thaper.m

Univ. of Calgary CREWS的免费地震研究软件

function theta = thaper(a,vo,c,z)
% THAPER: compute aperture-limited scattering angle versus depth
%
% theta = thaper(a,vo,c,z)
%
% Compute the zero offset scattering angle limit imposed
% by recording aperture.
%
% a ... aperture
% vo ... initial velocity
% c ... accelerator ( v(z) = vo +c*z )
% z ... vector of depths for which theta is computed
% theta ... vector of limiting scattering angles. One for each z.
%
% G.F. Margrave, CREWES, 1997
%
% 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.
%
% 2) A CREWES Project sponsor may use this SOFTWARE under the terms of the 
%    CREWES Project Sponsorship agreement.
%
% 3) A student or employee of a non-profit educational institution may 
%    use this SOFTWARE subject to the following terms and conditions:
%    - this SOFTWARE is for teaching or research purposes only.
%    - this SOFTWARE may be distributed to other students or researchers 
%      provided that these license terms are included.
%    - reselling the SOFTWARE, or including it or any portion of it, in any
%      software that will be resold is expressly forbidden.
%    - transfering the SOFTWARE in any form to a commercial firm or any 
%      other for-profit organization is expressly forbidden.
%
% END TERMS OF USE LICENSE

if( c ~= 0)
	gamma = vo./(vo+c*z);
	
	top = ( 2*a*c*vo*gamma).^2;
	term=(a*a*c*c +vo*vo)^2;
	term2=(a*a*c*c - vo*vo);
	bot = term*gamma.^4 + 2*term2*(vo*gamma).^2 + vo^4;
	
	snth = sqrt(top./bot);
	theta=180*asin(snth)/pi;
	
	%test for theta or 180-theta
	csth = sqrt(1-snth.^2);
	atest = vo*(sqrt(1-(gamma.*snth).^2)-csth)./(c*gamma.*snth);
	ind = find( abs(atest-a)/a > 10^(-6));
	theta (ind) =180- theta(ind);
else
	ind= z==0;
	theta=zeros(size(ind));
	theta(~ind) = 180*atan(a./z(~ind))/pi;	
	theta(ind) = 90*ones(sum(ind),1);
	
end