SPATIAL PROBLEMS IN GEOMETRICAL SEISMICS 67 



muths) of the rays in the second medium which we have found, for a ray 

 with an azimuth of 300° and an azimuth of 305°. We then obtain the pro- 

 jection of the ray on to the horizontal plane in the second medium. As can. 

 be seen from the illustration and also from the values of the direction co- 

 ordinates, the ray under consideration undergoes azimuthal deviation of +5° 

 during refraction. 



Having traced the directions of the rays after refraction in the second 

 medium, we find the trace projection of the intersection of the ray surface 



760 750 740 730 720 710 700 690 680 



Fig. 13. Determination on plan of projection of point of intersection of a ray with 

 a reflecting interface. 1 — structure contours of reflecting interface; 2 — direction of 



incidence of ray. 



with the reflecting boundary. This projection is also found to be the geo- 

 metric locus of the trace projections of the intersection with a reflecting 

 boundary of individual rays of the ray surface, in our case rays with 

 azimuths in the first medium which are 10° from one another. 



The traces of the rays' intersection with the reflecting interface are found 

 to be points on the ray and the interface which have the same depth. These 

 traces are then projected onto the observation plane. We determine the 

 trace projection of the intersection for a ray with an azimuth of 300°. After 

 refraction on the inclined interface at point a, the ray with the 300° azimuth 

 and the 30° angle with the vertical has changed its direction — the azimuth 



