868 



EXPLORATION GEOPHYSICS 



explosion sound indicates poor energy transmission and the generation of 

 low frequency waves. An explosion which has a sharp crack or snap 

 usually produces a record of higher frequency waves and is the most efficient 

 for energy transmission. Few general rules can be given for the size and 

 placement of the charge. All this must be worked out empirically for each 

 area and sometimes even for each hole. 



Fig. 542. — Loading deep seismic holes by use of weighted winch lines, a, explosive 

 cartridge; b, weighted tube; c, winch; d, hand control on winch. (Courtesy of United 

 Geophysical Company.) 



The shooting truck often is equipped with a water tank of about 500 

 gallons capacity, dynamite box, cap box, shooting poles and rack, a water 

 pump, and also a power winch for loading deep holes. Figure 543 shows 

 a truck of this type, and the shot-point geyser following a shot. 



This picture illustrates the violation of three safety rules. (1) The 

 magazine doors should be opened only during the short period of time 

 required to remove the necessary explosive for loading the hole. They 

 should not be open during the shooting operation. (2) The explosives 

 should be at least 100 feet from the shot-hole. The truck should be 

 removed to a safe distance. (3) Empty dynamite boxes should not be left 

 on the ground. 



Figure 544 shows a powder magazine trailer and cap magazine. The 

 trailer will hold 3,000 pounds of dynamite and the magazine 500 caps. The 



