Source: Wikipedia

On March 9, 1957, the Andreanof Islands earthquake with a maximum Mercalli intensity of VIII and a moment magnitude of 8.6 occurred (Severe). It took place south of the Aleutian Islands arc's Andreanof Islands group. The incident happened close to Alaska at the Aleutian Trench, a convergent plate boundary that divides the Pacific Plate from the North American Plate. A tsunami that was basin-wide followed, with Alaska and Hawaii feeling the consequences. Losses totaled about $5 million.

Few instruments were able to capture the shock since it happened before the World Wide Standardized Seismological Network was in existence, and as a result, its mechanism is not well known. With the little information available, some attempt was made to understand the rupture area and the distribution of slip. The 750 mi (1,200 km) aftershock zone was the largest ever recorded, which was one component of the event that was certain.

The Seismic Sea Wave Warning System's prompt warnings are credited with averting more severe damage or fatalities.

The 2,500 mi (4,000 km) Aleutian Subduction Zone is where the Pacific and North American Plates merge. This oceanic trench extends from the Kuril Subduction Zone in the west to the Yakutat Collision Zone in the east. There are right-lateral transform faults at both extremities of the subduction zone, including the Queen Charlotte Fault in the east and a similar structure at Attu Island in the far west.

The earthquake in Alaska seriously destroyed the structures and roads on Adak Island, but no one was hurt. Two bridges and a few structures near the pier that were related to oil and fuel were also damaged. On Umnak Island, a concrete mixer and some docks were misplaced.

Damage was even worse in Hawaii, where two people died indirectly as a result of a pilot and a photographer being killed while trying to capture footage of the tsunami's arrival from an airplane. The waves on the island of Kauai were as high as 52 feet (16 meters). The Aleutian Islands earthquake and subsequent tsunami in 1946 were regarded as having impacts that were roughly twice as powerful. On Oahu's north shore, some 50 residences were inundated, and Waialua Bay was significantly impacted. In Haleiwa, bridges and buildings were also impacted. Over $5 million ($46 million in 2017) worth of damage was incurred overall.