/TT°\ 



HYDROPHONE 

 ARRAY 



SURFACE 



BOTTOM 

 SUB- BOTTOM 

 HORIZON i 

 HORIZON 2 



HORIZON 3 



Figure 7. Schematic showing signal paths of a seismic 

 reflection profiler 



section of the subbottom material. However, reflections can appear on the 

 record where there is little significant difference in the lithology of under- 

 lying and overlying material, and significant lithologic differences may go 

 unrecorded due to close similarity of acoustic impedance between bounding 

 units. Because of this, seismic developed stratigraphy should always be con- 

 sidered tentative until supported by direct evidence of lithology from cores. 

 Basic components 



78. Seismic reflection systems are usually composed of four major com- 

 ponents: a source that produces acoustic signals, a power supply to provide 

 energy to the source, a signal processor to amplify and filter return signals, 

 and a recorder to control the initiation and repetition rate of the pulses and 

 display the data in graphic form as it is received. In addition, ancillary 

 components, described later, can be used to increase the quality of the data. 



79. The overall characteristics and capabilities of seismic reflection 

 systems are largely determined by the type of device used to generate the 

 acoustic pulses (acoustic source) and their energy output. Since the intro- 

 duction of seismic reflection techniques, a variety of sources have been 

 developed. Most of these sources use gas, compressed air, electric arcs, or 

 electromechanical and piezoelectric devices to generate the repetitious acous- 

 tic pulses that are used to probe the bottom and sub -bottom materials. These 

 basic types can be obtained in a number of variations having different energy 



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