Acehtsunami

On March 9, 1957, at 14:22 GMT, an earthquake occurred south of the Andreanof Islands, in the Aleutian Islands of Alaska. A Pacific-wide tsunami was triggered by the earthquake, which had a surface-wave magnitude of 8.3, an epicenter of 51.5° N, 175.7° W, and a focal depth of 33 km. Even though no lives were lost, the Hawaiian Islands suffered the greatest with damage costs approximately $5 million (1957 dollars).

The Island of Kauai, Hawaii, was hit twice as hard by this tsunami than by the Aleutian Islands tsunami in 1946. Houses were washed out and destroyed at Wainiha and Kalihiwai. At Haena, the waves reached heights of 16 m. In addition to that bridges were destroyed and sections of highways were flooded. At Hilo, Hawaii, the run-up was reached 3.9 m and damaged buildings. In Hilo Bay, Cocoanut Island was covered by 1 m of water and the bridge connecting it to shore was destroyed.

Although the northwest side of the Hawaiian Islands received high levels of water, the rest of the islands only received elevated water levels on average of 2 to 3 m. Both the 1946 and 1957 tsunamis occurred in the same general location (the Aleutian Islands). Even though the 1957 earthquake released more energy than the earthquake of 1946. The tsunami generated by this 1957 event caused less damage than the tsunami of 1946. This uncertainty of the potential destructive power of a tsunami forces Pacific Tsunami Warning System to issue warnings even when a tsunami may have little or no effect.