Chap. 9] 



SEISMIC METHODS 



543 



by the expressions in the preceding paragraph. Sin 7 = Vo/kp = 

 (v — kh)/kp. Hence, sin ^ = v/pk and s = p arc sin v/pk. Therefore, 



(9-64a) 



and 



tAB — 



Fig. 9-72c. Depth determination in curved-ray method. 



f" ^ = i [cos h" h) - COS k-' h)] 



(9-646) 



The travel time in the underlayer is given by Ibc = {D — 2a) /v2 , where 

 a = V2/k[Vl - (vo/vz)' - Vl - (V1/V2)']. Therefore, the total time 



2 



h = r [cos h~^ (V2/V0) — COS h~^ (V2/V1)] 



D 2 



+ ~ - a Vl - (VoM)'' - Vl - (Vi/V2)^] 



V2 k 



