Historic Earthquakes

Andreanof Islands, Alaska
1986 05 07 22:47 UTC
Magnitude 7.9

This earthquake caused moderate damage to structures on Adak Island and slight damage on Atka Island. Damage to buildings on Adak Island consisted of cracked masonry and concrete walls, failure of partitions and suspended ceilings, spalling on concrete beams and piers, and differential settlement of house foundations. Soil liquefaction was observed in localized areas of backfilled soil, and sand blows were observed. Laterally spreading cracks and differential ground settlement occurred along a small wharf. This earthquake caused a small tsunami that was recorded throughout the Pacific Ocean.

Abridged from Seismicity of the United States, 1568-1989 (Revised), by Carl W. Stover and Jerry L. Coffman, U.S. Geological Survey Professional Paper 1527, United States Government Printing Office, Washington: 1993.