colorwell.m

地震中常用的一些偏移程序

function [cop,tcop]=colorwell(r,t,n,l,op_length,fparms)

% [cop,tcop]=colorwell(r,t,n,l,op_length,fparms)
% [cop,tcop]=colorwell(r,t,n,l,op_length)
% [cop,tcop]=colorwell(r,t,n,l)
% [cop,tcop]=colorwell(r,t,n)
% [cop,tcop]=colorwell(r,t)
%
% COLORWELL designs a convolutional minimum phase operator which
% can be applied to the output of any spiking decon to correct
% for a non-white reflectivity.
%
% cop= output color operator
% tcop= time coordinate vector for cop 
% r= well log reflectivity series whose amplitude spectrum shows the expected 
%    non-white behavior
% t= time coordinate for r
% n= order of the polynomial approximation to the spectrum
%  ***************** default=3 ************
% l= Burg prediction filter length to be used in obtaining the
%    smoothed spectrum of r. The smaller l is, the smoother the
%    spectral color estimate.
%  ***************** default = 10 *************
% op_length= length (in seconds) of the desired operator
%  **************** default = .2 ***************
% fparms= 2 element vector of antialias filter parameters
%         fparms(1)= 3db down point of high frequency rolloff
%                    expressed as a fraction of the new nyquist
%         fparms(2)= attenuation desired at the new Nyquist in db
% *************** default = [.6,120] *******************
%
% NOTE: It is illegal for you to use this software for a purpose other
% than non-profit education or research UNLESS you are employed by a CREWES
% Project sponsor. By using this software, you are agreeing to the terms
% detailed in this software's Matlab source file.
 
% BEGIN TERMS OF USE LICENSE
%
% This SOFTWARE is maintained by the CREWES Project at the Department
% of Geology and Geophysics of the University of Calgary, Calgary,
% Alberta, Canada.  The copyright and ownership is jointly held by 
% its author (identified above) and the CREWES Project.  The CREWES 
% project may be contacted via email at:  [e-mail]
% 
% The term 'SOFTWARE' refers to the Matlab source code, translations to
% any other computer language, or object code
%
% Terms of use of this SOFTWARE
%
% 1) Use of this SOFTWARE by any for-profit commercial organization is
%    expressly forbidden unless said organization is a CREWES Project
%    Sponsor.
%
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 specop=0; Sdb=0;
 if nargin<6, fparms=[.6,120]; end
 if nargin<5, op_length=.2; end
 if nargin<4, l=10; end
 if nargin<3, n=3; end
  
% compute the number of spectral points needed
	dt=t(2)-t(1);
 op_length=op_length/dt+1;
 op_length=2^nextpow2(op_length);
 [a,b]= fftrl(ones(1,op_length),t);
 nop=length(a);
% compute the burg amplitude spectrum
 [specb,fb]= burg(r,t,l,nop);
% invoke interactive polynomial fitting
 [specop,coeff]=visifit(todb(specb),fb,n);
 specop=fromdb(specop,max(specb));
% multiply by an antialiasing filter
 fn=.5/dt;
 fmax=[fparms(1)*fn,.3*fn*(1-fparms(1))];
 [fltr,fop]=filtspec(ones(1,op_length),t,[0,0],fmax,0,fparms(2));
 specop=specop.*fltr;
% compute the minimum phase time domain operator
 [cop,tcop]= minwave(specop,fb);