This is an example how to prepare the optimum initial parameters of Gaussian beams (GBs) for Marmousi model. It is based on the paper 'Optimization of the Shape of Gaussian Beams, Seismic Waves in Complex 3-D Structures, Report 11 (Prague 2001), pp. 181-201'.
To calculate the optimum initial parameters of GBs, compile packages FORMS, CRT and MODEL with parameter MRAM in file 'ram.inc' equal at least to MRAM=8000000. After that, launch history file 'gb-inv.h'. There are two parameters in the file that can be easily edited - CPAR1 and SOBMUL. The position of the source is controled by CPAR1. Smoothing is controled by parameter SOBMUL, repeated several time in history file 'gb-inv.h'. The values of parameter SOBMUL correspond to factors sY and sR (see eqs. 82, 89 and 90 in the paper).
First of all, this history file launches another history file 'gb-opt.h', which is designed to calculate the optimum initial parameters of GBs transformed to initial surface. Calculation of the initial parameters of GBs is performed by program 'gbopt.for'.
After that, the initial parameters of GBs are smoothed (in this case with two iterations).
Then, history file 'gb-test.h' is launched to calculate and plot the widths of Gaussian beams.