768 



EXPLORATION GEOPHYSICS 



On combining these relations with the definition of delay time 





one obtains 



Af = 



Af/ COS g 

 V 



Fig. 4G4. — Portion of actual ray path and hypothetical ray 

 path. (After Gardner, Geophysics.) 



The total delay time to a given depth H of the marker horizon is 



AH cos a 



''=1 



V 



and the depth of the horizon is 



H=y AH 



(119) 



(120) 



Equations 119 and 120 constitute a set of parametric equations from which 

 the delay time f corresponding to a depth // of a marker horizon can be 

 obtained provided the quantity AH is known as a function of V. I 



Also, the total offset distance a=2 Ao may be written in the form ' 



a=yAHtana (121) 



Evidently Equations 121 and 119 are a set of parametric equations from 



