upweik.par.lib

su 的源代码库

UPWEIK - Upwind Finite Difference Eikonal Solver

eikpex - Eikonal equation extrapolation of times and derivatives in 
         polar coordinates
ray_theoretic_sigma - difference equation extrapolation of "ray_theoretic_sigma" in polar coordinates
ray_theoretic_beta - difference equation extrapolation of "ray_theoretic_beta" in polar coordinates
eiktam - Compute traveltimes t(x,z) and  propagation angle a(x,z) via 
         eikonal equation, and ray_theoretic_sigma sig(x,z), incident angle bet(x,z) 
         via Crank-Nicolson Method
Function Prototypes:
void eikpex (int na, float da, float r, float dr, 
	float sc[], float uc[], float wc[], float tc[],
	float sn[], float un[], float wn[], float tn[]);
void ray_theoretic_sigma (int na, float da, float r, float dr, 
	float uc[], float wc[], float sc[],
	float un[], float wn[], float sn[]);
void ray_theoretic_beta (int na, float da, float r, float dr, 
	float uc[], float wc[], float bc[],
	float un[], float wn[], float bn[]);
void eiktam (float xs, float zs, 
	int nz, float dz, float fz, int nx, float dx, float fx, float **vel,
	float **time, float **angle, float **sig, float **bet)
eikpex:
Input:
na		number of a samples
da		a sampling interval
r		current radial distance r
dr		radial distance to extrapolate
sc		array[na] of slownesses at current r
uc		array[na] of dt/dr at current r
wc		array[na] of dt/da at current r
tc		array[na] of times t at current r
sn		array[na] of slownesses at next r

Output:
un		array[na] of dt/dr at next r (may be equivalenced to uc)
wn		array[na] of dt/da at next r (may be equivalenced to wc)
tn		array[na] of times t at next r (may be equivalenced to tc)

ray_theoretic_sigma:
Input:
na		number of a samples
da		a sampling interval
r		current radial distance r
dr		radial distance to extrapolate
uc		array[na] of dt/dr at current r
wc		array[na] of dt/da at current r
sc		array[na] of ray_theoretic_sigma  at current r
un		array[na] of dt/dr at next r
wn		array[na] of dt/da at next r

Output:
sn		array[na] of ray_theoretic_sigma at next r 
ray_theoretic_beta:
Input:
na		number of a samples
da		a sampling interval
r		current radial distance r
dr		radial distance to extrapolate
uc		array[na] of dt/dr at current r
wc		array[na] of dt/da at current r
bc		array[na] of ray_theoretic_beta  at current r
un		array[na] of dt/dr at next r
wn		array[na] of dt/da at next r

Output:
bn		array[na] of ray_theoretic_beta at next r 
eiktam:
Input:
xs		x coordinate of source (must be within x samples)
zs		z coordinate of source (must be within z samples)
nz		number of z samples
dz		z sampling interval
fz		first z sample
nx		number of x samples
dx		x sampling interval
fx		first x sample
vel		array[nx][nz] containing velocities

Output:
time		array[nx][nz] containing first-arrival times
angle		array[nx][nz] containing propagation angles
sig  		array[nx][nz] containing ray_theoretic_sigmas
bet		array[nx][nz] containing ray_theoretic_betas
Notes:
eikpex:
If na*da==2*PI, then the angular coordinate is wrapped around (periodic). 

This function implements the finite-difference method described by Bill
Symes (Rice University) and Jos van Trier (Stanford University) in a
(1990) preprint of a paper submitted to Geophysics.

ray_theoretic_sigma:
This routine implements the Crank-Nicolson finite-difference method with
boundary conditions dray_theoretic_sigma/da=0.

ray_theoretic_beta:
This function implements the Crank-Nicolson finite-difference 
method, with boundary conditions dray_theoretic_beta/da=1. 

eiktam:
The actual computation of times and ray_theoretic_sigmas is done in polar coordinates,
with bilinear interpolation used to map to/from rectangular coordinates.

Authors: CWP: Zhenuye Liu, based on code by Dave Hale, 1992.