754 



EXPLORATION GEOPHYSICS 



sin arc,n = Vk/Vn- With the velocities given above, sin ak,n and cos ak,n 

 have the following values : 



cos flk.n 



V;=S7/oysec .h,'S94 



y^ = esso' 1*1=797 



V3'-7490' fy^S96 



h4'390 



Vs =9170' 



Fig. 458. — Travel-time curve for a. sub- 

 surface section consisting of 5 horizontal 

 layers. 



Successive computations of the layer thicknesses proceed in the manner 

 indicated in the table. The travel-time curve for the five-layer section is 

 shown in Figure 458. 



