vgr (subdirectory with all files)

Constant velocity gradient model.

Demo data files for network ray tracing within Fresnel volumes:

For network ray tracing within Fresnel volumes, dimension MIND in 'net.for' has to be adjusted properly (MIND=1 in the basic version). If there are no structural interfaces in the model, that is also the case of the following data, dimension MICB in 'net.for' may be decreased to NICB=1 to save the memory (MICB=MGRID in the basic version). Dimension MGRID in 'net.for' may be adjusted according to the memory available (MGRID=666666 in the basic version roughly corresponds to 16 MB of RAM). When having adjusted the dimensions in 'net.for', it is recommended to adjust the dimensions in 'netind.for' accordingly. The following data may be run by entering
perl go.pl fv-net.h
from the command line.

vgr-mod.dat

Data for the MODEL package specifying a 1-D constant velocity gradient model used by P.Podvin and I.Lecomte (1991), Geophys.J.int., 105, 271-284.

fv-net.h

SEP history file to perform iterative two-point network ray tracing within Fresnel volumes.
Network ray tracing is first performed in the initial grid, without index file, using input data 'fv-net1.out' and 'fv-net2.out'.
Program 'netind.for' then updates the grid and appends the updated parameters to its input history file. Program 'netind.for' also creates the index file describing the Fresnel volume for the next iteration. The name of the index file is taken from file 'fv-net3.out'. The Fresnel volume corresponds to the two-point travel-time error.
Network ray tracing is then performed in the updated grid, within the Fresnel volume specified by the index file, using input data 'fv-net3.out' and 'fv-net4.out'.
The grid and the Fresnel volume are updated by program 'netind.for', and iterations may continue...

fv-net1.dat

The data for network ray tracing from the first given point (file 'fv-src.dat') to the second given point (file 'fv-rec.dat') during the first iteration when no volume indexing is applied (no index file is specified). Velocities gridded in 'fv-vel.out' are referred. Output files 'fv-rays1.out' containing the two-point ray, 'fv-end1.out' containing the two-point travel time and its error, and 'fv-tt1.out' containing the travel-time field will be generated.

fv-net2.dat

The data for network ray tracing from the second given point (file 'fv-rec.dat') to the first given point (file 'fv-src.dat') during the first iteration when no volume indexing is applied (no index file is specified). Velocities gridded in 'fv-vel.out' are referred. Output files 'fv-rays2.out' containing the two-point ray, 'fv-end2.out' containing the two-point travel time and its error, and 'fv-tt2.out' containing the travel-time field will be generated.

fv-net3.dat

The data for network ray tracing from the first given point (file 'fv-src.dat') to the second given point (file 'fv-rec.dat') during the subsequent iterations. File 'fv-net3.dat' differs from 'fv-net1.dat' only by specifying input index file 'fv-ind.out' generated by program 'netind.for' according to the results of the previous iteration. The numbers of gridpoints in this file are not important. They are updated by program 'netind.for' and new updated file 'fv-net.out' is used for network ray tracing during each subsequent iteration.

fv-net4.dat

The data for network ray tracing from the second given point (file 'fv-rec.dat') to the first given point (file 'fv-src.dat') during the subsequent iterations. The numbers of gridpoints in this file are not important. They are updated by program 'netind.for' and new updated file 'fv-net.out' is used for network ray tracing during each subsequent iteration.