APPLICATIONS OF DIP SHOOTING 129 
It has already been pointed out that due to the custom of trans- 
mitting the seismic waves in alternate directions around the traverse 
most of the errors discussed tend to cancel on alternate shots. A care- 
ful tabulation of the direction of shooting on the traverses inspected 
showed an almost equal distribution of the alternate directions around 
each traverse. Only the effect of “‘side-swipe” on asymmetrical trav- 
erses and rapid horizontal increase of velocity over deep salt domes 
seem likely to produce cumulative errors. 
Cumulative errors should on the average produce maximum mis- 
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Misclosure in Feet 
Fic. 4.—Comparison of length of traverse with amount of misclosure. Chart shows 
no apparent relationship. 
closure on the longest traverses, while non-cumulative errors should 
tend to balance out more perfectly on the longer traverses. The same 
107 traverses shown in Figure 3 were plotted to yield Figure 4. In the 
latter figure the amount of misclosure of each traverse has been laid 
off along the horizontal axis while the length of the trav. se has been 
laid off vertically. An inspectionof the figure shows a scattering of 
points indicating no readily perceptible relation between the length 
of the traverse and the amount of misclosure. It is therefore concluded 
that cumulative errors enter but slightly into the dip-reflection 
method, and that the length of the traverse has little to do with the 
amount of misclosure, except for the cases where the misclosure should 
be explained as follows. 
651 
