512 



SEISMIC METHODS 



[Chap. 9 



of the waves with the travel times ts and U , a break with the abscissa X3 

 occurs, and the depth dz may be computed as before: 



^3 . /V4 — V3 , a2 — a\ ,__ ^ __ ^^ , d\ 



2 



/ V4 - V3 

 T V4 + V3 



+ -r^ — — (cos j3 — COS 5) + 



sin /3 cos 7 



(cos 



o joosoem tsooiaoo 3000 3500 



Df stance ■ ftrt 



4400 4900 5400 



cos e) 



sm a cos 7 



+ ^2 = ^3. (9-466) 



m^^///ii' jeoo jj; 



4900 



V =^7X30 ^ 

 /t.secr' § 



%!5^;;"<? 



-mi^y/zm vfA^Z/^m^/^' 



/^aious ma(tr/a/ 



Cakulaitd 

 atction. 

 Igntoua 

 rock 

 at 

 JfOO' 



■r + + 



WeU, Imikaw^. 

 igntous roctt 

 at 

 1140' 



+ 4 + 

 + -I- i- 

 t + + + 



Basalt 1 



Fig. 9-50. Refraction profile, calculated section, and results of drilling (southern 

 California). (Adapted from F. Rieber.) 



Again a more convenient method for depth calculation is the use of the 

 travel time corresponding to the ordinate intercept. Then, from eq. 

 (9-46a), with s = 0, da — ^2 — ^2 , and so on. 



m 2/13 , 2^2 s , 2di 



T4 = — cos 7 H cos 6 H cos €. 



V3 V2 Vi 



(9-46c) 



Fig. 9-50 gives an example of a travel-time curve in the three-layer 

 case, shot in one direction only. This profile was made in southern Cali- 

 fornia. The sedimentary section is probably Pico formation with sands 



