Abstract

The shooting medium, in seismic reflection surveys on land, in most parts, is relatively unconsolidated. When explosive is blasted in a shot hole, in a relatively unconsolidated medium, a zone of permanent deformation is formed around the hole and a cavity may also be formed around the bottom of the shot hole. If explosive is re- blasted in such a hole, the zone of permanent deformation and cavity formed around the bottom of the shot hole affects (generally assumed to be adversely) energy transmission and frequency content. Zone of permanent deformation is expected to result in improved energy transmission (if cavity formation is little to moderate), whereas cavity formed around the hole bottom may result in higher frequency absorption. Certain areas in north Cambay basin have exhibited improved energy transmission with better or comparable frequency band width on re-blasting of blasted holes.