SEEING THROUGH ROCK SALT WITH RADAR

A VHF radar has been used in a salt mine in the Cote Blanche Salt Dome to probe horizontally for the dome flank and vertically for the top of the salt. Discontinuities in the salt's complex electric permitivity caused by anhydrite stringers, shale, sandstone, water, or fractures will caused radar reflections, A narrow beam, ±9 degrees in salt, helps to determine the direction to the discontinuity. The time of the radar reflection determines the range to the discontinuity. The maximum,one‐way penetration was 2040 ft. The radar speed in Cote Blanche salt was measured by timing radar reflections through known distances of salt. The measured radar speed was 188ft/μsec slightly less than the radar speed in pure salt (203 ft/μsec. ). A shear zone in the salt was found to have many discontinuities or radar targets. A discontinuity was detected in a discontinuity about 400 ft above the mine level, but still inside the salt, was also found. The top of the salt dome was detected from several locations in the mine.