GBBEAM - Gaussian beam synthetic seismograms for a sloth model gbbeam syntraces xg= zg= [optional parameters] Required Parameters: xg= x coordinates of receiver surface zg= z coordinates of receiver surface Optional Parameters: ng=101 number of receivers (uniform distributed along surface) krecord=1 integer index of receiver surface (see notes below) ang=0.0 array of angles corresponding to amplitudes in amp amp=1.0 array of amplitudes corresponding to angles in ang bw=0 beamwidth at peak frequency nt=251 number of time samples dt=0.004 time sampling interval ft=0.0 first time sample reftrans=0 =1 complex refl/transm. coefficients considered prim =1, only single-reflected rays are considered ", =0, only direct hits are considered atten=0 =1 add noncausal attenuation =2 add causal attenuation lscale= if defined restricts range of extrapolation aperture= maximum angle of receiver aperture fpeak=0.1/dt peak frequency of ricker wavelet infofile ASCII-file to store useful information NOTES: Only rays that terminate with index krecord will contribute to the synthetic seismograms at the receiver (xg,zg) locations. The receiver locations are determined by cubic spline interpolation of the specified (xg,zg) coordinates. AUTHOR: Dave Hale, Colorado School of Mines, 02/09/91 MODIFIED: Andreas Rueger, Colorado School of Mines, 08/18/93 Modifications include: 2.5-D amplitudes, computation of reflection/ transmission losses, attenuation, timewindow, lscale, aperture, beam width, etc.