Jul 12, 2021
Project Cannikin, an underground test of the five-megaton W71 warhead that took place at Amchitka in the Aleutians
The W71 was lowered 6,150 feet (1,870 m) down a 90-inch-diameter (2.3 m) borehole into a man-made cavern 52 feet (16 m) in diameter. A 264-foot-long (80 m) instrumentation system monitored the detonation. The full yield test was conducted at 11:00am local time November 6, 1971 and resulted in a vertical ground motion of more than 15 feet (4.6 m) at a distance of 2,000 feet (610 m) from the borehole, equivalent to an earthquake of magnitude 7.0 on the Richter scale. A 1-mile-wide (1.6 km) and 40-foot-deep (12 m) crater formed two days later.
