518 



SEISMIC METHODS 



[Chap. 9 



Combination of two travel-time curves, as in Figs. 9-52 and 9-53, gives 

 the curve for a salt dome or intrusion with vertical flanks (see Fig. 9-39). 



Oiluviil tnd Tertiary Sands and Clap 

 5(7// Dome 



"™N. 



Fig. 9-55. Travel-time curve across salt dome (after Rankiue). 

 I-/5 sec 



5W 



Asmori Limestone 



Fig. 9-56. Refraction profile across strike of Masjid-I-Suleiman anticline, Persia 



(after Rankine). 



In some cases the assumption of a homogeneous overburden, as made 

 here, does not furnish the actual travel times accurately enough. Then 

 an assumption of a uniform increase of velocity with depth is required or 



