736 EXPLORATION GEOPHYSICS 



Continuous Seismic Profiling 



A technique which has recently gained widespread appHcation is the 

 method of "continuous profiHng." In this method the seismometer sta- 

 tions are spaced uniformly along the entire length of a prospect line, being 

 offset a constant distance from the line of shot-points. Shot-points are 

 evenly spaced and intercept a constant number of seismometers. Figure 

 448 shows a specific arrangement where ten seismometers are used.* 



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s e/SMOMerefts 

 S 6 7 6 9 to 



T — OP OOOOOOOOOOOOOOOQ-O 

 I ; "---,_ , -' /' z' 3'.,V s' «' 7'. «3'' 9' lO' 



-i — W-U^l SHOT POIMTS -*^)i('' 7^ 



ABC 



Fig. 448. — Spread for continuous profiling. (Salvatori, Geophysics.) 



From shot-point A, shots are fired to give the first record which comprises 

 traces from seismometer stations 1 through 10 ; for the second record, 

 the seismometers are left in place and a shot is fired at shot-point B. 

 The seismometers are then deposited in stations V through 10' and shot- 

 points B and C are used in succession. Thereafter the entire procedure 

 is repeated for the next interval which starts at C, and so on. 



A section showing the paths of the reflected rays corresponding to the 

 record for shot-point A is shown in Figure 449. Reflecting points on the 



f «' 9 4' S' «■ 



Fig. 449. — Reflected ray paths in continuous profiling; seismometers at 1 . 

 and 1'. ..10'; shot-points at A, B, C. 



reflecting bed are spaced evenly at a distance equal to approximately 

 half the seismometer separation, and, from the sequence of shots and 

 spreads, it is evident that the entire length of reflecting bed is covered 

 to this detail. Moreover, the ray path traversed from shot-point A to 

 seismometer 10 has virtually the same reflecting point as the ray path 

 from shot-point B to seismometer 1. These ray paths would therefore 



* See "Mapping Faults by the Reflection Method," Henry Salvatori, Geophysics 2, 

 No. 4, October, 1937. 



