BLIND Z0NE SOLUTION TO THE PROBLEM OF HIDDEN LAYERS WITHIN A SEQUENCE OF HORIZONTAL OR DIPPING REFRACTORS.

For an assumed earth model of plane constant-velocity layers and stepwise increase of velocity with depth, the effect of a blind zone on an interpreted depth section was evaluated by defining and intercept time for a blind zone of assumed or known velocity and by using standard time-term equations for layer thicknesses and depths. The treatment covers an arbitrary number of blind zones embedded within a multi-layer sequence of horizontal or dipping refractors. Model calculations affirm the benefits of this approach compared with previous methods which, in general, have been restricted to the case of two horizontal layers with one intermediate blind zone.