SURADON - compute forward or reverse Radon transform or remove multiples
by using the parabolic Radon transform to estimate multiples
and subtract.
suradon stdout [Optional Parameters]
Optional Parameters:
choose=0 0 Forward Radon transform
1 Compute data minus multiples
2 Compute estimate of multiples
3 Compute forward and reverse transform
4 Compute inverse Radon transform
igopt=1 1 parabolic transform: g(x) = offset**2
2 Foster/Mosher psuedo hyperbolic transform
g(x) = sqrt(depth**2 + offset**2)
3 Linear tau-p: g(x) = offset
4 abs linear tau-p: g(x) = abs(offset)
offref=2000. reference maximum offset to which maximum and minimum
moveout times are associated
interoff=0. intercept offset to which tau-p times are associated
pmin=-200 minimum moveout in ms on reference offset
pmax=400 maximum moveout in ms on reference offset
dp=16 moveout increment in ms on reference offset
pmula=80 moveout in ms on reference offset where multiples begin
at maximum time
pmulb=200 moveout in ms on reference offset where multiples begin
at zero time
depthref=500. Reference depth for Foster/Mosher hyperbolic transform
nwin=1 number of windows to use through the mute zone
f1=60. High-end frequency before taper off
f2=80. High-end frequency
prewhite=0.1 Prewhitening factor in percent.
cdpkey=cdp name of header word for defining ensemble
offkey=offset name of header word with spatial information
nxmax=120 maximum number of input traces per ensemble
Optimizing Parameters:
The following parameters are occasionally used to avoid spatial aliasing
problems on the linear tau-p transform. Not recommended for other
transforms...
ninterp=0 number of traces to interpolate between each input trace
prior to computing transform
freq1=3.0 low-end frequency in Hz for picking (good default: 3 Hz)
(Known bug: freq1 cannot be zero)
freq2=20.0 high-end frequency in Hz for picking (good default: 20 Hz)
lagc=400 length of AGC operator for picking (good default: 400 ms)
lent=5 length of time smoother in samples for picker
(good default: 5 samples)
lenx=1 length of space smoother in samples for picker
(good default: 1 sample)
xopt=1 1 = use differences for spatial derivative
(works with irregular spacing)
0 = use FFT derivative for spatial derivatives
(more accurate but requires regular spacing and
at least 16 input tracs--will switch to differences
automatically if have less than 16 input traces)
Credits:
CWP: John Anderson (visitor to CSM from Mobil) Spring 1993
Multiple removal notes:
Usually the input data are NMO corrected CMP gathers. The
first pass is to compute a parabolic Radon transform and
identify the multiples in the transform domain. Then, the
module is run on all the data using "choose=1" to estimate
and subtract the multiples. See the May, 1993 CWP Project
Review for more extensive documentation.
NWIN notes:
The parabolic transform runs with higher resolution if the
mute zone is honored. When "nwin" is specified larger than
one (say 6), then multiple windows are used through the mute
zone. It is assumed in this case that the input data are
sorted by the offkey header item from small offset to large
offset. This causes the code to run 6 times longer. The
mute time is taken from the "muts" header word. Beware,
the SU mute module does not set this header word as one
would normally expect. You have to manually set it yourself.
References:
Anderson, J. E., 1993, Parabolic and linear 2-D, tau-p transforms
using the generalized radon tranform, in May 11-14, 1993
Project Review, Consortium Project on Seismic Inverse methods
for Complex Structures, CWP-137, Center for Wave Phenomena
internal report.
Other References cited in above paper:
Beylkin, G,.1987, The discrete Radon transform: IEEE Transactions
of Acoustics, Speech, and Signal Processing, 35, 162-712.
Chapman, C.H.,1981, Generalized Radon transforms and slant stacks:
Geophysical Journal of the Royal Astronomical Society, 66,
445-453.
Foster, D. J. and Mosher, C. C., 1990, Multiple supression
using curvilinear Radon transforms: SEG Expanded Abstracts 1990,
1647-1650.
Foster, D. J. and Mosher, C. C., 1992, Suppression of multiples
using the Radon transform: Geophysics, 57, No. 3, 386-395.
Gulunay, N., 1990, F-X domain least-squares Tau-P and Tau-Q: SEG
Expanded Abstracts 1990, 1607-1610.
Hampson, D., 1986, Inverse velocity stacking for multiple elimination:
J. Can. Soc. Expl. Geophs., 22, 44-55.
Hampson, D., 1987, The discrete Radon transform: a new tool for image
enhancement and noise suppression: SEG Expanded Abstracts 1978,
141-143.
Johnston, D.E., 1990, Which multiple suppression method should I use?
SEG Expanded Abstracts 1990, 1750-1752.
Trace header words accessed: ns, dt, cdpkey, offkey, muts