between source-receiver offset 1.0 m (near) and 100.0 m (far). 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 and the input data window extends to 0.5 seconds.
bamx.ps
Summary Postscript plot of amplitude decay (nepers/m) as a function of frequency.
bamxqc.ps
QC Postscript plot of amplitude decay as a function of range for each frequency.
bamx.his
Text file of frequency (hz), amplitude decay (nepers/m), standard deviation of decay.
bamxdb.his
Text file of frequency (hz), amplitude decay (decibels/m), standard deviation of decay.
bamx.gp
Gnuplot script text file that generates bamx.ps
bamxqc.gp
Gnuplot script text file that generates bamxqc.ps
bamxxxxx.lst
Listing file for bamx. The characters, xxxx, will be the first 4 char of the input file name (for example, would be data).
standard output
list of frequency, decay (dB/m should be <0), decay (nepers/m, should be >0)
bhelp(1), bvax(1)
No known bugs. In cases of noisy data, or a thin zone of analysis, one may obtain decay values suggesting an increase in amplitude with propagation distance (dB/m>0). The code fixes such cases to zero decay in the history file. Increasing the zone thickness (rmax-rmin) or limiting the scan of frequencies to those with the best signal to noise will reduce the number of zero fixed values. When examining bamxqc.ps, good results correspond to negative decay values (sloping down with increasing frequency). Results which slope upward with increasing range are in conflict with the basic model, and are zeroed in the bamp.his file as mentioned above.
Copyright © 2021 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]>