76 



um fmauacr cmmmL 



It 



MitM rmammr cm/t n 



TMce N< T 



luoo Recent* 4- 



TRANSFORHCR 



%•" 



I^ 



Fig. 12. Block diagram of recording system. 



fracted waves are recorded on a low frequency channel which eliminates the 

 "dangling noise" below 3 cps and the ship noise above 20 cps. The water-borne 

 sounds used in determining the shot-hydrophone distances are recorded on wide 

 bands roughly centered at 100 cps and 1000 cps respectively. The response of 

 the three bands to a constant pressure input to the hydrophone is shown in Figure 

 11. 



3-15 cps 

 High Sensitivity 



3-19 cps 

 Low Sensitivity 



30-200 cps 



500- 3000 cps 

 High Sensitivity 



500 - 3000 cps 

 Low Sensitivity 

 30-3000 cps 

 Low Sensitivity 

 Radio Receiver - 



DIRECT 



WAVE 



BOTTOM 

 REFLECTION 



«;ijv'ii«*f«w" 



-^-'..'i*®—*" 



L 



■!■,(. a ' £.vi 



Bottom Reflection 

 at source 



Tim* in Stconds 



OSCILLOORAM OF EXPLOSIVE WAVES USED IN SEISMIC STUDIES 



Length of three-hydrophone spread - 

 Charge " ^^ lbs. TNT. 

 Shot Distance — 5.5 nautical miles 

 Ocean Depth — 2255 fathoms 



600 feet. 



Fig. 13. Sample oscillogram of a seismic refraction shot in deep water. 



