Synthetic S-wave seismograms for reflections from the top of the thin fractured sandstone layer modeled using the program ATRAK. The synthetics are generated using ray theory and a 20 Hz Ricker wavelet. The cross-line and in-line records are shown for : (a) no fracturing in the sandstone layer (isotropic,125 ); (b) gas filled cracks; (c) fluid filled cracks.