SUHARLAN - signal-noise separation by the invertible linear
transformation method of Harlan, 1984
susnlinsep outfile [optional parameters]
Required Parameters:
Optional Parameters:
FLAGS:
niter=1 number of requested iterations
anenv=1 =1 for positive analytic envelopes
=0 for no analytic envelopes (not recommended)
scl=0 =1 to scale output traces (not recommended)
plot=3 =0 for no plots. =1 for 1-D plots only
=2 for 2-D plots only. =3 for all plots
norm=1 =0 not to normalize reliability values
verbose=1 =0 not to print processing information
rgt=2 =1 for uniform random generator
=2 for gaussian random generator
sts=1 =0 for no smoothing (not recommended)
tmpdir= if non-empty, use the value as a directory path
prefix for storing temporary files; else if the
the CWP_TMPDIR environment variable is set use
its value for the path; else use tmpfile()
General Parameters:
dx=20 offset sampling interval (m)
fx=0 offset on first trace (m)
dt=0.004 time sampling interval (s)
Tau-P Transform Parameters:
gopt=1 =1 for parabolic transform. =2 for Foster/Mosher
=3 for linear. =4 for absolute value of linear
pmin1=-400 minimum moveout at farthest offset for fwd transf(ms)
pmax1=400 maximum moveout at farthest offset for fwd transf(ms)
pmin2=pmin1 minimum moveout at farthest offset for inv transf(ms)
pmax2=pmax1 maximum moveout at farthest offset for inv transf(ms)
np=100 number of p-values for taup transform
prewhite=0.01 prewhitening value (suggested between 0.1 and 0,01)
offref=2000 reference offset for p-values (m)
depthref=500 reference depth for Foster/Mosher taup (if gopt=4)
pmula=pmax1 maximum p-value preserved in the data (ms)
pmulb=pmax1 minimum p-value muted on the data (ms)
ninterp=0 number of traces to interpolate in input data
Extraction Parameters:
nintlh=50 number of intervals (bins) in histograms
sditer=5 number of steepest descent iterations to compute ps
c=0.04 maximum noise allowed in a sample of signal(%)
rel1=0.5 reliability value for first pass of the extraction
rel2=0.75 reliability value for second pass of the extraction
Smoothing Parameters: ",
r1=10 number of points for damped lsq vertical smoothing
r2=2 number of points for damped lsq horizontal smoothing
Output Files:
signal=out_signal name of output file for extracted signal
noise=out_noise name of output file for extracted noise
Notes:
The signal-noise separation algorithm was developed by Dr. Bill Harlan
in 1984. It can be used to separate events that can be focused by a
linear transformation (signal) from events that can't (noise). The
linear transform is whatever is well siuted for the application at
hand. Here, only the discrete Radon transform is used, so the program
is capable of separating events focused by that transform (linear,
parabolic or time-invariantly hyperbolic). Should other transform be
required, the changes to the program will be relatively
straightforward.
The reliability parameter is the most critical one to determine what
to extract as signal and what to reject as noise. It should be tested
for every dataset. The way to test it is to start with a small value,
say 0.1 or 0.01. If too much noise is present in the extracted noise,
it is too low. If too much signal was extracted, that is, part of the
signal was lost, it is too big. All other parameters have good default
values and should perhaps not be changed in a first encounter with the
program. The transform parameters are also critical. They should be
chosen such that no aliasing is present and such that the range of
interesting slopes is spanned by the transform but not much more. The
program suradon.c has more documentation on the transform paramters.
Credits:
Gabriel Alvarez CWP (1995)
Some subroutines are direct translations to C from Fortran versions
written by Dr. Bill Harlan (1984)
References:
Harlan, S., Claerbout, J., and Roca, F. (1984), Signal/noise
separation and velocity estimation, Geophysics, v. 49, no. 11,
p 1869-1880.
Harlan, S. (1988), Separation of signal and noise applied to
vertical seismic profiles, Geophysics, v. 53, no. 7,
p 932-946.
Alvarez, G. (1995), Comparison of moveout-based approaches to
ground roll and multiple suppression, MSc., Department of
Geophysics, Colorado School of Mines, (Chapter 3 deals
exclusively with this method).