NOMOGRAMS FOR DETERMINING MAXIMUM ERRORS AND LIMITING CONDITIONS IN SEISMIC REFRACTION SURVEY WITH A BLIND‐ZONE PROBLEM

Nomograms are presented for the determination of the blind‐zone in seismic refraction surveys. The nomograms are calculated for the case where an intermediate velocity is assumed within the blindzone of a recorded refractor which is overlain by a single recorded layer. The nomograms may be used with time‐term or critical distance calculations and yield the depth to the top of the blind‐zone, the thickness of the blind‐zone, and the corrected depth to the recorded refractor. These values represent the maximum or limiting conditions for a layer of the assumed velocity within the blind‐zone.