OCTAVE SASW.m - Select 2 traces from bsegy data set, compute dispersion by SASW from X-cor
SASW prompts for:
BSEGY file name
(*.seg) (shell terminal input)
Plot Settings: fmin, fmax, vmin, vmax (GUI entry box)
POPUP GUI
File name, Number traces, tmax, sample interval dt, dx,
Recommended Max. Trace Spacing
Tmax, Trace Selection R1, R2 (R2-R1 should not exceed
recommendation above) (GUI Entry Box)
SASW is Spectral Analysis of Surface Waves. Only requires source and two geophones.
Basic Seismic Utilities (BSU) program run in Octave or Matlab. Within an octave session, type SASW and then on prompt, enter the bsegy format file name (example: 1001.seg). The plot setting GUI is for display purposes, and the defaults are what one might expect useful on the typical soil profile with a hammer source. The PopUp GUI makes a recommendation on the maximum spacing between the selected far and near traces. For example, assume a 24 trace record with a R2-R1 recommendation not exceeding 1 trace. Then R1=1 and R2=2 or R1=10 and R2=11 would both be within the recommended spacing. The code takes care of which one is near and which one is far, so you need not worry.
COMMENT: Don’t push it with too large a spacing between traces, or too high a fmax. Also, fmin should be realistic for the source employed. The estimate is for a 1D soil profile directly below the two receivers. One can get a sense of 2D variation by selecting a number of trace pairs on a MASW type survey for example.
The differences between SASW.m and saswv.m are in the source and type of data. SASW.m reads two time domain recorded signals from a single file while saswv.m reads measured cross-power spectra and coherence. Thus, SASW.m must compute the cross spectra and coherence where as saswv.m uses measurements of those properties.
Figure 1 Cross
Power Spectrum and Coherence
Figure 2 Phase velocity frequency dispersion and coherence
estimate over selected range.
segyinfo.m
bsegin.m
OCTAVE: segyinfo.m(7) bsegin.m(7) saswv.m(7)
No known bugs.
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]>