amchitka island

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Cannikin was detonated on November 6, Amchitka island, Alaska, 1971. It was the largest underground nuclear test in US history. The ground lifted 20 feet caused by an explosive force almost 400 times the power of the Hiroshima bomb. The explosion caused a seismic shock of 7.0 on the Richter scale, causing rockfalls and turf slides of a total of 35,000 square feet Though earthquakes and tsunamis predicted by environmentalists did not occur, a number of small tectonic events did occur in the following weeks, thought to be due to the interaction of the explosion with local tectonic stresses. (Source)