Subsurface Methods as Applied in Geophysics 



1099 



relation would contain a cumulative depth error of over 100 feet per miler 

 This would cause sufl&cient distortion to make a major structure appear 

 as a shelf. Several methods of correcting the effects of lateral variations 

 of velocity have been proposed,"^^ '^^ the correction to be applied to the 

 data being read from correction maps created for certain horizons on the 

 basis of well-velocity information. Gaby '^^ proposed a method of com- 



700O 



R24E 



.9000. 



T 



a9i 



T 

 30 

 S 



R 27E 



Contour Interval 

 100 feet /second 



R28E 



Figure 579. Average velocity at a constant depth of 7,500 feet below base of weather- 

 ing in southeast portion of San Joaquin Valley, California. (Adapted from 

 Stulken. Reproduced permission Geophysics.) 



putations that enables one conveniently to reassign velocity scales for 

 the express purpose of maintaining agreement between seismic interpreta- 

 tions and velocity revisions. For an excellent discussion of the interpreta- 

 tion of data obtained by well shooting, the reader is referred to the 

 papers by Dix.'^''^ 



'^ Stulken, E. J., op. cit. 



'6 Navarte, P. E., On Well Velocity Data and Their Application to Reflection Shooting: Geophysics, 

 vol. 11, no. 1, pp. 66-81, Jan. 1946. 



'^ Gaby, P. P., A New Type of Seismic Cross Section Wherein Accuracy of Representation is 

 Rendered Insensitive to Velocity Error: Geophysics, vol. 10, no. 2, pp. 171-185, Apr. 1945. 



" Dix, C. H., 7'he Interpretation of Well Shot Data, I: Geophysics, vol. 4, no. 1, pp. 24-32, Jan. 

 1939; //.• Geophysics, vol. 10, no. 2, pp. 160-170, Apr. 1945; ///; Geophysics, vol. 11, no. 4, pp. 457-461, 

 Oct. 1946. 



