UNIVERSAL DIP CHART 

2 Ss Fig. 1 
As can be seen from the above curve (B) in Figure 1, the apparent 
velocity (shooting down dip) follows a smooth curve for increasing 
values of «. 
The curve (A), however, indicates a rapidly increasing velocity 
(up dip) for increasing values of «. This velocity approaches infinity 
for the value of < =@, becomes discontinuous and then negative. <A 
negative velocity would be represented on the time-distance curve by a 
velocity line sloping down toward the abscissa away from the origin, 
e.g.: 
=“, 
Negative 
™ Velcity 
ae 
© — 
RS 
KR 

Fig. 2 
Oistance ———$ 
Physically, a negative velocity would result from shooting up a dip 
of such magnitude that the vertical speeding up would be sufficient to 
cause a shorter total travel time for a longer horizontal distance. Such 
a condition has been met in several instances in shooting a radial profile 
in toward a salt dome. An indisputable example is shown here: 
/8=4194 
wae See 
_——— PO 
Titi Minoo IIT. Io ooome 
\O2259 ce 
"SI See. 
Timing units on original record 0.02 sec. 
Actual Record (reduced with pantograph) 
